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Patellar subluxation or dislocation often occurs when an athlete makes a sudden change of direction after planting his or her feet. Use caution when participating in sports that may require these types of motions.

A patellar dislocation occurs when the patella (knee cap) is dislocated from its normal position in a groove between two ridges on the front of the end of the femur (thigh bone). A patellar subluxation is a partial dislocation of the patella.

Causes
Dislocation of the patella can occur during sports when a side-to-side force, typically to the outside of the knee, is applied across the front of the knee. This may happen when a running athlete suddenly plants a foot and makes a sudden change in direction, forcing the knee cap to the outside. A patellar subluxation can occur with similar forces that do not cause a full dislocation. In patients who have a structural predisposition to patellar subluxation, such as very mobile patellae, very valgus (knock kneed) knee alignment or developmental problems with the end of the femur, patellar subluxation can occur even with activities of daily living.

Symptoms
Patellar dislocation or subluxation commonly feels like the kneecap is moving out of position, typically toward the lateral (outer) edge of the knee. This may be accompanied by swelling and pain. The pain is typically on the anterior (front) portion of the knee.

Diagnosis
Your doctor will ask about the history of your knee condition and will examine your knee for the position and stability of the patella. X-rays may be taken to learn more about the position of the patella as well as the shape of the end of the femur and to rule out a fracture.

Treatment

  • Rest . All activities that require active use of the knee should be restricted. Talk with your doctor about a plan for gradually returning to full activity.
  • Ice . Ice packs may be used for about 20 minutes at a time, each hour to help alleviate pain and decrease swelling.
  • Bandage/Compression Wraps . Your doctor may recommend that you use a soft elastic wrap or bandage at the knee to help reduce swelling.
  • Elevation . Elevating the knee should help ease pain and swelling. Ideally, the foot should be elevated higher than the knee, and the knee should be elevated higher than the hip.
  • Medication . Your doctor may prescribe an anti-inflammatory or pain medication.
  • Knee Brace . Your doctor may prescribe a knee brace to help stabilize the joint.
  • Crutches . Your doctor may advise you to use crutches to take pressure off the knee, reduce pain and increase mobility. You should be protected with crutches if weight-bearing is painful or if you are limping.
  • Physical Therapy . Your doctor or physical therapist may recommend a range of motion and muscle stretching and strengthening program for your knee.

Most cases of patellar dislocation/subluxation can be treated without surgery. Arthroscopic or reconstructive surgery may be recommended in more severe cases, such as if the patella continues to dislocate or sublux despite nonoperative treatment, or if the dislocation or subluxation of the patella results in cartilage or bone injury to the patella or femur.

Recovery Outlook
A minor subluxation of the patella, especially if it is not a first-time subluxation, may recover fairly quickly with full recovery in a few days to a few weeks. Ongoing physical therapy and a kneecap stabilizing brace may be required for full recovery and for preventing a recurrence of the injury. If surgery is required to stabilize the patella, the recovery may be quite prolonged and may easily take 3-6 months.

Prevention
Patellar subluxation is best prevented by strengthening the muscles of your thigh, selectively stretching certain structures about the knee as prescribed by your physical therapist and keeping in good shape. Your doctor may also prescribe a brace to help support and stabilize your patella. Orthotics may be helpful for some patients.