Why some doctors do not recommend ACL reconstruction

Marc Darrow, MD, JD.

Injury to the anterior cruciate ligament (ACL) is not the most common of knee injuries but it is certainly the most well known. “ACL tear or ACL rupture” are common, not only in professional sports but also in high school and amateur sports. Recently, a few professional athletes have made stunning and prompt returns to their sports. These are currently considered exceptions. Those who do return, because of the extensive resources available to them at the pro – level, usually do so 9 – 12 months down the road. Those, without the enormous resources of pro athlete services with complete ACL tears or ruptures have less chance. People with ACL injuries do have options to chose from besides surgery. These options typically include therapies to compensate for the ACL damage by strengthening the surrounding areas of the knee. What are the realistic options of returning to sport after and ACL rupture? What are the risks of requiring a second ACL surgery after a graft failure? Are there truly non-surgical options? Let’s look at the research.

Returning to sport after ACL surgery

A January 2022 study (1) suggested that following ACL reconstruction:

about 80% patients return to some type of sport,
but only 65% return to preinjury levels of participation, and
only 55% return to competitive sport.

A September 2024 study (2) looked to predict who would and who would not return to sports following ACL surgery. The researchers looked at several factors including preoperative isokinetic (thigh muscle) strength, treatment of meniscal injuries, left vs. right side injury and graft site were found to predict recovery of more than 85% limb symmetry index (operated side as good as non-operated side) in knee extension and flexion strength. (The threshold for return to sports is generally considered a limb symmetry index of more than 85%.) Despite the numerous factors that were analyzed, the predictive power was moderate and there were other considerations to consider beyond thigh muscle strength.

An April 2024 study (3) investigated the time taken for individuals to return to sport post-ACL reconstruction, assess the rate of re-injury and evaluate the reliability of the International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS) scoring systems in predicting a return to sport at the pre-injury level.

The IKDC is a patient reported assessment that , when results are tallied, offer an functional overall rating. The IDKS asks patients about:

Symptoms such as pain, swelling, stiffness, instability or stability.
the ability to play sport or athletic activity
and knee function.

“The Knee Injury and Osteoarthritis Outcome Score (KOOS) is self-administered and assesses five outcomes: pain, symptoms, activities of daily living, sport and recreation function, and knee-related quality of life.” In 1998, doctors found (4) “the KOOS proved reliable, responsive to surgery and physical therapy, and valid for patients undergoing anterior cruciate ligament reconstruction.” It is considered a standard scoring system today in assessing knee treatment outcomes.

In this April 2024 study of 104 patients who underwent ACL reconstruction, 73% (76 of the patients) successfully returned to sport after ACL reconstruction, with no significant difference being found between professional and recreational athletes .

After reconstruction, 31.7% (33 of the patients) experienced an ipsilateral (same side) or contralateral (other side) ACL tear, with those returning to sport within six months showing a fivefold increase in re-injury risk compared to individuals who returned at eight or 12 months, suggesting a significant association between return duration and re-injury.
The relationship between scoring systems and return to sport at the pre-injury level of performance was analyzed . . . revealing that achieving scores of 85.6 (out of 100) or higher in IKDC or 89 or higher in KOOS (out of 100) meant having a 95% probability of returning to sport at the pre-injury level.

How an ACL tear occurs

Why do some doctors not recommend ACL reconstruction?

Before we continue our discussion about the surgical options, let’s explore the realities of a non-surgical option.

Many orthopedists may not recommend ACL reconstruction because it is not realistic for the patient for various reasons explained below. These recommendations may be made to patients who have an isolated ACL tear. These are ACL injuries that did not include meniscus damage, other ligament tearing, or cartilage tear.

ACL reconstructions may also not be recommended to people who are not sport active or do not have physically demanding lines of work.
Non-operative anterior cruciate ligament treatments may include physical therapy and exercise programs to strengthen the knee and restore function. However without an ACL, there will be instability. As part of the non-operative treatment, the physical therapist may focus on exercise for the patient that will address this instability. Some patients will also have knee braces designed especially if they want to have a somewhat confident knee function in sports.

Surgery may not be necessary to recreational physical activities

Orthopedic surgeons working at some of Turkey’s leading sports medical centers released a paper published in December 2017. (5) Here is what they discovered:

“Our data suggest that early surgical reconstruction may not be a prerequisite to returning to recreational physical activities after injury in patients with ACL tears.”

How did they get to this conclusion?

“Whether surgical or conservative treatment is more effective in allowing patients to return to physical activity after anterior cruciate ligament (ACL) injury is controversial.” The researchers sought to compare mid-term outcome measures between isolated ACL tear patients who underwent reconstruction followed by closed kinetic chain exercises and those who underwent neuromuscular training only.”

“We retrospectively evaluated patients with ACL tears who underwent post-surgery closed kinetic chain strength training after ACL reconstruction (Group A), and patients who only underwent neuromuscular training (Group B) with a minimum follow-up time of 5 years. Surgical techniques, rehabilitation, assessment of subjective knee function, one-leg hop test, assessment of joint position sense, muscle strength, and the health profile of the patient were evaluated.”

Patients in both groups returned to their regular physical activity level after a similar time frame (Group A: average, 12 months; Group B, average, 13.4 months).
No statistical difference was observed between the groups for any of the parameters evaluated, including assessment of subjective knee function, one-leg hop test, assessment of joint position sense, muscle strength, and the health profile.

CONCLUSION: “Our data suggest that early surgical reconstruction may not be a prerequisite to returning to recreational physical activities after injury in patients with ACL tears.”

Findings indicated that there is no certain evidence that ACLR for an isolated ACL tear is superior to nonoperative treatment

An April 2024 study (6) examined the evidence or “lack of evidence regarding the effect of operative versus nonoperative treatment for preventing premature knee osteoarthritis in isolated ACL tears while achieving good functional outcomes.” In this study researchers compared the outcomes of ACL reconstruction to primarily nonoperative management of isolated ACL tears. Pre-results, the researchers hypothesized that the outcomes between treatment types would be similar. In examining previously published data, the researchers came to a low evidence conclusion that “Nonoperatively treated knees showed a trend toward lower odds of developing radiological signs of osteoarthritis; however, surgically reconstructed knees had significantly better stability and a trend toward better but clinically not meaningful Lysholm scores (patient reported outcome score). The qualitative synthesis showed that surgical reconstruction was protective against subsequent injuries but not superior when returning to previous activity levels or various functional tests.

