Marc Darrow, MD
Many people today are exploring meniscus surgery alternatives. One reason is that there is significant and controversial research to suggest that not only will meniscus surgery NOT help them, but is some instances, the surgery may leave them worse off. But what if you have been told that surgery is the only option? Research presented in this article may provide you with an understanding that perhaps there are more options than just surgery.
When knee pain from meniscus damage is symptomatic, it represents a challenge since arthroscopic surgery provides unpredictable results
Many people have very successful surgeries. Many people do not. This is the definition of unpredictable results. That is a general statement, often people and doctors go into a surgery with a realistic expectation that the surgery will not be that successful. However that is a risk that some people are willing to take in an attempt to get better knee function.
A December 2021 paper (1) offers this assessment of meniscus damage treatment: “When symptomatic, (knee pain and functional limitations) represents a challenge since arthroscopic surgery provides unpredictable results: recent evidence has shown that partial meniscectomy is not better than conservative management up to 2 years of follow-up, and the removal of meniscal tissue may accelerate osteoarthritis progression toward osteoarthritis. Intra-articular injection of corticosteroids or hyaluronic acid may help in providing temporary symptomatic relief, but no influence should be expected on the quality of the meniscal tissue.”
Arthroscopic surgery provides unpredictable results
A June 2020 (2) review of meniscus tear treatments offered this assessment of treatment options: “. . . recent studies have conclusively shown that outcomes after an Arthroscopic partial meniscectomy are no better than the outcomes after a sham/placebo surgery. Meniscal repair (as opposed to meniscus tissue removal) is now being touted as a viable and effective alternative. Meniscal repair aims to achieve meniscal healing while completely avoiding the adverse effects of partial meniscectomy. . . It is now increasingly recommended to attempt meniscal repair in all repairable tears, especially in young and physically active patients. Partial meniscal implants have also shown excellent outcomes in long-term studies, but its efficacy in acute settings still requires further research. Research performed on various techniques of meniscal regeneration looks promising, and regenerative medicine appears to be the way forward.”
Below I will cover research that addresses:
- Meniscus repair versus meniscus removal.
- Meniscus implants.
- Non-surgical treatments.
To have surgery or not may depend on the tear and degenerative nature of the knee
An October 2022 paper writes: (3). “Despite an abundance of literature exploring outcomes of arthroscopic partial meniscectomy for degenerative meniscus tears, there is little consensus among surgeons about the drivers of good outcomes following arthroscopic partial meniscectomy. . . . In patients with symptomatic meniscal tears, the location and tear pattern play a vital role in clinical management. Tears in the central white-white zone are less amenable to repair due to poor vascularity. Patients may be indicated for arthroscopic partial meniscectomy or non-surgical intervention depending on the tear pattern and symptoms.
Your diagnosis for meniscectomy
As we see from the research presented in this article, meniscal surgery can lead to long-term knee instability. Joints, including the knee, are able to easily move because of the gliding surface of the articular cartilage covering the ends of the bones inside the joints. The knee cartilage covers the top of the tibia and the bottom of the femur. In between these bones is the cushioning meniscus.
The meniscus or menisci are the thick, strong cartilage-like shock absorbers that cushion and pad the knee between the thigh (femur) and shin (tibia) bones. Shaped like the letter “C,” the meniscus of each knee provides stability in carrying the weight of the body on the knee and allowing the gliding of the bones through the joints full range of motion. The meniscus can become problematic either through traumatic injury, or age, and wear and tear. Wear and tear can occur in anyone, and especially in athletes, and people who have jobs that require physical activity where stresses to the knees are applied.
Meniscus injuries in sports are often caused by impact or sharp cutting or turning when the meniscus is trapped between the femur and the tibia. Typically an injury to the meniscus will occur in combination with ligament injuries, especially the MCL (Medial Collateral Ligament). One of the worst injuries to the knee is the “O’Donoghue’s Triad.” With a lateral blow to the outside of the knee (this occurs in football when a runner’s knee is impacted by a player rolling his body against the outside of the knee), the ACL (Anterior Cruciate Ligament), MCL, and the meniscus may be injured or torn at the same time. I have also seen this injury occur at dog parks when playing dogs run into their owner’s knee from the side.
Too many patients have had meniscal surgery, which is the removal of part or all of the meniscus of the knee. But why remove such a valuable piece of knee cushioning and protection? Because most physicians believe that the meniscus does not have the ability to be repaired naturally, or by surgery. So it is shaved, smoothed or removed. Years ago, when a knee was injured, the standard protocol was complete menisectomy. Many of these patients were forced to have knee replacement years later because of the severe pain from the meniscus removal, and resulting in bone on bone arthritis.
Meniscectomy: Removing meniscus tissue: Although saving the meniscus is not always easy “in the knees without the meniscus, the impact and load are three times higher.”
An October 2022 editorial (4) in the journal Arthroscopy writes: “Patients do not do as well after meniscectomy as after repair. Although saving the meniscus is not always easy and the success rate of repair is not 100%, repair-when possible-remains the best option for patients in the long run. Meniscal repair rates are on the rise, especially in younger patients, but are not high enough. Recent research has shown that more than 95% of meniscal procedures are partial meniscectomies. . . .Preserve as much meniscus as possible and as often as possible.”
A 2020 study in The archives of bone and joint surgery (5) offers an updated opinion on meniscus surgery. Here are some points brought up by the surgeon researchers.
