Patellar dislocation is an injury of the knee, typically caused by a direct blow or a sudden twist of the leg. It occurs when the patella (kneecap) slips out of its normal position in the patellofemoral groove, and generally causes intense pain with swelling of the knee.
Open or arthroscopic surgery may be used to repair damage, but are typically avoided since rates of re-injury, knee function, and patients’ opinions do not differ much from conservative treatment.
The patella generally dislocates laterally, and can be accompanied by acute pain and disability. Immediate reduction can be accomplished by hyperextension of the knee, and by providing a medialward pressure to move the patella back into the patellofemoral groove. Hyperextension of the knee on its own could possibly move the patella into place, because this motion locks the knee in place.
When the knee is locked the ligaments are twisted and taut, allowing the muscles involved to relax and the patella to slide back into place. If that does not work, a medical professional must manually perform an orthopedic reduction.
Swelling and impaired mobility follow patellar dislocation, and a rehabilitation program of six to sixteen weeks is recommended whether or not the patient undergoes surgery.