Kneecap (Patellar) Dislocation


Also called patellar sublimation, patients who experience an unstable kneecap have a patella that does not track evenly within its groove on the femur. Depending on the severity, this improper tracking may not cause the patient any problems, or it may lead to dislocation of the patella (where the kneecap fully dislocates out of joint). Patellar sublimation and dislocation are conditions that usually affect adolescents, and sometimes younger children.


Symptoms of kneecap dislocation include:

  • Tenderness and swelling on and around your knee
  • Discomfort when you are active
  • Pain over the edges of the kneecap
  • Collapsing or giving-way of the knee that sometimes causes you to fall

Causes and Risk Factors

It is common for a kneecap dislocation to occur after a high-impact injury. After the first time, the kneecap is more likely to dislocate again. Young people, such as adolescents who are more active, are at a greater risk of having a dislocated kneecap.


The doctor will examine the knee and diagnose a patellar dislocation after a clinical examination. X-rays are also done to confirm the injury and possible other injuries or fractures.

Treatment of the unstable patella is first to ensure that the patella is not dislocated. If it is, your doctor will need to properly 'reduce,' or reorient, the position of the kneecap.

Early treatment includes:

  • Physical Therapy with an emphasis on strengthening the quadriceps (the muscles of the thigh)
  • Bracing and taping - Special knee braces are designed to control how the kneecap moves.
  • Surgery - Some patients may need surgery, especially if they have a lot of pain or repeated dislocations. Sometimes the surgeon will look in the knee with an arthroscope. He or she will be able to see how the knee joint works and whether its parts line up together correctly. A common problem comes from having too much sideways pull which moves the kneecap out of its groove. This can place increased pressure on cartilage and lead to dislocation. For this problem, a procedure known as a lateral release can be done. This procedure involves cutting the tight lateral ligaments to allow the patella to resume its normal position.

If repeated dislocations occur, a surgical realignment of the muscles and kneecap may be needed.

© 2000-2021 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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