AXIAL COMPUTED-TOMOGRAPHY OF THE PATELLOFEMORAL JOINT WITH AND WITHOUT QUADRICEPS CONTRACTION

Computed tomography was used to analyze the patellofemoral relationshi p during the first 60 degrees of knee flexion in patients with chronic patellofemoral pain syn drome (49 knees) and a healthy control group (15 knees). The patellofemoral joints were imaged axially through the center of the patella articular cartilage with the knee flexed 0 degre es, 0 degrees with maximal quadriceps muscle contraction, 30 degrees, and 60 degrees. In 0 degrees of knee flexion, the sulcus angle was gre ater in the symptomatic group than in normal controls. The patella dis placed further laterally, and the lateral patellar tilt was greater. T he patellar lateral index was found to be greater at 0 degrees and ind icated severe abnormality with full quadriceps muscle contraction. The Laurin angle was pathologic with increased medial opening, especially with muscle contraction. At 30 degrees of knee flexion, these differe nces were less marked than at 0 degrees. No relevant differences were found with 60 degrees of knee flexion. This study showed that the sulc us angle, lateral patellar displacement, lateral patellar tilt, patell a lateral condyle index, and Laurin angle are relevant diagnostic feat ures in 0 degrees of knee flexion, indicating a pathological femoral p atellar gliding mechanism. Our evaluation also demonstrated the influe nce of full quadriceps muscle contraction, especially regarding latera l patellar displacement and the Laurin angle, and it was most prominen t on the patella lateral condyle index. Thus, quadriceps muscle contra ction often creates a more pathological displacement of the patella, w hich can be depicted using axial computed tomography.