The researchers concluded: “Findings indicated that there is no certain evidence that ACLR for an isolated ACL tear is superior to nonoperative treatment. Clinicians should consider nonoperative treatments with a well-designed rehabilitative program as a primary option. However, these findings must be interpreted with caution because of low study quality and high risk of bias.”

When Surgical Treatment Is Not Recommended for Student Athletes

How many times do I say to a patient, “You may not need ACL reconstruction.” How many times do I hear back, “I have a complete rupture, how can I play sports again with this type of ACL injury?” Perhaps nothing is as sacrilegious to these athletes as the notion that they do not need surgery. One of the arguments opponents have to regenerative medicine is the “complete rupture,” argument preventing return to sports.

A November 2021 study (7) examined student athletes with anterior cruciate ligament (ACL) injuries who returned to sports without reconstruction surgery. What the doctors wanted to see was if the student athletes could continue their sporting activities until the end of their season and whether there was an increase in secondary damage associated with knee instability.

What the study found was

288 skeletally mature patients aged under the age of 25 years old with new-onset isolated primary ACL injuries were included.
Of these, 20 student athletes continued playing sports without ACL reconstruction to try to finish the season and were classified as the early return to sports group; the remaining 268 patients, who immediately quit sports and underwent surgery, were classified as the non- early return to sports group.
Knee symptoms and sporting performance for the rest of the season were assessed for the early return to sports group. The presence of secondary damage, e.g., meniscus injuries and chondral lesions, associated with instability were compared between the two groups.

Results:

Of 20 student athletes who continued playing sports without ACL reconstruction and tried to finish the season, fourteen of them (70%) indicated that their knees had given way during sporting activities, and seven athletes (35%) were unable to complete the season.
Medial meniscus tears significantly increased in the athletes who competed without the ACL surgery with three patients experienced locking of the medial meniscus that required immediate surgery.

Conclusions:

Although return to sports without reconstruction to complete the season may be a reasonable strategy for ACL injury, patients’ self-estimated performance level was low and meniscal and cartilage injury rates significantly increased.

How many partial tears progress to full ruptures in younger patients?

A July 2019 study (8) noted: “A partial ACL injury progressed to a complete ACL tear in 39% of young active patients treated conservatively, with half of the complete tears presenting with a concomitant meniscal lesion at the time of reconstruction. Age s less than 20 years and participation in pivoting contact sports were identified as significant risk factors for progression to a complete tear.” Here are some more observations from this study:

Partial anterior cruciate ligament (ACL) tears are observed in 10% to 27% of isolated ACL tears.
There is currently no consensus on diagnosis and treatment protocols, and the outcomes of nonoperative treatment remain undefined.

In this study a total of 41 patients, all younger than 30 years and active in sports, were diagnosed with a partial ACL tear, with no associated meniscal or chondral lesions on magnetic resonance imaging (MRI). All were assigned to a nonoperative treatment program.

Results:

At an average of 43 months (range, 24-96 months), the partial ACL injury progressed to a complete ACL tear in 16 (39%) patients.
Next, 18 (44%) patients returned to their preinjury level of sports activities.

More ACL partial tear patients returned to sports following conservative care, than ACL patients who’s partial tear progressed to a full rupture.

A ruptured ACL can spontaneously heal. But not for everyone.

An October 2023 paper (9) suggests “satisfactory functional results after spontaneous healing of a ruptured anterior cruciate ligament (ACL)” is possible, but “there is still a lot to understand in how an injured ACL may heal, and therefore ACL injury management should be individualized to each patient and carefully discussed.”

So what about this spontaneous healing? Clinical research suggest many factors that would allow an ACL to spontaneous “rebuild itself.” However, these events are very dependent on part of the ACL and its sheath remaining connected between the femur and the tibia. As the authors of the above paper note: “There is evidence that conservative treatment can be successful in the general population, with some people healing their ACL. This is not the case for elite athletes. The emerging evidence regarding the ability for the ACL to heal is intriguing and may change clinical practice in the future, but we urge clinicians to take these results with extreme caution as this may only be suitable for a very small percentage of the population.”

A February 2023 study (10) continues along these lines by saying: “Many authors have reported cases of spontaneous healing but nowadays it is difficult to predict successful healing of an anterior cruciate ligament rupture and, even more, residual functionality and capability to return to sport.” The researchers here investigated cases of spontaneous healing in a population that received non-surgical treatment after anterior cruciate ligament rupture and to perform an updated review of contemporary literature.

The researchers retrospectively reviewed six patients who suffered from an acute complete anterior cruciate ligament rupture and underwent non-surgical treatment. No specific rehabilitation protocol was prescribed. A new magnetic resonance imaging study was conducted 6 months after the injury for the patients.
The minimum follow-up was 13 months (range 6-20 months). At the last follow-up the mean score on the Lysholm scale was 97 (function score out of 100), the mean IKDC score was 94 (function score out of 100), and the mean KOOS score was 96 (function score out of 100). All patients returned to their own sport activities; no one reported significant differences. The magnetic resonance imaging study at 6 months revealed an end-to-end continuous anterior cruciate ligament with homogeneous signal. No one had any new knee injury at last follow-up.

According to the researchers: “(This study’s) findings show that spontaneous anterior cruciate ligament healing is possible and there are chances of clinical recovery for patients not suitable for surgery. However, there is still a lack of evidence about predictors, clinical outcomes, and adequate rehabilitation protocols.”

How does an ACL heal? Is it all about blood?

In surgery or outside of surgery, any damage to an ACL, the healing process is about blood. Understanding how an ACL heals – even a complete rupture has lead doctors to continuously look at bio-materials – such as the blood platelets or PRP therapy mentioned above. In one case, (11) doctors shared the history of a 12 year old boy who grievously injured his knee after being hit by a car – the boy was also a high level hockey player. What makes this story so amazing is that the knee damage was so severe in regard to broken bones, that an ACL reconstruction surgery had to be postponed until the other damaged healed. When doctors went in 14 months later to start the processes of ACL reconstruction, they found a completely regenerated ACL. The attending doctors point out that the body of evidence says that this should not have happened. The medical literature states a completely ruptured ACL does not heal because blood and healing cells cannot reach it.