The knee needs its meniscus:
- “The menisci (meniscus) perform many essential biomechanical functions. These functions include load transmission, shock absorption, stability, nutrition, joint lubrication, and proprioception (the sense of knee in 3D space). They also serve to decrease contact stress and increase contact area and joint congruency. The knee would be deprived of all these functions if the meniscus removed. Therefore, in the knees without the meniscus, the impact and load are three times higher.”
Surgical repair? Patients should be warned the return to sport should be delayed for up to 6 months
- “Rehabilitation after meniscal repair is slower and different from rehabilitation after meniscectomy. The physiotherapist and surgeon should respect the slow process of biological healing of the meniscus and therefore they need to be careful with the rehabilitation program especially in active flexion. The return to sport should be delayed for up to 6 months; however, 86 to 91% of patients could back to play. It is also crucial for the patient to know there is 8 to 20% risk of failure and re-operation, however, the long term outcome of meniscal repair is better than partial meniscectomy because of chondroprotective action of meniscus.”
Meniscus repair is not a small surgery without complication.
- “Meniscus repair is not a small surgery without complication. It is technically challenging and has a steep learning curve. General complications of arthroscopy such as venous thromboembolism, infection and vascular injury could occur. Specific complication including nerve injuries, ligamentous injury, iatrogenic cartilage lesions, and poor suture techniques can happen during meniscal repair. The surgeon should depict and accept the eventual complications and address them as rapidly as possible. It is also important to form patients about potential complications.”
Failure of meniscal repair occur in up to 25 % of patients
- “Failure of meniscal repair occur in up to 25 % of patients. Failures in the first six months of surgery are usually related to technical issues during repair, while failures between 6 and 24 months are indicating poor healing process. Failure later than 2 years of repair show retear or degenerative processes in the meniscus. . . Secondary meniscectomy is a treatment for failed meniscal repair. The amount of meniscal resection is less in 35% of cases, which shows partial healing of the meniscus. Revision of meniscal repair is another option and two small series reported 25 to 33% failure rate for the procedure.”
In this illustration we see the various types of meniscus repairs and meniscus tears.
In the box below we see various meniscus tear progressions:
- A small meniscus radial tear to a large meniscus radial tear which then progresses to a meniscus flap tear which then progresses to a complex or degenerative meniscus tear.
- We also see:
- A Double flap tear
- Discoid Meniscus
- Peripheral Tear
- Horizontal Flap Tear
- Displaced Flap Tear
A July 2022 study (6) reported that “the utilization of meniscal repair techniques continues to evolve in an effort to maximize the rate of healing. Meniscal repair outcomes at a minimum of 5 years postoperatively appear to better represent the true failure rates. Modern meniscal repair had an overall failure rate of 19.5% at a minimum of 5 years postoperatively. Modern all-inside techniques appear to have improved the success rate of meniscal repair compared with use of early-generation all-inside devices. Lateral repairs were significantly more likely to be successful compared with medial repairs, while no difference was seen between patients undergoing meniscal repair with and without concomitant ACL reconstruction.”
A July 2021 study (7) examined the effectiveness of arthroscopic partial meniscectomy by reviewing six previously published studies. In all six reviews of randomized controlled trials, arthroscopic partial meniscectomy did not show clinically important benefit over conservative treatment for knee function and pain. One of the studies which examined 140 middle aged patients with degenerative meniscal tears, arthroscopic partial meniscectomy provided no clinically relevant difference in Knee Injury and Osteoarthritis Outcome Score compared with a 12 week supervised exercise program.
Arthroscopic partial meniscectomy is not recommended as the first-line treatment for managing knee pain in middle age patients
I see many new patients with meniscus injury who are exploring second opinions. For some people they will be told that they will need to have surgery because the problem of their meniscus is indeed not repairable by any other means. For other who were told the meniscus surgery should be strongly considered, we can help many, not all, of these people avoid this surgery. For others their meniscus injury is not bad enough to warrant a surgery and they can be helped with injections.
A paper in the American Journal of Sports Medicine explains this further: (8)
“There is controversy about the benefit of arthroscopic partial meniscectomy for degenerative lesions in middle-aged patients.” In this study the doctors compared patient satisfaction with their arthroscopic partial meniscectomy in middle-aged patients with no or mild knee osteoarthritis and a degenerative meniscal tear and those with a traumatic (acute incident) tear. To achieve the study results, these patients were monitored for five years.
- Baseline patient characteristics were not different between groups. At the 5-year evaluation, the satisfaction rate in the traumatic and degenerative groups was 68.5% versus 71.3%, respectively. (Almost one-third or patients were dissatisfied with their surgical outcomes five years later).
- Patient satisfaction was significantly associated with functional outcomes.
- In the degenerative knee group, 37.4% had osteoarthritis progression to more advanced osteoarthritis.
- Conclusion: Who was more likely to have less than hoped for results of their arthroscopic knee surgery?
- Obese patients
- and patients with lateral meniscal tears.
- The researchers summarized who would likely be good candidates for surgery: Middle-aged patients with degenerative meniscal tears, without obvious osteoarthritis, and with failed prior physical therapy.
In most patients, a lack of benefit of surgical approach over conservative treatment
A September 2022 paper (9) assessed the functional and pain scores between exercise therapy and arthroscopic surgery for degenerative meniscal lesions. The authors here noted: “Arthroscopic partial meniscectomy (APM) is widely applied for the treatment of degenerative meniscal lesions in middle-aged patients; however, such injury is often associated with mild or moderate osteoarthritis and has been reported by MRI in asymptomatic knees. Previous studies suggested, in most patients, a lack of benefit of surgical approach over conservative treatment, yet many controversies remain in clinical practice. . . Conservative treatment based on physical therapy should be the first-line management. However, most systematic reviews revealed subgroups of patients that fail to improve after conservative treatment and find relief when undergoing surgery.”
