Patellar (kneecap) dislocations occur with significant regularity, especially in younger athletes. Most of the dislocations occur laterally (outside). When these occur, they are associated with significant pain and swelling. Following a patellar dislocation, the first step must be to relocate the patella 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. Occasionally relocation of the patella occurs spontaneously before examination and its occurrence must be inferred 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 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.
A condition referred to as patellar subluxation also exists. The problem exists on a continuum between patellofemoral malalignment and patellar dislocation. It can be sequelae of a traumatic dislocation or in situations where patellar hyper laxity exists. A subluxation is a partial dislocation in which the patella attempts to dislocate but does not do so completely. Situations such as these are very disconcerting and often give the patients a sense of giving way or buckling. At a minimum, these situations should be treated with aggressive therapeutic intervention as the constant subluxation events not only will interfere with competition, but will also potentially cause repeated wear and discomfort within the patellofemoral joint.
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, typically when pushing off and twisting the involved leg toward the athlete’s other side. 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 naturally include extreme pain initially felt at the dislocation that is dramatically relieved upon relocation of the patella back into the trochlea groove. Rapid acute swelling ensues, usually within an hour. Apprehension persists, lack of confidence with weightbearing may occur, and the patient will often complain of continued pain along the medial ligaments along the anterior knee. Eventually discoloration and/or bruising may set into the medial side of the knee adjacent to the medial patellofemoral ligament. The sense of instability and apprehension will often recur without appropriate 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 (10‑14 days). During this time, the swelling is reduced and the acute discomfort of the dislocation decreases. Slow mobilization of the knee and of the patellofemoral joint is then begun, a patellar tracking orthosis or patellar buttress brace is then fitted, and usually functional recovery can be expected within a three to six week period. This period of time is significantly lengthened when the patellar dislocation is recurrent.
Unfortunately, once a patellar dislocation occurs, especially when it occurs in a situation where hyper laxity of the ligaments exists, which is commonly the case, recurrent dislocations can be expected. These are significantly problematic for athletes as they often come in the midst of the season. Non‑operative 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. Without particular calendar goals of haste return to play, brace treatment and rehab may be even more reliably successful. Regardless of all of this, recurrent instability of the patella is a common occurrence.
Some situations of patellar dislocation can and/or should be treated surgically. One situation is when recurrent dislocations occur. 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‑reparable, patellar stabilization procedures are appropriate. First‑time traumatic patellar dislocations can also be treated with surgery, and in chosen situations doing so may be appropriate. These procedures can be either soft tissue or bone procedures, or a combination thereof. An experienced sports medicine trained orthopedic surgeon will assess patients thoroughly to determine what surgical procedure for patellar stabilization gives each individual patient the best chance at long term success and continued stability.
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.
Dr. Mullen performs these surgical procedures on the patella in the out‑patient setting. Procedures limited to altering soft‑tissue tension may begin rehabilitation within a week and return to activity can be expected as early as six weeks. Reconstruction of the medial patellofemoral ligament (MPFL) has become a more successful and popular surgical option, but they and 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.