Patellar Instability and Dislocation

Patella instability is one of the more common problems we see. Many knees we see are unstable, not because of one single issue, but because of a number of combined degenerative knee situations.

Your knee cap or patella is held in place by tendons that allow it to move and slide within the trochlear groove and the base of the thigh bone. The patella moves as you bend your knee and straighten your knee. Your knee problems may have began with a kneecap sliding outside its groove or it may have begun with a knee impact injury that pushed your patella out of its groove. This can be the result of an obvious and traumatic impact injury or degenerative wear and tear to the quadriceps tendon and the medial patellofemoral ligament (MPFL), patellomeniscal ligament, patellotibial ligament, and retinaculum, the major connective tissue that hold the knee cap in place. In degenerative conditions and post-traumatic injury pain, functional issues, and eventually osteoarthritis will develop. The knee cap or patella dislocations is a common injury mostly seen in younger athletes, especially in the female adolescent athlete. It is also an injury that can often reoccur and why surgery may be recommended.

What are the treatment options for chronic patella dislocation?

If you had an impact injury or degenerative wear and tear on your knee has caused chronic patella “mal-tracking” of an inverted “J” path floating patella that is moving outside the natural groove a number of treatments may have already been prescribed for you. These include:

  • Physical therapy with the goal of strengthening the quadriceps muscle to help pull the patella back into the groove and keep it there. Some may suggest hip exercises particularly the hip abductors and flexors that help the knee maintain its shape.
  • Knee braces or various types of compression sleeves and taping may help externally keep the patella in place but this is literally a “band-aid” approach and is not considered a long-term solution.
  • Bracing – Taping, or the use of a brace on the patella, can assist in some cases, however it is not a long-term solution.
  • Various footwear solutions to keep pressure off the knee cap.

Most patella dislocations will be treated with conservative care options. In case where the dislocations caused fragments of cartilage or extensive cartilage damage, surgery may be explored because of high recurrence rates. However surgery may not be the answer for all.

Guidelines published in the medical publication STATPEARLS (1) says it this way:

“The mainstay of treatment for first-time dislocators without evidence of loose bodies or intra-articular damage is conservative, including analgesia, icing and NSAIDs to reduce pain and swelling, physiotherapy and activity modification. Bracing in a J brace or a patella stabilizing sleeve may be beneficial short term (2 to 4 weeks) to allow the soft tissues to heal. Subsequent, physiotherapy should be started with an emphasis on quadriceps and vastus medialis oblique strengthening, core strengthening and proprioception. The patient can be allowed to weight bear as tolerated.”

Hypermobile Ehlers-Danlos Syndrome (hEDS)

Another cause we see in patients is the diagnosis of Hypermobile Ehlers-Danlos Syndrome (hEDS). A disease where the ligaments of the body are in state of laxity or looseness. Patients with hEDS may experience frequent dislocations and an ability to put the knee cap back in place by themselves.

Chronic patella dislocation


A February 2022 paper (2) looked to understand how to better predict the risk of patella dislocation recurrence following a first lateral patellar dislocation. The study team looked at patients with first lateral patellar dislocation and a minimum two-year follow-up after nonoperative conservative care treatment.

  • In total, 115 of 201 patients (57%) experienced recurrent lateral patellar dislocation within 2 years after the initial lateral patellar dislocation. Patients younger than sixteen at primary lateral patellar dislocation, history of contralateral instability, and trochlear dysplasia (a flattened knee groove that the patella sits in) were significant risk factors for recurrent lateral patellar dislocation. The prediction accuracy including these 3 risk factors was 79%. Conclusion: Young age and trochlear dysplasia are major risk factors for early recurrent lateral patellar dislocation.

The damage of the impact injury goes beyond a dislocated patella

The problem of chronic dislocation is more than a problem of the knee cap floating out of place. It is a problem of the whole knee, described in this way in an August 2021 paper published in Musculoskeletal disorders. (3)

“After first-time patellar dislocation, the dynamic position of the femur in relation to the tibia plays an important role in joint stability, because the medial stabilizer of the patella (mostly the Medial Patellofemeral Ligament) is damaged or inefficient. The most important factor in controlling the rotational movement of the tibia in relation to the thigh are the hamstring muscles.”