A January 2022 study (10) suggested that while degenerative meniscal lesions typically occur in middle-aged or elderly patients without any history of significant acute trauma, its prevalence does increase with age and are associated and can cause or be caused by knee osteoarthritis. “The most frequent orthopaedic treatment is arthroscopic partial meniscectomy (APM) to relieve pain and functional deficit associated with degenerative meniscal lesions. Nevertheless, several randomized controlled clinical trials recommend against arthroscopic partial meniscectomy as the first-line treatment for managing knee pain in patients affected by degenerative meniscal lesions and no radiographic knee knee osteoarthritis that should be reserved for cases of failure after 3 month conservative therapy or earlier in patients with significant knee mechanical symptoms.”
A January 2023 systematic review and meta-analysis study (11) examined data from previously published studies on arthroscopic partial meniscectomy versus non-surgical or sham treatment in patients with MRI-confirmed degenerative meniscus tears. The patients in these previously published studies averaged about 55 years old with 52% being women. The researchers primary outcomes were knee pain, overall knee function, and health-related quality of life, at 24 months follow-up.
Results: The arthroscopic partial meniscectomy group showed a small improvement over the non-surgical or sham group on knee pain at 24 months follow-up. However overall knee function and health-related quality of life did not differ between the two groups. They did not find a relevant subgroup of patients who benefitted more from the arthroscopic partial meniscectomy than the sham surgery.
But arthroscopic partial meniscectomy should not be discouraged completely in older patients
In August 2022, doctors published findings (12) on the the effect of the patient’s age on knee survivorship after arthroscopic partial meniscectomy for degenerative medial meniscus tears. The study population including data on 633 knees were divided into older and younger groups, the cutoff age was 60 years old. A significant difference in the joint survival rates was noted between the groups. The doctors found knee survivorship after arthroscopic partial meniscectomy was affected by other factors associated with the aging process, such as cartilage status and meniscal tear pattern, rather than age itself. They write: “Advanced age should not be the only reason for precluding arthroscopic partial meniscectomy in treatment of degenerative medial meniscus tears. Arthroscopic partial meniscectomy is a viable option when treating degenerative medial meniscus tear in elderly patients if adopted with caution.” In other words the right candidate for treatment.
Arthroscopic partial meniscectomy no better than exercise
An August 2022 paper (13) compared the effectiveness of exercise versus arthroscopic partial meniscectomy and further against an exercise for degenerative meniscal tears program in knee function at 5-year follow-up. The researchers of this study compiled data from four previously published studies. The data revealed that there was no significant differences in activities of daily living and quality of life in the study groups. The study concluded: “Moderate certainty of evidence suggests that the addition of arthroscopic partial meniscectomy to an exercise program adds no benefits in knee function at 5-year follow-up.”
A July 2022 study (14) also found “no evidence in support of arthroscopic partial meniscectomy in adults with degenerative and nonobstructive meniscal symptoms.” The researchers of this study tackled the problem of understanding the benefits of arthroscopic partial meniscectomy versus exercise. They write: “It is unclear whether the results of arthroscopic partial meniscectomy (APM) are comparable to a structured physical therapy (PT).”
In a review of data from 17 studies (2037 patients). the researchers found that current evidence suggests no difference in functional and clinical patient reported outcomes, pain, quality of life, physical performance measures, and osteoarthritis progression between the arthroscopic partial meniscectomy and structured physical therapy groups.
A July 2022 study (15) compared arthroscopic partial meniscectomy or exercise therapy outcomes in meniscus tear patients five years after treatments. The researchers found that exercise-based physical therapy worked as well as arthroscopic partial meniscectomy for patient-reported knee function. The authors recommended: “Physical therapy should therefore be the preferred treatment over surgery for degenerative meniscal tears. These results can assist in the development and updating of current guideline recommendations about treatment for patients with a degenerative meniscal tear.”
Meniscus transplant surgery – “Meniscal allograft transplantation for symptomatic knees after meniscectomy decreases pain and often improves function, but it does not replicate a normal meniscus”
Sometimes I will get an email or phone call asking me about meniscus transplants. The person who asks me has been told that they have a bone on bone situation in their knee. What I find interesting is that many of these people are active people. They maybe having a little trouble running or jogging but they can ride their bicycles without issue, they are even skiing, and they can walk okay. So this is a knee that is functioning and moving. But, the person who contacts me says that they have be recommended to a meniscus transplant because they have “bone on bone and the meniscus transplant will bring back some cushion.”
Meniscal transplant is a very major surgery.
In addressing how to clinically address the problem of missing meniscus tissue in patients, researchers writing (16) in November 2021 discussed the challenges of long-term understanding of the treatment options: “Meniscus tissue deficiency resulting from primary meniscectomy or meniscectomy after failed repair is a clinical challenge because the meniscus has little to no capacity for regeneration. Loss of meniscus tissue has been associated with early-onset knee osteoarthritis due to an increase in joint contact pressures in meniscectomized knees. Clinically available replacement strategies range from allograft transplantation to synthetic implants, including the collagen meniscus implant, ACTIfit, and NUSurface (NUSurface . Although short-term efficacy has been demonstrated with some of these treatments, factors such as long-term durability, chondroprotective efficacy, and return to sport activities in young patients remain unpredictable. Investigations of cell-based and tissue-engineered strategies to treat meniscus tissue deficiency are ongoing.” Once a meniscus is removed or partially removed, it is very difficult to replace it.
