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Patella Dislocation

What is the patellofemoral joint?

The patellofemoral joint is the front part of the knee joint, where the patella (kneecap) meets the trochlea of the femur (groove on the end of the thighbone). The patella normally slides up and down in the trochlear groove as the knee bends and straightens. It is held in the center of the groove by the surrounding muscles and ligaments.

What causes a patella dislocation?

Patella dislocation occurs when the patella shifts to the side and out of the trochlear groove. The direction of dislocation is almost always lateral (toward the outside). The first time a patella dislocation occurs, a significant force is required. This often occurs when landing from a jump or cutting during sports. After the first dislocation, repeat dislocations may occur more easily.

What are the symptoms of a patella dislocation?

When the patella dislocates, it may quickly slip back into place, resulting in a quick succession of clunks felt in the front of the knee. Other times, the patella may remain dislocated until the knee is fully straightened. Straightening the knee relieves tension in the front of the knee and allows the patella to move back into the normal central position. In either case, the result is generally pain in the front of the knee, swelling, and stiffness.

What damage occurs with patella dislocation?

When the patella shifts laterally, the ligament that holds the patella in place on the medial side of the knee – known as the medial patellofemoral ligament, or MPFL – is stretched or torn. In addition, bone bruises or cartilage injury may occur. Cartilage injury may result in a loose piece of cartilage in the knee.

How is a patella dislocation diagnosed?

Dr. Driscoll will discuss your symptoms with you and perform a thorough physical examination of your knee. X-Rays are usually obtained to assess alignment and look for evidence of fracture or loose pieces of bone and cartilage that are occasionally chipped off during a patella dislocation. MRI may also be necessary to further evaluate the injury.

What is the treatment for patella dislocation?

Treatment options include non-surgical and surgical alternatives. Non-surgical treatment is most often selected following a “first-time” patella dislocation, and includes physical therapy, bracing, and activity modification. Risk of another patella dislocation after non-surgical treatment is about 40%. Surgery may be required after an initial patella dislocation if a loose body is present in the knee.

Recurrent patella dislocation often requires surgery to stabilize the joint and reduce the risk of additional injury. This most often involves MPFL reconstruction, which recreates the ligament that prevents the patella from shifting laterally. Occasionally, bone realignment is also necessary. You and Dr. Driscoll will discuss your individual situation and create a treatment plan tailored for you.