The researchers then determined whether patients with patellar instability have a significant weakness in the knee flexor muscles, which can predispose to recurrent dislocations. This, they say,  “is an important consideration when planning the rehabilitation of patients with first-time patellar dislocation.”

  • “In patients with recurrent patellar dislocation, knee flexors strength is decreased significantly in both the unaffected and affected limbs. This may indicate a constitutional weakening of these muscles which can predispose to recurrent dislocations.”

Gait abnormalities in patella instability

An August 2022 paper (4) looked for ways to identify  potential gait deviations in patellofemoral instability to help with the development of effective rehabilitation strategies. What the study found is that it may be difficult  to determine. “Subjects with patellofemoral instability show decreased walking speed, stride length, and cadence. Some studies reported changes not only in knee kinematics and kinetics but also in hip and ankle kinematics and kinetics. There is evidence that most subjects with patellofemoral instability walk with a quadriceps avoidance gait and show increased genu valgum posture, but there is still great variability in the coping responses within individuals with patellofemoral instability. The discrepancy among the study results might underpin the fact that patellofemoral instability is a multifactorial problem, and subjects cope with the different underlying morphological as well as functional deficits using a variety of gait strategies, which makes the interpretation and understanding of the gait of subjects with patellofemoral instability a clinically challenging task. ”

Research on exercise therapy with more reps and lighter resistance – Blood Flow Restriction Therapy for Patella Instability

A January 2022 paper (5) assessed the effectiveness of blood-flow restriction training for patellar instability. The researchers hypothesized that this strategy would improve patient-reported outcomes and accelerate restoration of symmetric strength and knee biomechanics necessary to safely return to activity. They write: “Patellar instability is a common and understudied condition that disproportionally affects athletes and military personnel. The rate of post-traumatic osteoarthritis that develops following a patellar dislocation can be up to 50% of individuals 5-15 years after injury. Conservative treatment is the standard of care for patellar instability however, there are no evidence-informed rehabilitation guidelines in the scientific literature. . .  The current standard of care for non-operative treatment of patellar instability is highly variable does not adequately address the mechanisms necessary to restore lower extremity function and protect the long-term health of articular cartilage following injury.” Blood-flow restriction training, less resistance higher level of reps under supervised care may be the answer.

When you are not responding to traditional conservative care

For most people, surgery will only be considered when standard, traditional conservative care options have failed. However, it should be noted, even then surgery is considered a rare recommendation. It is only when the patella continues to dislocate or can no longer be put back into its groove will surgery be indicated. A common surgical recommendation would be a lateral release which cuts the lateral ligaments that may be pulling the patella out of the groove. This surgery is often performed with other surgeries including  a tibial tubercle osteotomy. The bottom of the thigh bone, the tibial tubercle is reshaped and held together with screws. This surgery helps put the patella back into the groove.

Patellar stabilization surgeries

In some instances and as discussed above surgical treatment may be necessary when patella dislocation becomes chronic and degenerative wearing away of the bone is occurring.

Surgeries that may be recommended include:

  • Arthroscopic lateral-release. The ligaments that hold the knee cap in place are cut to relax their grip on the knee cap and allow it to resume its rightful place within the trochlear groove.
  • Medial patellofemoral ligament reconstruction. This surgery is typically reserved for complete or almost complete tear of the ligament. Typically grafts from the hamstring tendons are used in place of the ligament. This is a very major procedure.
  • Knee osteotomy (tibial tubercle transfer) is an open (non-arthroscopic) surgery that shaves down and remodels bone that seeks to reshape the knee in a more natural anatomy. This is a very major procedure.