In December 2020, there was an editorial in the medical journal Arthroscopy (17). It gives a good reality of the meniscus transplant outcome.
“Meniscal allograft transplantation for symptomatic knees after meniscectomy decreases pain and often improves function, but it does not replicate a normal meniscus. The ability of to delay arthritic changes is an ongoing area of study, and it is known that outcomes and graft survivorship deteriorate with longer follow-up. Recommended indications are symptomatic patients after meniscectomy with mild (or at most moderate) degenerative changes and absence of (or surgically corrected) associated malalignment or ligament deficiency. When these indications are followed, 80% of patients improve, with survivorship of 83% at 10 years and 56.2% at 20 years.
A September 2021 paper writes: (18) Meniscal allograft transplantation provides treatment options for patients with a meniscus-deficient knee with lifestyle-limiting symptoms in the absence of advanced degenerative changes. Meniscal transplantation helps to restore the native biomechanics of the involved knee, which may provide chondroprotective effects and restoring additional knee stability. Improvements in pain, function, and activity level have been seen in appropriately selected patients undergoing transplantation. . . Although meniscal transplantation may serve as a salvage procedure for symptomatic patients with a meniscus-deficient knee, it may prevent or delay the necessity of a more invasive arthroplasty (knee replacement) procedure.”
Meniscal allograft transplantation
- Meniscal allograft transplantation is a surgery in which a meniscus from a cadaver is used to replace your meniscus.
Doctors in South Korea have published findings in which they suggest that clinical outcomes after meniscal allograft transplantation in arthritic knees are unclear. Further, the procedure is not recommended to patients with osteoarthritic bone changes because the doctors found that the procedure is not effective if there is already bone damage.(19)
In November 2017 doctors published even more troubling research in the American Journal of Sports Medicine.(20)
“When comparing a patient series with full-thickness chondral defects who underwent Meniscal allograft transplantation with a patient series with NO chondral defects, there were no differences in the change in individual patient outcomes from preoperative to the final follow-up.
Similarly, there were no differences in complications or failure between those with NO chondral defects or full-thickness chondral defects diagnosed intraoperatively.
The results of the current study suggest that chondral damage identified and treated by cartilage restoration (repaired full thickness cartilage) at the time of Meniscal allograft transplantation may not affect the clinical outcomes of Meniscal allograft transplantation.” The paper notes that those with repaired full thickness cartilage and Meniscal allograft transplantation, had the same rate of need for secondary surgery and complete failure leading to knee replacement.
A December 2021 study (21) provided yet another update:
“While the refined implementation of Meniscal allograft transplantation has shown promising results in patients and athletes, it still has several limitations including extrusion and shrinkage of the graft. The success rate for the two major scaffolds (i.e., collagen scaffolds, polyurethane scaffolds) varies from 38% to as low as 0% after 4 years of follow-up. The long-term results of scaffolds and allografts can be unpredictable, and it is documented that some may become non-functional due to shrinkage, extrusion, and fragmentation. Taken together, these findings highlight the importance of long-term follow-up studies to inspect not only the health of the meniscus but also the entire knee in order to adequately determine the success of any treatment.”
A September 2022 paper (22) had doctors in New York state assessing the medical records of patients under going arthroscopic meniscus surgery. They noted: “Meniscal allograft transplantation, though relatively uncommon, is being performed with greater frequency in New York state. Surgeons should counsel patients regarding the likelihood of requiring subsequent knee surgery after Meniscal allograft transplantation, with repeat arthroscopic partial meniscectomy being the most commonly performed procedure.”
Doctors found successful outcomes in 65% of the operated knees they examined post cartilage – meniscus transplant surgery.
In a recent study from Harvard, (23) doctors found successful outcomes in 65% of the operated knees they examined post cartilage – meniscus transplant surgery. These surgical procedures, the study suggests, can allow patients to retain their biological knees, delay or prevent rapid degeneration to osteoarthritis, and could be recognized as a bridge procedure before artificial knee replacement. (A stop gap measure to delay knee replacement). The researchers noted a 35% failure rate.
“Surgeons should be aware of the low likelihood of return to military duty at more than 2 years after Meniscal allograft transplantation”
In April 2020, (24) army researchers examined soldier’s ability to return to active duty following meniscal allograft transplantation. These are their results:
“Meniscal allograft transplantation is considered a viable surgical treatment option in the symptomatic, post-meniscectomy knee and as a concomitant procedure with ACL revision and articular cartilage repair. “
While these surgeons noted that promising outcomes have recently been reported in active and athletic populations, Meniscal allograft transplantation has its limits, especially in a high-demand military population. In fact the results suggest that many army personnel cannot return to active duty. This is what they wrote:
“Surgeons should be aware of the low likelihood of return to military duty at more than 2 years after Meniscal allograft transplantation and counsel patients accordingly. Based on this study, Meniscal allograft transplantation does not appear to be compatible with continued unrestricted military duty for most patients.”
The Meniscal allograft transplantation surgery is considered successful even if you do not return to sports
A March 2020 study (25) suggested:
“Meniscal allograft transplantation may improve symptoms and function, and may limit premature knee degeneration in patients with symptomatic meniscal loss. The aim of this retrospective study was to examine patient outcomes after Meniscal allograft transplantation and to explore the different potential definitions of ‘success’ and ‘failure’.
- Forty-three patients who underwent Meniscal allograft transplantation were asked if they considered the surgery a success or failure and were they able to return to sports.