Yet, their patient with traumatic knee injury with multiple ruptured ligaments healed over the course of 20 months.

It is likely that bracing associated with the patient’s second surgery and delayed union of his tibial fracture allowed healing tissue to be protected from excessive stress until it remodeled with sufficient strength. It is possible that intra-articular scar formation contributed to his healing capacity. (Possibly the blood scaffold.) At age 14 the boy returned to playing competitive hockey – and two and a half years later – still playing with no adverse effects to his knee.

Surgical choices

ACL reconstruction surgical treatment – Is repair better than reconstruction? Patients tend to have very high expectations prior to ACLR.

In 2019 a study from Oxford University (12) wrote that “patients tend to have very high expectations prior to ACLR, which do not match average outcomes. Of 181 patients who awaited ACLR, all patients expected to have almost normal or normal knee function within 12 months of surgery, 91% expected to return to sport within one year of surgery and 98% expected no or only a slight increased risk of knee osteoarthritis after ACLR. These expectations are not realistic.”

The problems of ACL reconstruction surgery are many. So much so that surgeons are now exploring new surgical repair options. In the medical journal Knee doctors discuss the resurgence of interest in primary anterior cruciate ligament (ACL) repair.(13) This is a surgery that will attempt to fix the remnant or remaining ACL with what is left behind as opposed to using a patellar tendon or tendon autograft.

The first benefit of the primary ACL repair is that this procedure is less invasive than ACL reconstruction. An ACL that can be repaired usually does not need tunnels drilled in bone to thread the ACL graft and screws to hold them down. However, one must remember that the reason transplant became popular was because the primary repair really did not work that well.

In a February 2023 (14) assessment of outpatient data, researchers compared joint laxity and surgical failure reports between repair and reconstruction surgical options. Seven hundred and eight surgical outcomes were assessed on average more than six years after the surgery. This was a younger group of patients, average age about 27 years old, 36% (255 of 708 patients) were women. This study found “ACL reconstruction may yield greater joint stability and lower rate of failure compared with surgical repair.”

If reconstruction is the option, does it matter which graft you use?

A study in The American journal of sports medicine (15) wrote that: “Physicians’ and patients’ decision-making process between bone-patellar tendon-bone and hamstring tendon autografts for anterior cruciate ligament (ACL) reconstruction (ACLR) may be influenced by a variety of factors in the young, active athlete.” The researchers then set out to determine the incidence of both ACL graft revisions and contralateral ACL tears resulting in subsequent ACLR in a group of high school- and college-aged athletes who initially underwent primary ACLR with either a bone-patellar tendon-bone or a hamstring autograft. What did they discover? The odds of ACL graft revision were 2.1 times higher for patients receiving a hamstring autograft than patients receiving a bone-patellar tendon-bone autograft. No significant differences were found between autograft choices when looking at the incidence of subsequent ACLR in the contralateral (the other knee) knee. However they concluded that “there was a high incidence of both ACL graft revisions and contralateral normal ACL tears resulting in subsequent ACLR in this young athletic cohort.”

In September 2024 study (16) investigated patient characteristics that might influence the selection of graft type for anterior cruciate ligament reconstruction. Looking at previously published outcome data, researchers focused on one or more patient characteristics involved in the decision-making process regarding anterior cruciate ligament reconstruction autograft, including the hamstrings tendon, patellar tendon and quadriceps tendon. Out of the 1,977 initial studies, 27 studies were included in this review.

The patella tendon graft seems to be the preferred choice in young patients, females, and athletes-especially those engaged in pivoting sports.
The hamstring graft seems to be the preferred choice in less active and older patients, along with those involved in sports where knee extensors are vital. The hamstring graft is not preferable in patients with a small body height and graft diameter.

An August 2024 study (17) writes: “The choice of graft has been identified as a significant factor affecting the outcome of ACL reconstruction. This study aimed to determine whether allograft or autograft is better for avoiding revisional ACL reconstruction.”

Researchers at The National Health Insurance Service-Health screening database analyzed 146,122 patients who underwent ACL reconstruction surgery from Jan. 1, 2002, to Dec. 31, 2021.
The study was conducted in two groups, autograft or allograft, and the rates of revision ACL reconstruction between the two groups were compared.
- The total of patients with ACL reconstruction was 146,122. Allograft was used in 121,148 patients, and autograft was used in 24,974 patients.
- 9.2% of the allograft group and 8.7% of the autograft group underwent revision ACL reconstruction. 70.0% & 63.6% of patients underwent revision surgery within 1 year in the allograft & autograft groups, respectively. In summary, using autograft in primary ACL reconstruction is helpful in lowering the rate of revision surgery.

An April 2024 study (18) wrote: “There is a convincingly higher re-tear and revision rate in patients who undergo ACLR with allograft than autograft, especially amongst the young, athletic population. Unrecognized Posterior Cruciate Ligament (PLC) injury is a common cause of ACLR failure and current literature suggests concurrent operative management of high-grade PLC injuries. Given the high rates of revision surgery in young active patients who return to pivoting sports, the authors recommend strong consideration of a combined ACLR + Anterolateral Ligament (ALL) or Lateral extra-articular tenodesis (LET) procedure in this population.”

The type of graft recommended for female patients under the age of 25

In March 2022 doctors reported on graft choice recommendations for women 25 years old and younger.(19) They found that bone-patellar tendon-bone autografts showed significantly less graft failure compared with hamstring tendon autografts. However, bone-patellar tendon-bone autografts had comparable patient-reported outcomes compared with hamstring tendon autografts with the available data. The overall state of evidence for graft choice in female patients aged 25 years and younger is low. Future studies should report statistics by age and sex to allow for further analysis of graft choice for this specific population that is known to be more vulnerable to ACL injury.

You already had the ACL reconstruction surgery and your knee is not as strong as you thought? Now what types of injury treatment or options do you have?

You are not alone in asking, doctors are asking the same thing. Now what?

Doctors at the University of Pittsburgh (20) say that despite abundant biological, biomechanical, and clinical research, return to sport after anterior cruciate ligament (ACL) injury treatment remains a significant challenge.

Residual rotatory knee laxity (loose knee) has been identified as one of the factors responsible for poor functional outcome. In this study the doctors simply sort to come up with a scoring system to determine how loose was loose.

