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Unstable Kneecap


The kneecap or patella is part of the extensor mechanism, which is in charge of bringing your knee up straight when bent. The kneecap runs inside of a groove located in the femur or thigh bone. As long as your kneecap stays in its groove in the knee, you can walk, run, sit, stand, and move easily. When the kneecap slips out of the groove, problems and pain often result.

When the quadriceps (part of the extensor mechanism) is weak or when the groove is uneven or too shallow, the kneecap can slide off, resulting in a partial or complete dislocation. A direct blow to the kneecap when falling or practising contact sports, can also pop the kneecap out of place. This occurs more commonly in young women due to their anatomy and soft tissue laxity.


  • Knee buckles forcing you to fall
  • Knee catches during movement
  • Pain in the front of the knee that increases with activity
  • Pain when sitting
  • Stiffness
  • Cracking sounds during movement
  • Swelling


Diagnosis is performed with a combination of a medical history, a physical examination and imaging tests, such as X-rays, MRI and CT scans.
Most of the times, this condition is successfully managed with lifestyle modifications, analgesics, sporting technique re-training and physiotherapy. Taping and/or braces can be used as well during recreational activities. Exercises to strengthen the muscles in your thigh to keep the kneecap aligned, is a key component of the rehabilitation.
When rehabilitation fails or when a cartilage fragment is free in the knee, arthroscopy or keyhole surgery will be recommended. This may be associated with other procedures to re-balance the kneecap.