Correlating anatomy and congruence of the patellofemoral joint with cartilage lesions.

Cartilage lesion of the patellofemoral joint is a common and challenging disease of the knee and an important cause of anterior knee pain. There are many naturally occurring variations in the anatomy and congruence of the patella and femoral trochlea. The purpose of this study was to identify the variations in patellofemoral anatomy and congruency that predispose to cartilage lesions. Among patients who underwent knee arthroscopy in our center from January 2005 to December 2006, 111 patients with chronic patellofemoral cartilage lesions and anterior knee pain were selected as the lesion group, while 124 patients with isolated meniscus rupture without anterior knee pain were selected as the control group. Twenty-one parameters measured on magnetic resonance images were used to assess the patellofemoral anatomy and congruence. A binary logistic regression model was used to look for possible associations between each of these parameters and the occurrence of patellofemoral cartilage lesions. The Bonferroni correction with a type I error rate of 0.0024 (0.05/21) was adopted to indicate statistical significance. Based on examination of the patellofemoral anatomy, 4 parameters were significantly associated with patellofemoral cartilage lesions. These were the patella lateral facet width, patella lateral facet ratio, sulcus depth and sulcus relative depth (P for linear trend <.0024). For patellofemoral congruence, 3 parameters were significantly associated with patellofemoral cartilage lesions. These were the lateral patella displacement, patella epicondylar axis angle and congruence angle (P for linear trend <.0024). Among the many kinds of patellofemoral variations, several were found to correlate with the development of patellofemoral cartilage lesions. These problems could be important risk factors for patellofemoral cartilage lesions.