We see many patients in our office following ACL reconstruction because of knee weakness and instability. This is not limited to recent surgeries, some of our patients had ACL reconstruction decades ago and have had knee problems since.

The risks for revision surgery: Knee laxity post-surgery

Graft failure is an obvious problem and one that researchers want to help avoid in the future. A problem is that according to an August 2024 study (21), doctors are not sure how to classify exactly what is a graft failure and thereby will have difficulties coming up with treatment options in the future. Two distinctive diagnosis doctors used in numerous studies were “abnormal knee laxity” (80%) and “graft re-rupture” (37.5%). Abnormal knee laxity could include “initial graft tension” where the graft was applied too loose during surgery. The graft remained, but the tension was too loose and the knee remained unstable. As a result meniscus damage post-surgery could occur.

A study looking at the rate and timing of same side ACL revision (22) or opposite knee ACL reconstruction found that in outcomes of 1689 patients who required ACL revision or opposite side reconstruction, found 1018 patients with same side revision surgery (60.3%) and other side reconstruction for 671 (39.7%) patients. Patients returning for same side reconstruction did so sooner than patients needing other knee reconstruction. The overall rate of requiring a subsequent ACL revision was found to be 4.2%.

A March 2022 review study (23) suggests that a loose knee after ACL surgery is a high risk indicator of revision surgery. In this study, 17,114 Dutch patients who had ACL reconstruction were placed into three groups on the basis of objective side-to-side differences in sagittal (right or left side) laxity one year after surgery: Group A (laxity less than 2 mm), Group B (3-5 mm) and Group C (laxity more 5 mm).

The main outcome measure was revision rate within 2 years of primary surgery.

Results: The study found the risk for revision surgery was more than five times higher for Group C (high level laxity) than for Group A (low level laxity). These results indicate that increased post-operative sagittal laxity is correlated with an increased risk for revision surgery and might correlate with poorer knee-related quality of life, as well as a decreased function in sports. The clinical relevance of the present study is that high knee laxity at 1-year follow-up is a predictor of the risk of revision surgery.

A July 2024 study (24) assessed the association between knee laxity 6 months after primary ACLR was associated with the 1-, 2-, and 5-year subjective knee outcomes or revision ACLR at a 5-year follow-up.

The study group was patients who underwent primary ACLR with a hamstring tendon autograft with no concomitant ligamentous injuries
Anterior knee laxity was assessed 6 months postoperatively.
The Knee injury and Osteoarthritis Outcome Score (KOOS) was collected preoperatively and 1, 2, and 5 years postoperatively.
A total of 4697 patients (54.3% male) were included.
A high grade of postoperative knee laxity 6 months after primary ACLR was associated with an increased hazard of revision ACLR within 5 years.

Knee laxity in athletes following ACL surgery: The problem of a loose anterior cruciate ligament graft causing the need for a revision ACL surgery reconstruction

A 2019 sports medicine study (25) examined a second or revision ACL surgery’s ability to fix this looseness.

The study authors examined:

Patients who underwent primary and revision ACL reconstruction.
Inclusion criteria were: same patients who underwent primary hamstring tendons and revision bone-patellar tendon-bone autograft ACLR, no associated ligament injuries and no contralateral ACL injuries/reconstructions.
The cause of revision ACLR was graft rupture for all patients.
A total of 118 patients with primary and revision ACLR arthrometric laxity measurements were available.

The mean preoperative and postoperative anterior side-to-side difference values were not significantly different between primary and revision ACLR. However, primary ACLR showed a significantly higher frequency of postoperative anterior side-to-side difference difference compared with revision ACLR.

Conclusions: “The findings of this study showed that anterior knee laxity is restored with revision bone-patellar tendon-bone autograft ACLR after failed primary hamstring tendons autograft ACLR, in the same cohort of patients. However, revision ACLR showed a significantly inferior functional knee outcome compared with primary ACLR. It is important for clinicians to inform and set realistic expectations for patients undergoing revision ACLR. Patients must be aware of the fact that having revision ACLR their knee function will not improve as much as with primary ACLR and the final postoperative functional outcome is inferior.”

Professional basketball players

A March 2024 study (26) of 38 ACL injuries in professional male European basketball leagues from the 2013-2014 to 2019-2020 seasons found most injuries were indirect contact injuries.

More injuries occurred while attacking (25 injuries 69%) than defending (11 injuries, 31%).
There was 1 (3%) direct contact injury, 21 (58%) indirect contact injuries, and 14 (39%) noncontact injuries.
Most injuries (83%) occurred during 3 main situations: offensive cut, landing from a jump, and defensive cut.
Half of the injuries occurred during the first 10 minutes of effective playing time. More injuries occurred in guards (58%), and 73% of all injuries occurred in the scoring zone.

Doctors at New York University (27) examined National Basketball Association players (NBA) to see what type of impact ACL reconstruction had on their careers. At the forefront non-professional athletes need to understand that these players have huge medical and training resources behind them. Even with these resources – here is what the NYU doctors found:

The players: Seventy-nine players (80 knees) with acute ACL tears in the NBA between the 1984-2014 seasons.
The study: Pre- and post-injury performance outcomes including seasons played, games played, games started, minutes per game, points per game, field goals, 3-point shots, rebounds, assists, steals, blocks, turnovers, personal fouls, usage percentage and player efficiency ratings were compared .

The findings:

Sixty-eight of seventy-nine players (86.1 %) returned to play in the NBA following ACL reconstruction.
Many did not last – “There was a significantly higher rate of attrition from professional basketball for players with a history of ACL reconstruction.”

NFL wide receivers were not as good after ACLR

A February 2021 study (28) of wide receivers playing in the National Football League who had an recovered from ACLR surgery found that many of these players did not return to pre-injury form. In this study team doctors examined the time to return to play and evaluate the performance level in wide receivers in the National Football League following anterior cruciate ligament (ACL) reconstruction.

A total of 29 wide receivers in the National Football League who underwent ACL reconstruction between 2013 and 2017 were included in the study.

Of the wide receivers, 9 of 29 (31%) did not return to play in a regular season game following ACL reconstruction.
For players who did return to play, 20 of 29 (69%), the average time was 10.9 months.
When the researchers compared the ACL tear group with the matched control cohort, players with ACL tears ended their careers on an average of 1.9 seasons earlier and also played less than half the number of games.
Those that returned to play also saw decreased performance statistics in targets, receptions, receiving yards, and touchdowns.

