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Knee

Patellar Dislocation

Patellar (kneecap) dislocations occur with significant regularity, especially in younger athletes, with most of the dislocations occurring laterally (outside). When these happen, they are associated with significant pain and swelling. Following a patellar dislocation, the first step must be to relocate the kneecap into the trochlear groove. This often happens spontaneously as the individual extends the knee either while still on the field of play or in an emergency room or training room as the knee is extended for examination. When relocation occurs before examination, its occurrence must be solved by finding related problems.

Associated problems normally occur with patellar dislocations, the most obvious of which is tearing of the ligaments that stabilize the kneecap itself. As is the case with all other joints, ligamentous disruption or tearing occurs to allow the joint to dislocate. In the case of patellar dislocation, the ligaments on the inside of the knee are the most commonly injured as the kneecap slides laterally.

While tearing of these ligaments is unfortunate, they do have the potential to heal. Of much more concern are the small fragments of cartilage and bone that often are knocked off of the kneecap or the lateral femoral condyle during the relocation of the kneecap. These fragments become loose bodies and usually require removal during an arthroscopic procedure. Patellar dislocations can also cause significant quadriceps muscle injuries, which can be made worse due to the effusion within the knee or to early onset of exercises and premature return to play.

Causes

Patellar dislocations can occur either in contact or non-contact situations. An athlete can dislocate his/her patella when the foot is planted and a rapid change of direction or twisting occurs. Usually a pre-existence ligamentous laxity is required to allow a dislocation to occur in this manner. Direct blows to a knee can cause dislocations as well. The force of these is obviously much greater and usually causes more severe damage especially to restraining ligaments.

Symptoms

Typical symptoms include:

  • Rapid, acute swelling.
  • Extreme pain initially until relocation occurs.
  • Continued pain along medial (inside) ligaments.
  • Discoloration medially at site of ligament injury.
  • Sense of instability and apprehension that problem will recur.

Treatment

Normal care of patellar dislocations when a loose fragment has not been created is the immobilization of the knee for a short period of time (seven to 10 days). During this time, the swelling is reduced, and the acute discomfort of the dislocation decreases. The healing process requires slow mobilization of the knee and the patellofemoral joint, and full recovery can usually be expected within a three to six week period.

This period of time is significantly lengthened when the patellar dislocation is recurrent, which is often expected is situations where hyperlaxity of the ligaments exists. Conservative management of these problems in season with appropriate rest, appropriate hip and thigh muscle strengthening, and perhaps the use of a patellar buttress brace is appropriate.

Alternative treatments can include glucosamine, hyaluronic acid, and non-steroidal anti-inflammatory medications (NSAIDs).

Some situations of patellar dislocation, such as when recurrent dislocations occur, can and/or should be treated surgically. In these situations, to limit the amount of lost time in competition and to reduce the chances for cartilage lesions on the undersurface of the patella—which often are non-repairable—patellar stabilization procedures are appropriate. These procedures can be either soft tissue or bone procedures, or a combination thereof.

It has been found in retrospective studies that the incidence of recurrent dislocation after the first dislocation occurs can be as high as 40 percent. Surgically treating those dislocations by lessening lateral tension and tightening medial restraint could reduce this recurrence rate to below 10 percent.

Surgical procedures on the patella are usually done in the outpatient setting. Procedures limited to altering soft-tissue tension begin rehabilitation within a week and return to activity can be expected as early as six weeks. Procedures that require bone work (osteotomies) require a period of relative immobilization and need 10 to 12 weeks before a return to athletic activity is permitted.