Clinical characteristics of patellar disorders in young athletes.

The clinical histories of 50 young athletes who complained of patellar instability or pain were analyzed, and their physical findings were compared to those of 50 controls. The patients were divided into three groups, based on their symptoms. Analysis of their physical findings confirmed the validity of these divisions. Those who complained of frank dislocation of the patella exhibited the most pronounced stigmata of quadriceps dysplasia, including vastus medialis deficiency and infrapatellar fat pad enlargement, and had increased general ligamentous laxity, increased mean patellar mobility, and out-facing patellae with concomitantly decreased Q angles in chronic, recurrent cases. Patients who complained of the classic patellar pain pattern, often called "chondromalacia patella," but who denied swelling were designated CMP. They had normal mean ligamentous laxity and mean patellar mobility, an increased incidence of in-facing patellae with concomitantly increased mean Q angle, and frequently palpable lateral patellofemoral bands. Patients who complained of pain and swelling had physical findings intermediate to the other two groups, and generally correspond to what is usually termed subluxation of the patella. They exhibited normal general laxity but increased mean patellar mobility, normal mean Q angle but an increased incidence of patellar infacing, and fat pad enlargement.