Soccer players were not ready to return from ACL reconstruction

A May 2021 paper (29) suggested that while the effects of exercise on anterior knee laxity and anterior knee stiffness have been documented in healthy participants, only limited evidence has been provided for surgically treated patients (athletes) cleared to return to sports after anterior cruciate ligament (ACL) reconstruction (ACLR). The purpose of this study then was to to determine if 45 minutes of a soccer match simulation lead to acute (beneficial) changes in anterior knee laxity and anterior knee stiffness in soccer players returning to sport within 12 months after ACLR. The researchers thought that the reconstructed knee of the ACLR group would exhibit an “altered” response to sport-specific exercise. Altered meaning less successful.

A total of 13 soccer players cleared to return to sport after ACLR and 13 healthy control soccer players were recruited for the study.
Results: Soccer players at the time of return to sport after ACLR showed an altered mechanical response to a sport-specific match simulation consisting of bilaterally unchanged anterior knee laxity and anterior knee stiffness.
Clinical relevance: Soccer players showing altered anterior knee laxity and anterior knee stiffness in response to exercise after ACLR may not be ready to sustain their preinjury levels of sport, thus potentially increasing the risk of second ACL injuries.

Jumping weakness after ACL reconstruction

A May 2022 study (30) suggested that single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes. Here is what these researchers wrote: “Vertical jump performance (height) is a more representative metric for knee function than horizontal hop performance (distance) in healthy individuals. It is not known what the biomechanical status of athletes after anterior cruciate ligament (ACL) reconstruction (ACLR) is at the time they are cleared to return to sport or whether vertical performance metrics better evaluate knee function.” Here is what the researchers found: Jump performance, assessed by jump height and Reactive Strength Index, was significantly lower in the involved (ACL reconstructed knee) than the uninvolved limb and controls, with large effect sizes. During vertical jumps, male athletes after ACLR at return to sport still exhibit knee biomechanical deficits, despite symmetry in horizontal functional performance and strength tests. Vertical performance metrics like jump height and Reactive Strength Index can better identify interlimb asymmetries than the more commonly used hop distance and should be included in the testing battery for the return to sport.

A July 2022 study (31) asked if core stability training improved hopping performance and kinetic asymmetries during single-leg landing in anterior cruciate ligament reconstructed patients? The researchers noted that core stabilization is common within rehabilitation, but its influence on hopping performance and single-leg landing kinetics among athletes post-ACLR is unclear. After testing twenty-four male professional athletes who had ACL reconstruction surgery for improvements following an 8-week core stability exercise program. The study findings indicate the positive effect of core exercise on improving and balancing movement in the operated leg compared to the non-operated leg.

A March 2023 study (32) of 40 patients who underwent ACLR 6 months before (18 females/22 males about 19 years old) demonstrated knee-avoidant jumping mechanics and had significant reductions in knee joint power (quadricep strength) on the surgically repaired limb side.

Revision ACL Reconstruction can fail because of a loose knee after ACL Reconstruction

A 2020 sports medicines study (33) takes us all the way through the three stages, loose knee after ACL Reconstruction, ACL Reconstruction Revision, and ACL Reconstruction Revision Failure. The summary of this study states: “The most important finding of this study was that preoperative medial knee instability is a risk factor for revision ACL Reconstruction and should be adequately addressed at the time of revision ACL Reconstruction. This study demonstrates the largest revision ACL Reconstruction patient group with pre- and postoperative clinical examination data and a follow-up of 2 years published to date and it indicates that preoperative knee instability is an important factor for the treatment strategy of revision ACLR. Medial knee instability, high-grade anterior knee instability and increased posterior tibial slope are risk factors for failure of revision ACLR and should be addressed at the time of revision surgery.

We see many patients following an ACL reconstruction surgery who continue to feel a “certain weakness” or a “looseness” in their knee they were not expecting following the surgery and the extensive sports medicine rehab program they had gone through. Prior to the ACL surgery, most were made aware that there was a chance the graft would fail or that they would not be able to resume activities at the level that they wanted to. For most they had hoped that this would not be the case for them.

We will also be contacted by the parents of a high school age athlete who has already had the ACL reconstruction surgery, some with leading sports medicine specialists with the hopes that the surgery will allow them to continue their high school and college sports career. These parents are now concerned that their son or daughter has complained about their knee giving way and a follow up MRI revealed “a high signal” or an image of some type of deficient in the ACL graft. Now they are back at the sports medicine specialists look for revision surgery.

The problem of a “slightly loose” bone-patellar tendon-bone graft

People do have loose knees after ACL reconstruction. This is pointed out by a sports medicine study from March 2021. (34)

“In spite of supposedly successful surgery, slight residual knee laxity may be found at follow-up evaluations after anterior cruciate ligament reconstruction (ACLR), and its clinical effect is undetermined.”

In this sports medicine study, 234 soccer, team handball, and basketball players undergoing ACLR using bone-patellar tendon-bone graft. Using various tests, players were divided into post-surgical groups of “tight” ACL and “slightly loose” ACL. What these researchers identified was that the tight graft people and the loose graft people, functioned about the same sports level. At least for a little while. What happened?

“The rate of return to pivoting sports was 74% among athletes with tight grafts and 70% among those with slightly loose grafts. Also, return to preinjury level of sports was similar between those with slightly loose and tight grafts (40% vs 48%, respectively), but median duration of the sports career was longer among patients with tight grafts: 6 years vs 2 years.

Five slightly loose grafts (28%) and 6 tight grafts (5%) were classified as failures after 2 years.

A slightly loose graft at 6 months after ACLR increased the risk of later ACL revision surgery and/or graft failure, reduced the length of the athlete’s sports career, caused permanent increased anterior laxity, and led to an inferior Lysholm score (a test measuring knee function and pain symptoms).”

The researchers of this study pointed out the there was not much difference between what they considered a “slight loose” graft compared to a tight graft. To patients needing a second ACL reconstruction it made all the difference.

Sports medicine dilemma: The graft did not take.

