Patellofemoral problems after intraarticular anterior cruciate ligament reconstruction.

A series of 226 anterior cruciate ligament (ACL) reconstructions were reviewed to determine the incidence of patellofemoral (PF) problems and the associated prognostic factors. Patients were divided into four groups according to the type of injury (acute or chronic) and operation (through an arthrotomy or arthroscopic assisted). The average follow-up period was 39 months. Overall there was a 5% incidence of PF crepitus with pain and/or swelling, and a further 20% of clear PF crepitus without pain. The change from open surgery and cast to arthroscopic surgery and early motion allowed a decrease of PF problems from 40% to 21% in acute injuries, but the difference was less marked in chronic knees. A deficit greater than 10% at the one-leg hop test was present in 75% of the knees with PF crepitus and pain. The height of the patella was increased in 5% and decreased in 17% of the knees. Patients with rehabilitation difficulties had the largest decrease in patella height, whereas a patella alta was more frequent after patellar tendon reconstruction. A significant correlation was found between PF problems and female gender, positive congruence angle, preoperative PF crepitation, rehabilitation difficulties, flexion loss greater than 10 degrees, extension loss greater than 5 degrees, and variation in the height of the patella. The importance of avoiding immobilization, rehabilitation difficulties, and permanent flexion or extension loss is emphasized.