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Patellar subluxation is a condition of the kneecap. It is not the same as patellar dislocation, which occurs when the kneecap pops out of its normal position and will not return to that position unless it is manually replaced. Patellar subluxation typically occurs when the kneecap is not moving properly and tends to slip in and out of its proper position. Knee pain can occur with this condition, and the kneecap may make clicking sounds or may move palpably from its normal position and back again. Patellar subluxation can increase the risk of kneecap dislocation, and is usually treated with a combination of stabilizing braces and strengthening exercises.
The kneecap, or patella, is commonly identified as the small circular bone on the front of the knee, at the joint where the femur meets the tibia. The femur typically has a groove or channel in which the kneecap normally rests and moves. The normal, healthy kneecap should move only vertically within this channel.
The knee condition known as patellar subluxation occurs when the knee moves horizontally out of this channel. This can occur when the knee is injured, especially if a ligament is torn. It can also occur in the absence of injury, generally if the joint is weak or unstable. Women, children, and teenagers are most likely to suffer patellar subluxation due to an unstable or weak knee joint.
Subluxation of the kneecap can cause pain in the knee. The pain is most often felt on the outside edge of the knee, since the patella is most likely to move in that direction. People who experience pain from patellar subluxation may find that pressing inward against the sore part of the knee helps to relieve the discomfort.
When patellar subluxation occurs, the kneecap can generally be felt to be moving from side to side. The joint may produce clicking sounds. Pain generally occurs.
Experts believe that weaknesses in the hip flexors, hip adductors, and quadriceps may contribute to the knee instability that often leads to patellar subluxation. Physical therapy usually seeks to stabilize the knee joint by stabilizing these muscles. Some therapists may recommend using athletic tape or a knee brace to help relieve the symptoms of patellar subluxation, and prevent further knee injury. If symptoms are severe or if patellar dislocation occurs, surgery may be necessary to re-align and stabilize the knee joint.