A May 2021 paper (35) suggested that after everything else is reviewed, from surgical technique and rehabilitation techniques, graft failure maybe simply a case that the graft did not take. These are some of the points the researchers stressed:

The graft failure rate after ACLR is still relatively high despite advances in surgical techniques and optimizing rehabilitation protocols, and the reason may be because of unfavorable healing process.
The true incidence of ACL graft failure after implantation is unknown at present although as high as 24.4% has been reported.
A study by the University of Pittsburgh showed that after single-bundle ACL reconstruction, the most common rupture pattern seen at the time of revision surgery is proximal (mainly at the attachments) rupture, followed by mid-substance rupture. (The graft is gradually or acutely cut in half by the lateral femoral condyle or bottom of the thigh bone).
They also classified the mechanisms of ACL graft failure as related to
- (a) surgical technique;
- (b) graft incorporation; and
- (c) trauma.
Since sports medicine advances have been made in surgical techniques and rehabilitation methods, when graft failure happens following ACL reconstruction without traumatic events, problematic graft healing should be considered. (The graft did not “take.”)

Does early-stage rehabilitation improve outcomes?

An Octobers 2023 study (36) wrote: “Outcomes following anterior cruciate ligament reconstruction (ACLR) need improving, with poor return-to-sport rates and a high risk of secondary re-injury. There is a need to improve rehabilitation strategies post-ACLR, if we can support enhanced patient outcomes. . . Early-stage rehabilitation is the vital foundation on which successful rehabilitation post-ACLR can occur. Without high-quality early-stage (and pre-operative) rehabilitation, patients often do not overcome major aspects of dysfunction, which limits knee function and the ability to transition through subsequent stages of rehabilitation optimally.”

The researches suggested doctors look at the six main challenges following ACLR

pain and swelling;
knee joint range of motion;
arthrogenic muscle inhibition and muscle strength;
movement quality/neuromuscular control during activities of daily living
psycho-social-cultural and environmental factors and
physical fitness preservation.

Factors effecting rate of recovery

A March 2022 study (37) looked at 245 patients who had ACL reconstructive surgery and divided the patients into three post-surgical recovery groups.

Group 1 had improvement from preoperative to 1-year follow-up, with sustained improvement from 1-to2-years postoperatively, consisted of 77.1% of the study population. This group represent 189 of the 245 patients.
Group 2, demonstrated functional improvement between 1-and 2-year follow-up. This group represented 10.2% of the study population (25 of the 245 patients), and,
Group 3, demonstrated slight improvement at 1-year follow-up with a subsequent decline in knee function scores between 1-and 2-year follow-up. This groups represented 12.7% of the study population (31 of the 245 patients).

Revision surgery, psychiatric history, preoperative chronic knee pain, subsequent knee injury within follow-up were the predictors of group 2 and group 3 rate of recovery patterns.

A September 2023 study in the journal Cureus (38) found female patients and those told that they will need another ACL surgery are at increased risks of postoperative depression/anxiety. Nearly one in seven young females are diagnosed with depression/anxiety after ACLR. Similarly, a greater proportion of patients who suffer a secondary ACL surgery are subsequently diagnosed with depression/anxiety.

More knee reinjuries after ACL reconstruction compared to nonsurgical treatment of the ACL.

An October 2024 study (39) reviewed patient data from 275 patients (52% females, average age 25) about knee reinjuries and surgeries aiming to describe recovery after an acute ACL injury treated according to clinical routine. At 2 years after injury, 169 (61%) had undergone an ACLR.

Thirty-two patients sustained reinjuries within 2 years; 6 in the non-ACLR (surgery) group, and 26 in the ACLR group (7 before and 19 after ACLR).
Twelve patients in the ACLR group sustained a graft rupture and three did an ACL revision.
Patients with non-ACLR, aged 21-25 years, had a 5.9-fold higher risk for reinjury than those aged 15-20 years.
Twenty-four patients had surgery in the non-ACLR group and 36 patients in the ACLR group (excluding primary ACLR), where six were before ACLR and 30 were after ACLR.

ACL reconstruction re-rupture – blame it on the tunnels

A May 2021 paper (40) examined the problems of rupturing the ACL graft.

“Re-injury rates following reconstruction of the anterior cruciate ligament (ACL) are significant; in more than 20% of patients a rupture of the graft occurs.

One of the main reasons for graft failure is malposition of the femoral tunnel. The femoral origin of the torn ACL can be hard to visualize during arthroscopy, plus many individual variation in femoral origin anatomy exists, which may lead to this malpositioning.”

To possible solve this problem it is suggested that MRIs be taken before the ACL reconstruction with the purpose of try to pinpoint the footmark of where the drilling should take place in the bones. The study writes: “a preoperative MRI is needed to identify the patient specific femoral origin of the ACL. The issue here is that there may be a difference in the reliability of identification of the femoral footprint of the ACL on MRI between different observers with different backgrounds and level of experience.”

A May 2021 (41) continued this line of suggestion. In this retrospective study of 58 patients with successful primary ACL reconstruction compared with 59 patients with failed ACL reconstruction, anterior and proximal (high) femoral tunnels for ACL reconstruction were shown to be independent risk factors for ACL revision surgery. As revision ACL reconstruction is associated with patient- and economic burden, particular attention should be given to achieving an individualized, anatomic primary ACL reconstruction. Surgeons may reduce the risk of revision ACL reconstruction by placing the center of the femoral tunnel within the anatomic ACL footprint.

A June 2023 study (42) examined the bone landmark positioning method used to position the femoral tunnel during the anatomical reconstruction surgery in patients with anterior cruciate ligament (ACL) rupture. Eighty-four eligible patients (84 knees) were included in this study. The goal of the study was to see if the boney landmarks put the tunnels is the right position.

Twenty-two and 62 of the patients were categorized in the good and poor position tunnel groups, respectively, and the rate of good position was 26.2%.
One year later, outcomes were significantly better in the good tunnel position group.
In most patients in this study, “the bone tunnels were found to be distributed in and beyond the normal range using the bone landmark method to position the femoral tunnel in the single-bundle anatomical reconstruction of ACL, while the rate of good bone tunnel position was low. The knee joint function scores and stability were lower in patients with poor position of the femoral tunnel.”