- Surgical failure was considered if: (removal of most/all the graft had to be done, revision Meniscal allograft transplantation or conversion to knee replacement had to be performed), pain relief was not achieved, complication rates (surgical failure plus repeat arthroscopy for secondary allograft tears). Patients were also asked if they would have the procedure again.
- The complication rate was 9% surgical failures and 21% were clinical failures. Half of those patients considered a failure stated they would undergo Meniscal allograft transplantation again because it achieved some pain relief.
- Inability to return to sport is not associated with failure since 73% of these patients would undergo Meniscal allograft transplantation again.
“Despite that most studies reported high return to sports rate, the current level of evidence is low with all studies being case series.”
This research was followed up by a November 2021 study (26) which came to similar conclusions:
“A total of 14 case series were included with 670 patients. . . The return to sports rate ranged from 20%-91.7%, with two studies reporting low return to sport rates. The return to sport time ranged between 7.6-16.9 months. The return to pre-injury level with a rate of 7-100%. Return to a higher level of sports was only reported in two studies (28.5%-86%). Return to a lower level of sports was reported low proportions in most studies. . . The total reoperation rate following MAT ranged between 3.1%-80%, whereas the total failure ranged between 1.1-30.1%.
Conclusion: Despite that most studies reported high return to sports rate, the current level of evidence is low with all studies being case series. There is significant variability in the reported return to sports rate, time, and level. Therefore, high-quality comparative studies are mandated to elucidate whether MAT is associated with higher return to sports rates and levels.”
A November 2022 study (27) compared a partial meniscectomy procedure and meniscal suture repair in elite athletes with an isolated meniscal injury. What the researchers found was similar results. Partial meniscectomy and meniscal suture showed similar rates of return to sport and return to pre-injury levels. Partial meniscectomy also got the athlete back to the sport faster. The study found “athletes required more time for return to sport after meniscal repair and exhibited an increased rate of revision surgery associated with a reduced rate of return to sport after the subsequent surgery. For lateral meniscus tears, meniscectomy was associated with a high rate of revision surgery and risk of chondrolysis, whereas partial medial meniscectomy allowed for rapid return to sport but with the potential risk of developing knee osteoarthritis over the years.”
Synthetic meniscal implants
A June 2022 paper (28) assessed failure rates and clinical outcomes of synthetic meniscal implants following partial meniscectomy. Meniscal (tissue replacement) substitution with scaffolds may be advantageous following partial meniscal resection. . . However, “the evidence for meniscal scaffold use is insufficient to suggest that they could potentially improve clinical outcomes in patients post-meniscal resection. This is largely due to the high proportion of concurrent procedures performed at index procedure . . . On the basis of current evidence, the use of meniscal scaffolds as a sole treatment for partial meniscal defects cannot be recommended, owing to the relatively high failure rate and paucity of clinical data.”
An April 2021 paper (29) In this randomized controlled trial involving subjects with knee pain following partial meniscectomy, the researchers hypothesized that treatment with a synthetic medial meniscus replacement implant provides significantly greater improvements in knee pain and function compared to non-surgical care alone. In this prospective, multicenter randomized controlled trial , subjects with persistent knee pain following one or more previous partial meniscectomies were randomized to receive either medial meniscus replacement or non-surgical care. Treated subjects had an average age of 52 years old and one or more previous partial meniscectomies at an average of 34 months. Treatment with the synthetic MMR implant resulted in significantly greater improvements in knee pain, function, and quality of life at 1 year of follow-up compared to treatment with non-surgical care alone.
A September 2021 paper (30) Meniscal allograft transplantation provides treatment options for patients with a meniscus-deficient knee with lifestyle-limiting symptoms in the absence of advanced degenerative changes. Meniscal transplantation helps to restore the native biomechanics of the involved knee, which may provide chondroprotective effects and restoring additional knee stability. Improvements in pain, function, and activity level have been seen in appropriately selected patients undergoing transplantation. . . Although meniscal transplantation may serve as a salvage procedure for symptomatic patients with a meniscus-deficient knee, it may prevent or delay the necessity of a more invasive arthroplasty procedure.
A June 2022 paper (31) aimed to assess the impact of biodegradable polyurethane meniscus scaffold implantation on muscle strength and balance in comparison with the healthy contralateral knee in patients with irreparable medial meniscus defect. BPMSI led to decreased pain and improved function at postoperative week 36. Although muscle strength almost returned to normal, balance parameters did not recover within 36 weeks after the procedure.
What about athletes and their ability to return to sport after surgery
When surgery removes too much meniscus
People may have significant knee pain after meniscus surgery because too much meniscus removed. This problem is described in a September 2021 paper presented in the Sports medicine and arthroscopy review.(32)
“Certain (meniscus tear injuries) are often treated with arthroscopic partial meniscectomy, which can effectively relieve symptoms. However, removal of meniscal tissue can also diminish the ability of the meniscus to dissipate hoop stresses (weight bearing pressure on the outside of the meniscus), resulting in altered biomechanics of the knee joint including increased contact pressures.”
“Altered biomechanics of the knee joint including increased contact pressures” describes a situation of accelerated knee osteoarthritis. This can be where the more pain after surgery is coming from. What may occur is that the surgery removed a portion of the meniscus to alleviate the patients pain. In doing so, the surgery made the meniscus smaller in size and compromised and weakened the meniscus’ ability to provide the needed cushion Nature designed it for.
