Patellar Dislocation

Dislocation of the patella, or kneecap dislocation, is a condition in which the patella (kneecap) moves out of its normal position, usually toward the lateral or outside part of the knee. This condition can cause pain, swelling, and difficulty bending the knee. It occurs more commonly in younger individuals, especially females between the ages of 10 and 16, but it can affect anyone. Dislocation can lead to damage of the patellar cartilage and fractures and can recur.

Dislocation often occurs due to a direct blow to the knee or sudden twisting motion when the foot is planted on the ground, leading to the patella sliding out of the trochlear groove. This is often accompanied by tearing or stretching of the ligaments that stabilize the patella, particularly the medial patellofemoral ligament (MPFL), which is a key structure in preventing lateral dislocations of the patella.

Symptoms include:

• Pain, often severe, at the time of injury
• Swelling of the knee joint
• Visible deformity, with the patella appearing out of place
• Difficulty bending the knee and bearing weight on the affected leg
• A feeling of the patella being unstable

A thorough history and physical examination are necessary to diagnose a patella dislocation and its potential causes. Often, the patella either goes back into position on its own soon after the injury or can be put back into place (for example, in the emergency room). Your UCSF Women’s Sports Medicine specialist will evaluate the knee joint for tenderness and swelling, check the knee range of motion, and evaluate for risk factors for patellar dislocation, including limb alignment, knee and hip rotation, and joint flexibility.

Imaging tests, such as X-rays, can confirm the dislocation and check for bone fractures. Magnetic resonance imaging (MRI) may be used to evaluate the extent of soft tissue damage, including ligaments, bone, and cartilage injuries.

Initially, treatment involves reduction – manually repositioning the patella to put it in its proper place, followed by immobilization with a brace to improve pain, allow the swelling to resolve, and allow ligaments to heal. RICE – rest, icing, compression, and elevation are also used to reduce pain and swelling. Physical therapy is essential for improving range of motion, strengthening the muscles around the knee, especially the quadriceps muscle, and preventing future dislocations.

If the bone or cartilage is damaged, or if there are repeat dislocations, surgery may be necessary to repair or reconstruct the damaged ligaments and realign the patella.