ACL reconstruction re-rupture – blame it on a missing meniscus and ligament instability injury treatment

In a December 2021 paper (43) orthopedic surgeons created a comprehensive list of degenerative knee problems that doctors should look for which could cause or did cause ACL re-tear and re-rupture. The study authors found that medial and lateral meniscectomies, peripheral meniscus tears, medial meniscus ramp tears, lateral meniscus root tears, posterolateral corner injuries, medial collateral ligament tears, increased tibial slope and valgus and varus alignment had a significant impact on ACL forces and related knee kinematics and should be looked for if the patient wanted to have a revision surgery to prevent another graft failure surgical treatment.

An August 2023 study (44) on surgical techniques suggests that up to 8% of patients with anterior cruciate ligament (ACL) tears can present with a combined medial meniscal ramp lesion (MMRL) and lateral meniscus root tear (LMRT). Medial meniscal ramp lesions (MMRL) and lateral meniscus root tears (LMRT) often are missed preoperatively and can increase the risk of ACL graft failure if left untreated.

A January 2024 study (45) suggested that doctors could better identify patients with ACL and meniscus damage with a high-grade Lachman’s exam (physical examination), specifically in males who had higher risk of having an ACL tear with a concomitant medial meniscus ramp tear. The researchers suggest that an ACL tear with concomitant medial meniscus ramp tear may be better diagnosed based upon the clinical evaluation rather than other secondary radiological findings.

Meniscus injury and tears after ACL reconstructive surgery

A December 2021 editorial in the medical journal Arthroscopy (46) discussed whether or not a meniscus tear should or should not be treated at the time of an ACL surgical treatment. “Meniscus tears seen at the time of anterior cruciate ligament reconstruction are usually asymptomatic, and treatment varies greatly between surgeons, with meniscus repair being used for tears that could be left in situ (as it was). Recent outcome studies of most types of lateral meniscus tears show that leaving the tears in situ can give equal or superior results. Meniscus repair being performed for degenerative medial meniscus tears does not give better results than removing the tears. As an alternative to repair, trephination (a method of poking tissue to draw blood) through the meniscus into the peripheral capsule can create many bloody channels to promote healing. Long-term follow-up of meniscus treatment with anterior cruciate ligament reconstruction can help us understand outcomes and prevent us from overtreating tears.”

The ACL surgery caused meniscus damage

A November 2022 study (47) wrote of the ACL surgery causing meniscus damage: “Iatrogenic posterior meniscal root avulsions after malpositioning of the transtibial tunnels during anterior cruciate ligament (ACL) reconstruction can account for poor long-term outcomes seen in some patients following ACL reconstruction. . . .Clinicians treating patients with a history of cruciate ligament reconstruction presenting with postoperative pain and instability should consider this pathology in their differential diagnosis.”

Tunnel placement again

A February 2024 editorial in the journal Arthroscopy (48) wrote: “The number one cause of failure is a misplaced ACL femoral tunnel. Tunnel malposition leads to a higher incidence of postoperative meniscal lesions, inferior clinical outcomes, and higher revision rates.”

ACL in the older athlete

In the last two decades, there has been a movement towards performing ACL surgery in the older athlete where in the past athletes were told ACL surgery would not be recommended because of their age and the recovery time needed.

A September 2024 study (49) in ACLR with bone-patella tendon-bone grafting patients examined if age made a difference in surgical success. Patients were divided into 4 groups: below 40 years, 40-49 years, 50-59 years and over 60 years.

The IKDC (function) score showed significantly poorer scores in the 50-59 years and over 60 years group than in the younger groups, however in 83 % and 66 % of cases reached normal or nearly normal grades, respectively.

A September 2024 (50) study that compared ACLR with allograft or autograft in middle age patients found similar short-term patient reported outcomes, however, re-rupture rates were significantly higher in the allograft (donated) cohort than the autograft cohort.

Post-traumatic osteoarthritis

A November 2023 study (51) found older and overweight patients to have higher risk factors for post-traumatic osteoarthritis because of cartilage degeneration and high mechanical force (weight) damaging the sub-chondral of femoral and tibial bones, respectively. Patients with ACL injuries that caused meniscus tear and cartilage defects had a higher risk of getting post-traumatic osteoarthritis than those with a sole ACL injury after the ACL reconstruction.

Psychological readiness. Is it a factor for return to sports after ACL reconstruction?

An April 2024 study (52) examined psychological readiness as an important consideration for athletes and clinicians when making return to sport decisions following anterior cruciate ligament reconstruction (ACLR). Researchers assessed data from 83 studies (78% high risk of bias). Evidence certainty was ‘weak’ or ‘limited’ for all analyses. Overall, “psychological readiness to return to sport appears to improve early after ACL injury, with little subsequent improvement (being any more confident in return to sports) until more than 2-years after ACLR. Longer time from injury to surgery, female sex and older age might be negatively related to Anterior Cruciate Ligament-Return to Sport after Injury scale (ACL-RSI) scores 12-24 months after ACLR.”

A September 2024 study (53) investigated whether patients who have undergone ACL reconstruction and have a higher preoperative psychological competitive ability have a better emotional status preoperatively and six months postoperatively. The possibility of returning to sports was compared between the two groups.

Eighty-four patients were included and divided into better emotional status and lower emotional status. Vigor-activity and friendliness were significantly higher in the better emotional status group than in the lower group preoperatively. The difference was even greater at six months after ACL reconstruction.
In addition, the better emotional status group showed significantly better results postoperatively for fatigue-inertia and total mood disturbance.
Rates of return to sports did not differ significantly between the two groups (56.5% vs. 54.1%). The psychological competitive ability did not affect the rate of participation in the entire practice at six months postoperatively.

How do people with knee symptoms describe their quality of life and experiences 5 to 20 years after anterior cruciate ligament reconstruction? What factors impact upon the quality of life of these people?

Here is what the patients told doctors in the Archives of orthopaedic and trauma surgery (54) Four consistent themes emerged from the interviews as common determinants of quality of life following ACL reconstruction: physical activity preferences; lifestyle modifications; adaptation and acceptance; and fear of re-injury.

All participants described the importance of maintaining a physically active lifestyle and the relationship between physical activity and quality of life.
Participants who suppressed or overcame re-injury fears to continue sport participation described experiencing a satisfactory quality of life while taking part in sport despite knee symptoms.
For some participants, resuming competitive sport resulted in subsequent knee trauma, anterior cruciate ligament re-rupture or progressive deterioration of knee function, with negative impacts on quality of life following sport cessation.
Participants who enjoyed recreational exercise often adapted their lifestyle early after ACLR, while others described adapting their lifestyle at a later stage to accommodate knee impairments; this was associated with feelings of acceptance and satisfaction, irrespective of knee symptoms.

