Static and dynamic analysis of patellofemoral joint arthritis using computed tomography

Twelve parameters of the knee were evaluated using computed tomography to analyze possible etiological mechanisms leading to patello-femoral arthritis (PF-OA). Sixteen normal knees and 14 knees with PF-OA were tested. CT scans were taken at the level of the femoral epicondyles, the tibial tubercle and the malleoli of the ankle joint at full extension and 30deg of flexion. The slices were superimposed and three parameters; tibial tubercle rotation angle (TT angle), malleolar line rotation angle (ML angle) and tibial tubercle and lateral condyle angle (TT-LC angle) were measured with the central point of the medial and lateral epicondyle line as the fiducial point. Differences in each parameter between full extension and 30deg of flexion were also evaluated as dynamic factors. Three other parameters, lateral condyle rotation angle (LC angle). Lateral and medial condyle angle (LC-MC angle) and lateral condyle and patellar groove angle (LC-S) were also measured to evaluate the anatomical configuration. The position of the tibial tubercle at full extension relative to the femoral condyle was almost the same in both groups. The results, however, demonstrated that, in the PF-OA knee, the tibial tubercle stayed more lateral compared with the normal knee at 30deg of flexion. It is obvious that the tibial tubercle exists laterally in knee flexion and the patella impinges against the lateral femoral condyle in knee flexion which will cause PF-OA. (author)