Marc Darrow MD,JD

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

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. Indeed, for many people, their knee problems began with a traumatic patellar dislocation as a result of an impact injury to the knee. For others their knee problems progressed to such a degenerative state that many different diagnosis could be made on the same knee including one of  chronic patellar instability or chronic patella subluxation.

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.

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.”

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. (2)

“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.”

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.

An August 2021 paper (3)  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.”

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References

1 Hayat Z, El Bitar Y, Case JL. Patella dislocation. StatPearls [Internet]. 2021 May 5.
2 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.
3 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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