An August 2021 paper (6)  analyzed the effectiveness of a Trochleoplasty, another patella stabilizing surgery. The trochlear groove (where the patella should sit) is made deeper. In many cases a medial patellofemoral ligament reconstruction is performed at the same time. The research team noted: “Trochleoplasty is an effective patellar stabilization procedure; however, it is associated with a risk of complications that cannot be ignored.” In this paper the researchers rexamined past studies of various trochleoplasty procedures “to specify: (1) the recurrence rate of patellofemoral dislocation; (2) the complication rates and; (3) the clinical outcomes.”

They did find a low recurrence rate for patellofemoral dislocation and residual instability. But, “The incidence of stiffness, patellofemoral osteoarthritis and subsequent surgery remains high but differs greatly between studies. This meta-analysis showed a very large disparity between studies for most complications, which justifies the need for randomized and comparative studies to establish the role of trochleoplasty procedures in the treatment algorithm for patellar instability.”

A February 2022 paper (7)  examined active duty military personnel who had patella stabilization surgery and assessed their long-term outcomes with their patellar stabilization surgeries. In this paper a retrospective review of a consecutive series of 63 patients who underwent operative management for patellar instability at a military medical center between 2003 and 2017.

All cases were performed by a single sports medicine fellowship-trained orthopaedic surgeon. Patients with recurrent lateral patellar instability whose nonoperative management failed were included. All patients underwent arthroscopic imbrication of the medial patellar retinaculum (loosening of the ligaments), an open lateral retinacular release (to get a tilted knee cap back in place), and an Elmslie-Trillat tibial tubercle osteotomy (bone was shaved down).

Outcome measures at final follow-up included recurrent instability, need for surgical revision, subjective assessments (did it help?), and military-specific metrics (were the military personnel able to resume their military functions).

  • A total of 51 patients were included (34 men, 17 women; average age 27 tears old).
    • Four patients (7.8%) reported redislocation events, and 4 underwent revision surgery.
    • Twenty-five patients (49.0%) reported a decrease in activity level as compared with preinjury, while 10 (19.6%) cited restrictions in activities of daily living.
    • Of the 21 patients remaining on active duty, 6 (28.6%) required an activity-limiting medical profile.
    • Of the 48 active duty patients, 12 (25.0%) underwent evaluation by a medical board for separation from the military.


1 Hayat Z, El Bitar Y, Case JL. Patella dislocation. StatPearls [Internet]. 2021 May 5.
2 Wierer G, Krabb N, Kaiser P, Ortmaier R, Schützenberger S, Schlumberger M, Hiller B, Ingruber F, Smekal V, Attal R, Seitlinger G. The Patellar Instability Probability Calculator: A Multivariate-Based Model to Predict the Individual Risk of Recurrent Lateral Patellar Dislocation. The American Journal of Sports Medicine. 2022 Jan 21:03635465211063176.
3 Małecki K, Fabiś J, Flont P, Fabiś-Strobin A, Niedzielski K. Assessment of knee flexor muscles strength in patients with patellar instability and its clinical implications for the non-surgical treatment of patients after first patellar dislocation – pilot study. BMC Musculoskelet Disord. 2021 Aug 28;22(1):740. doi: 10.1186/s12891-021-04636-4. PMID: 34454460.
4 Habersack A, Kraus T, Kruse A, Regvar K, Maier M, Svehlik M. Gait Pathology in Subjects with Patellofemoral Instability: A Systematic Review. International Journal of Environmental Research and Public Health. 2022 Jan;19(17):10491.
5 Brightwell BD, Stone A, Li X, Hardy P, Thompson K, Noehren B, Jacobs C. Blood flow Restriction training After patellar INStability (BRAINS Trial). Trials. 2022 Dec;23(1):1-8.
6 Leclerc, J.T., Dartus, J., Labreuche, J., Martinot, P., Galmiche, R., Migaud, H., Pasquier, G. and Putman, S., 2021. Complications and Outcomes of Trochleoplasty for Patellofemoral Instability: A Systematic Review and Meta-analysis of 1000 Trochleoplasties. Orthopaedics & Traumatology: Surgery & Research, p.103035.





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