The patient with many meniscus surgeries and a prognosis of eventual knee replacement
Removing tissue from your knee can only make your knee weaker in the long run and prone to arthritis. This is why many have numerous surgeries on their knees, trying to correct problems in part caused by tissue removal. Removal of the meniscus (or knee cartilage) decreases the shock absorption that protects the knee. Why shave it then? Because some physicians believe that the meniscus does not have the ability to be repaired, either by regular body repair mechanisms or surgery. So it is shaved, smoothed, or partially removed. Years ago, when a meniscus was injured, the standard protocol was complete removal and resultant bone‑on‑bone arthritis in the future. Many of these poor patients were forced to have knee replacements years later because of the severe pain from the meniscus removal.
Like many in our field, we see patients who have had numerous arthroscopic surgeries. Sometimes these patients even brag about how many surgeries they had. Most will stop bragging once they learn that they will ultimately need a knee replacement and that the activities or work they did/do that accelerated their meniscus problems will most likely come to an end because the knee replacement will not allow them the range of motion needed to continue on.
For the patient who has had numerous surgeries, eventually many will report that the last surgery left nothing remaining to repair. A meniscectomy was performed and now the “count down” had begun to knee replacement. I will stop here to answer the question that we are asked the most. Is there any treatment that will regrow meniscus tissue. The answer is yes, however, the reality of the situation is that these treatments, namely orthobiologics such as platelet rich plasma and stem cell therapy cannot grow a meniscus from nothing. They can help however repair a damaged meniscus. These treatments are explained below along with other conservative care treatments. Many people have also asked us about biological 3D cellular printing of a new meniscus. This technology while promising and exciting is many, many years away.
The knee needs its meniscus:
A summary of the role of the meniscus is given in a June 2021 paper (33) exploring the use of Platelet rich Plasma injections after meniscus surgery and whether the injections facilitated a faster healing. I will discuss that further below.
“The meniscus plays an important role in the knee joint, as it plays a role in shock absorption and transmission, joint stabilization, proprioception, lubrication and nutrition of the articular cartilage. Biomechanical studies have shown that a loss of meniscal integrity leads to changes in kinematics and loading of the knee joint. Even a loss of only 15–34% of the meniscus tissue increases the load on the hyaline cartilage by up to 350%.”
In this image we are looking down at the top of the knee and seeing what sits on top of the shin bone. On this knee’s right side is the medical collateral ligament next to the medical meniscus. To this knee’s left is the lateral meniscus and next to it is the lateral collateral ligament. We also see the red and white zones.
The Meniscus is always trying to make more meniscus
In a recent study, doctors noted: “The repair of meniscus tissue in the avascular zone (the White Zone) remains a great challenge, largely owing to their limited healing capacity (Or the lack of blood supply, that is why the zone is white).” The researchers continued: ” A comprehensive review of the literature suggests that MSCs possess an intrinsic therapeutic potential that can directly and indirectly contribute to meniscus healing.”(34)
If you had a meniscus tear you are familiar with “White Zone,” and “Red Zone,” meniscus tears. The “Red Zone,” part of the meniscus, the outer edges, receives a steady stream of healing cells from its well organized blood vessel network. For those of you with a meniscus injury that is being recommended to surgery, you may have had your doctor explain to you that you have a “White Zone,” tear. The “White Zone,” lies in the center of the meniscus. It does not have a well organized blood network. It is these meniscal injuries that send patients to surgery.
This is what these researchers said: “studies revealed that migrating cells were mainly confined to the red zone in normal menisci: (This is the area where the meniscus has good blood flow and healing elements are abundant). However, these cells were capable of repopulating defects made in the white zone, (the area without circulation). When the meniscus was injured, migrating cell numbers increased dramatically. Stem cells in the knee increased in number to combat the injury. These findings demonstrate that, much as in articular cartilage, injuries to the meniscus mobilize an intrinsic progenitor cell population with strong reparative potential, even into the white zone area.”
A study published in the journal Arthroscopy (35) also suggested: “The existence of progenitors (stem cells) and presence of microvasculature in the (white) zone of the meniscus suggests the potential for repair and biologic augmentation strategies in that zone of the meniscus in young healthy adults.
What some may find fascinating is that the meniscus signals for more stem cells from the knee capsule to come to the injured area. For those people asking about stem cell numbers that are harvested for treatment, the meniscus is mobilizing the stem cells already in the knee to the site of the its injury.
The meniscus and cartilage are always trying to heal each other
An October 2020 paper titled: “The menisci and articular cartilage: a life-long fascination,” (36) explains that the “menisci and articular cartilage of the knee have a close embryological, anatomical and functional relationship, which explains why often a pathology of one also affects the other.”
In the Journal of orthopaedic research (37) doctors examined the process of meniscal regeneration and cartilage degeneration following meniscus surgical removal in mice. They found that there is a healing environment that the meniscus and cartilage create independently of each other spurred on by native stem cells, that later melds together, suggestive of a balance between meniscal regeneration and cartilage homeostasis. The meniscus and cartilage are trying to regenerate each other.
This special relationship between cartilage, meniscus and stem cells is discussed in research from the University of Iowa. The Iowa findings demonstrate that, much as in articular cartilage, injuries to the meniscus mobilize an intrinsic progenitor (stem cell) population with strong reparative potential.(38) The problem for patients is that despite the desire to heal and regenerate, as pointed out by the Iowa researchers, “Serious meniscus injuries seldom heal and increase the risk for knee osteoarthritis; thus, there is a need to develop new reparative therapies. In that regard, stimulating tissue regeneration by autologous stem/progenitor cells has emerged as a promising new strategy.”
The meniscus and cortisone: Cortisone injections before meniscus surgery are there risks?
