Kneecap Dislocation
What Is a Kneecap Dislocation?
The kneecap (patella) normally glides up and down within a groove at the front of the femur as the knee bends and straightens. A kneecap dislocation occurs when the patella slips completely out of this groove, most often shifting toward the outer side of the knee. This is a different, generally less severe injury than a full knee dislocation, which involves the entire joint.
What Causes a Kneecap Dislocation?
- A direct blow to the inner side of the kneecap
- Sudden twisting of the knee while the foot is planted, especially with the knee turning inward
- Pivoting sports, such as basketball, soccer, and gymnastics
- Anatomic factors that make dislocation more likely, including a shallow patellar groove, looser-than-average ligaments, or a kneecap that sits higher than normal
Kneecap dislocations are especially common in adolescents and young adults, and once it happens once, the risk of it happening again increases.
What Are the Symptoms of a Kneecap Dislocation?
- A visible shift of the kneecap out of place at the moment of injury (it sometimes pops back into place on its own before evaluation)
- Immediate, significant pain
- Rapid swelling
- Inability to straighten or bear weight on the leg immediately after injury
- A sense that the knee “gave out” or buckled
Does a Kneecap Dislocation Damage Cartilage?
Often, yes. As the kneecap shifts out of its groove and then relocates, the cartilage on the underside of the patella or the adjacent femur can be scraped or chipped, sometimes creating a loose fragment of bone and cartilage within the joint. This is one reason an MRI is frequently recommended after a first-time kneecap dislocation — to check for cartilage damage that might not be obvious on an X-ray alone.
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Treatment Options for a Kneecap Dislocation
First-time dislocations without a loose cartilage fragment are often treated nonsurgically:
- A period of bracing to allow the supporting ligament on the inner side of the kneecap (the medial patellofemoral ligament, or MPFL) to heal
- Physical therapy to restore strength, particularly of the quadriceps muscles that help stabilize the kneecap
- Gradual return to activity
Surgery may be recommended after repeated dislocations, when a loose cartilage or bone fragment is found in the joint, or when anatomic factors make the kneecap highly prone to dislocating again. Surgical options can include repairing or reconstructing the MPFL, or in some cases, realigning the way the kneecap tracks within its groove.
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Dr. Palsis specializes in the treatment of knee, shoulder, and sports injuries.