Here is the reality of it all – knee problems continued well after the ACL Reconstruction.

Regenerative medicine injections

What about older patients? PRP injections or ACL Surgery?

Here we will briefly touch on the non-surgical option of PRP, especially in the older patient. PRP treatments involve collecting a small amount of your blood and spinning it in a centrifuge to separate the platelets from the red cells. The collected platelets are then injected back into knee to stimulate healing and regeneration. PRP injections do not grow a new ACL, they strengthen the other support structures within the knee to help offset ACL deficiency.

An August 2022 study (55) compared PRP injections to ACL reconstructive surgery outcomes in older patients. These are the findings: “In old patients with ACL rupture, surgery is not recommended due to the person’s low level of activity and knee osteoarthritis. Platelet-rich plasma (PRP) is a good treatment option in inflammatory cases in orthopedics.” This study was to assess and comparison of the effect of PRP and arthroscopic surgery on anterior cruciate ligament rupture.

100 patients were randomly divided into two groups.
- The first group of patients underwent ACL tendon repair surgery by arthroscopy and tendon graft.
- The second group were treated by PRP injection.
- Patients in both groups had significant improvements in decreased pain severity after 14 months. The surgical treatment group had lower pain and higher range of motion compared to PRP group.

For the older patient PRP presented a non-surgical option that was comparable to ACL reconstruction.

Injections post-ACL Reconstruction. What’s the evidence?
Researchers did not find any clinical benefit of intraarticular hyaluronic acid injection following ACLR surgery

A March 2022 paper (56) examined the problems of pain, swelling and joint stiffness following arthroscopic ACL reconstruction (ACLR) surgery that according to the paper ” restrict early return to sports and athletic activities. The patients often receive prolonged analgesic (pain relief) medications to control the inflammatory response and resume the pre-injury activities.” The goal of this study was to evaluate the safety and efficacy of intraarticular hyaluronic acid injection following ACL reconstruction (ACLR).

The researchers examined post published medical research and identified four studies that would best answer their question on the effectiveness of intraarticular hyaluronic acid injection following ACL reconstruction (ACLR).

There were 182 patients in the intraarticular hyaluronic acid injection group and 121 patients in the control group. In comparison analysis the researchers found: “Although the individual study demonstrated a short-term positive response regarding pain control and swelling reduction, the pooled analysis did not find any clinical benefit of intraarticular hyaluronic acid injection following ACLR surgery.”

A September 2024 study (57) writes: “Emerging trends and future directions in ACL reconstruction are centered on advancements in biological augmentation, innovations in surgical techniques, and the need for comprehensive long-term outcome studies. Biological augmentation methods, such as platelet-rich plasma and stem cells, are increasingly recognized as promising options for enhancing ACL repair and reconstruction. These biological agents aim to create a more conducive healing environment for the graft, which could lead to improved clinical outcomes.”

PRP Injections

An August 2023 study (58) suggested PRP Injections (discussed above) may help accelerate healing after ACL reconstruction. In this study, 80 patients who underwent ACL reconstruction were randomly assigned to receive either PRP or standard treatment. After 6 months, the group treated with PRP showed improved healing and better knee function compared with the non-PRP group. These findings suggest that PRP can help accelerate ACL healing and improve outcomes for patients. A 2022 paper did not support the use of PRP. (59) The main finding was that only a few publications demonstrated a positive effect of PRP on accelerating the maturation process of tendon graft and healing processes on bone tunnel and the harvest site of autologous graft, and the clinical outcomes could hardly be significantly improved following application of PRP.

In a January 2024 study (60), doctors administered PRP therapy within six weeks after ACL injury in patients who expressed the desire for an early return to sports through conservative care. After the treatment, patients wore a simple brace that limited deep flexion but placed no restrictions on weight bearing. Four months was the standard goal established for returning to pre-injury condition. The average patient age was 32.7 years and the average treatment was 2.8 PRP sessions.

MRI evaluations confirmed that ligament continuity was regained in all cases. All the patients returned to their pre-injury level in an average of 139.5 days, but there was one instance of re-rupture following the return to sports.

Stem Cell Therapy for ACL tears

Are stem cells an option to ACL reconstruction? Mesenchymal stem cells are injected into the area of the ACL tear. The theory is that the stem cells can deliver and help produce healing factors to repair damaged cells and stimulate tissue regeneration.

In December 2019, a study from the Mayo Clinic (61) suggested that stem cell therapy may offer a viable enhancement to post-surgical ACL reconstruction repair. They write, “As regenerative medicine continues to rapidly evolve, the use of stem cells in ligament repair and reconstruction continues to be investigated and grow. Various stem cell preparations are available in clinical practice . . .To date, there is a relative paucity of high-level evidence for the use of stem cells in ligament surgery and healing; however, early human and animal results support the reparative and immunomodulatory potential of stem cells as an evolving therapeutic meriting further investigation. . .improved outcomes spanning from higher patient-reported outcome scores to magnetic resonance imaging evidence of ligament healing in the setting of anterior cruciate ligament tears.”

The idea of improvement to surgery is expressed in many patients we see for ACL tears and knee problems who are unfortunately on their second or even third ACL reconstruction surgery recommendation. They are weighing their options knowing already what a surgery and rehabilitation will be like. For them the appeal of surgery has lost some luster.

During the surgery: PRP and bone marrow aspirate used during ACL reconstruction

A January 2024 study (62) examined the outcomes of bone marrow aspirate concentration and PRP applied during ACL reconstruction. (The study”indicated the limited enhancing effect in clinical function, (ACL) graft maturation and tendon–bone interfacial healing, with only significant knee laxity improvement in the bone marrow aspirate concentration + PRP group at 24 weeks compared with the control group (no biologic augmentation).

Summary

The ACL’s main function is to keep the thigh and shin bones aligned within the knee. When the ACL is not there, the job of knee stability is then taken up by the tendons and other ligaments of the knee. Because this was not their intended job, osteoarthritis can develop more rapidly. It may be possible however to strengthen these connective tissues in the ACL deficient knee (nonsurgically treated patients) and allow the athlete to return to sport. Please email below your case or questions so we can assess if this may be a realistic options for you.

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