A November 2022 paper (39) Writes: “Consensus guidelines recommend administering a corticosteroid injection (CSI) for patients with a symptomatic degenerative meniscus lesion prior to arthroscopic partial meniscectomy. A recent study found that corticosteroid injection administered within 1 month prior to meniscectomy is associated with an increased risk of postoperative infection. However, infections may range in severity from superficial infections to serious infections requiring surgical interventions. Serious infections requiring a surgical intervention are rare after a meniscectomy, occurring in 0.1% of APMs in a matched cohort of patients over 35. Patients were five times more likely to return to the operating room for infection after APM if they had a corticosteroid injection in the month before or had multiple corticosteroid injection in the year before surgery. The risk of infection was no longer significant if there was at least a 2-month interval between preoperative corticosteroid injection and arthroscopic partial meniscectomy.”
A May 2022 report (40) evaluated the risk of post-operative infection after intra-articular steroid injection at the time of knee arthroscopy. The patients in this study were included if they underwent more simple arthroscopic procedures: diagnostic arthroscopy, meniscectomy, loose body removal, synovectomy, or microfracture. Patients were excluded if they underwent more complex procedures, such as ligament reconstruction, meniscus repair, or any open procedures.
A total of 6889 patients were identified for study inclusion, including 2416 (35.1%) who were given intra-articular steroid at the time of knee arthroscopy.
Conclusions: “Knee infection following arthroscopic surgery is rare. Intra-operative steroid injection during arthroscopic knee surgery is associated with a 4.3-fold increased risk of subsequent knee infection. While the overall risk remains low, the use of intra-operative steroids is expected to result in one additional knee infection for every 448 arthroscopic procedures performed.
Why regenerative medicine injections? For some it is because of numerous failed meniscus surgeries. For others the reality of meniscus surgery can mean advanced knee osteoarthritis.
Is surgery the only option? What is the future of meniscus repair treatments? According to a March 2021 study (41) the future of meniscus repair treatments is not only surgery. It is suggested that that orthobiologics (PRP and stem cell applications) should play an important role in meniscus repair.
- 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 the injured area to stimulate healing and regeneration. Please see our article: What is PRP, Platelet Rich Plasma therapy?
- Bone marrow aspirate concentrate injections or stem cell therapy: Bone marrow stem cell therapy is the injection, into a damaged joint and surrounding area, of stem cells drawn from the patient’s own bone marrow. Please see our article: Bone marrow aspirate concentrate injections
This study was the cumulative result of an electronic survey including 10 questions sent in a blind fashion to the faculty members of the 5th International Conference on Meniscus Science and Surgery. The responders of this study suggested that the future of meniscus science should be focused on meniscal preservation techniques through meniscus repair, addressing meniscal extrusion, and the use of orthobiologics.
Someone will write us that they suffered a bucket handle meniscus tear and attempted to repair it. They will write about two or even three or meniscus surgeries that failed and then a subsequent total meniscectomy after they continued to try to “play through the meniscus problem.”
Others write that they have put off meniscus surgery for various reasons, Eventually their meniscus injury has become much worse and even though their pain has increased they are still looking for options to knee arthroscopic surgery.
Others have been given the ultimatum that not only do they need knee surgery now, they need total knee replacement because their meniscus is shredded, their knee is now bone-on-bone, and there are no other options left.
PRP, bone marrow and adipose tissue in meniscus and ligament repair
A June 2021 paper (42) discusses the possibility of meniscus regeneration with PRP and bone marrow and adipose tissue sell injections. This is a case history.
“Conventional pharmacological and surgical treatments are effective in treating the condition; however, do not result in regeneration of healthy tissues. In this report, we highlight the role of cell-based therapy in the management of medial and lateral meniscal and anterior cruciate ligament tears in a patient who was unwilling to undergo surgical treatment. We injected autologous mesenchymal stem cells obtained from the bone marrow and adipose tissue and platelet-rich plasma into the joint of the patient at the area of injury, as well as intravenously. The results of our study corroborate with those previously reported in the literature regarding the improvement in clinical parameters and regeneration of meniscal tissue and ligament. Thus, based on previous literature and improvements noticed in our patient, cell-based therapy can be considered a safe and effective therapeutic modality in the treatment of meniscal tears and cruciate ligament injury.”
I want to point out that we do not offer intravenous stem cell therapy. This decision is based on more than 25 years of regenerative medicine experience.
Can stem cells help your meniscus related knee problems?
A March 2021 study (43) gave this assessment in a paper titled: “Cell-based treatment options facilitate regeneration of cartilage, ligaments and meniscus in demanding conditions of the knee by a whole joint approach.”
“Overall, cell-based regenerative cartilage therapy of the knee has shown tremendous development over the last years and has become the standard of care for large and isolated chondral defects. It has shown success in the treatment of traumatic, osteochondral defects but also for degenerative cartilage lesions in the demanding condition of early osteoarthritis. Future developments and alternative cell sources may help to facilitate cell-based regenerative treatment for all different structures around the knee by a whole joint approach.”
Researchers at the Osaka University Graduate School of Medicine in Japan teamed with the Mayo Clinic to release a January 2020 (44) paper outlining the current research on stem cell therapy for meniscus repair. In this study they wrote:
“Clinical studies evaluating the effects of MSC (stem cell) injections in the knee joint are limited, but early clinical data suggests encouraging results. Currently, there have not been any reported safety concerns or side-effects in the clinical use of MSC injections.
Randomized double-blind controlled studes to date studying the effects of MSC injections into the knee post medial meniscectomy are rare. A 2014 study (45) contained 55 subjects in 3 groups who underwent a percutaneous injection of allogeneic MSCs with one group receiving 50 × 106 cells another 150 × 106 cells and control receiving only hyaluronic acid. At 12 months follow up, MRI scan findings reported a significant increase in meniscal volume in 24% of patients receiving 50 × 106 cells and 6% receiving 150 × 106 cells. None of the control group patients demonstrated an increase in meniscal volume. The study is limited to MRI scan being the only objective outcome measure, but the study methodology is rigorous in that it has the advantage of being blinded and randomized.”
In December 2021, doctors published a summary understanding of using stem cells in meniscus repair, based on the current research of stem cell repair of a meniscus tear. (46) According to the study authors:
“Due to the special anatomical features of the meniscus, conservative or surgical treatment can hardly achieve complete physiological and histological repair. As a new method, stem cells promote meniscus regeneration in preclinical research and human preliminary research. We expect that, in the near future, in vivo injection of stem cells to promote meniscus repair can be used as a new treatment model in clinical treatment.”
“The treatment of animal meniscus injury, and the clinical trial of human meniscus injury has begun preliminary exploration. As for the animal experiments, most models of meniscus injury are too simple, which can hardly simulate the complexity of actual meniscal tears, and since the follow-up often lasts for only 4-12 weeks, long-term results could not be observed. Lastly, animal models failed to simulate the actual stress environment faced by the meniscus, so it needs to be further studied if regenerated meniscus has similar anti-stress or anti-twist features.”
“Despite these limitations, repair of the meniscus by MSCs has great potential in clinics. MSCs can differentiate into fibrous chondrocytes, which can possibly repair the meniscus and provide a new strategy for repairing meniscus injury.”
Can meniscus tissue be regrown?
For many people, the long rehabilitation, possible need for secondary surgery, and other post-surgical factors weigh heavily in their decision making process as to how to proceed to fix their meniscus tear. For many people, regenerative medicine in the form of bone marrow aspirate concentration stem cells may be something to be explored.
Let’s look at an October 2020 study (47) that made some interesting observations. What the research team wanted to do was assess Bone marrow-derived mesenchymal stem cells’ potential to engineer meniscus-like tissue. The researchers pointed out that “Bone marrow-derived mesenchymal stem cells have the potential to form the mechanically responsive matrices of joint tissues, including the menisci of the knee joint.” So to test how good these stem cells were at re-engineering meniscus tissue, they compared the bone marrow stem cells taken from the iliac crest versus the meniscus fibrochondrocytes cells (cartilage cells) isolated from castoffs of partial meniscectomy from non-osteoarthritic knees.
To simulate conditions that may occur in the human body after cell transplantation, the bone marrow-derived mesenchymal stem cells were cultured in type I collagen (the stuff that cartilage is made of) scaffolds. What they found was that the bone marrow-derived mesenchymal stem cells produced functional replacement meniscus tissue better than meniscus tissue did. This study is not definitive in the way bone marrow derived stem cells may heal and regenerate meniscus tissue. What it does show however is what could be possible in the right setting.
Does PRP help during surgery?
Many patients have found success with PRP treatments during the meniscus procedure. An October 2022 study however outlines this: (48) “Although meniscus repairs augmented with PRP led to significantly lower failure rates and better postoperative pain control compared with those of the non-PRP group, there is insufficient random control study evidence to support PRP augmentation of meniscus repair improving functional outcomes.”
PRP injections after meniscus surgery
I am going to return to the study (33) I mentioned above assessing if PRP injections would facilitate healing after a meniscus repair surgery. The authors of this research say:
“Vascularization and nutritional status of the injured meniscus area, as well as the type of meniscus tear, are important indicators for the success of meniscus reconstruction. The inner 2/3 of the meniscus (“white-white”) is nourished by diffusion of factors from the synovial fluid, while the peripheral “red-red zone” has a vascular supply. Between the white-white zone and the red-red zone is a red-white transition zone.
Due to its avascular nature, meniscal healing is a critical issue after injury. In the primary meniscal repair setting, some studies regarding isolated (meniscus) repair in ligament-stable knees observed variable clinical healing or success rates ranging between 33% and 76%. (This means the success was not achieved in 67% and 24% of patients in this range of studies). As many researchers suggest, concomitant ACL reconstruction surgery may improve the healing rates of a repaired meniscus compared to isolated repair. Research has focused on promoting healing with external stimulants, such as fibrin clots, fibrin glue, synovial grafts, periosteum and mesenchymal stem cells. PRP has been widely used in sports medicine with a variety of properties and applied methods.”
In this study, PRP injections were given to people after meniscus surgery and the results were compared to people who had meniscus surgery and no PRP injections. The researchers did not see any real difference. One reason the researchers speculated was PRP was not randomly assigned. The patients who received the PRP was decided on by the surgeon who may have had more extensive damage and who the researchers believed were not good candidates for PRP as “the healing potential in this group was lower.” They also noted on the positive that despite this, “the functional result and failure rate showed a trend that was better than that of the non-PRP group. “
With over 25 years experience in regenerative medicine techniques and the treatment of thousands of patients, Dr. Darrow is considered a leading pioneer in the non-surgical treatment of degenerative Musculoskeletal Disorders and sports related injuries. He is one of the busiest Regenerative Medicine doctors in the world. Dr. Darrow has co-authored and continues to co-author leading edge medical research including research on bone marrow derived stem cells. He also comments and writes on research surrounding the treatment of chronic tendon injury, ankle and foot pain, elbow, hand and finger pain.
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