Magnetic resonance imaging-based morphological and alignment assessment of the patellofemoral joint and its relationship to proximal patellar tendinopathy

Objective To assess the differences in morphology and alignment of the knee between patients with proximal patellar tendinopathy (PPT) and a control group, using MRI and focusing on the patellofemoral joint. Methods We retrospectively included 35 patients with clinically diagnosed and unequivocal findings of PPT on knee MRI, the case group. For the control group, we included 70 patients who underwent knee MRI for other reasons, with no clinical or MRI evidence of PPT. Patients and controls were matched for age and gender, with all subjects reporting frequent physical activity. MRIs were evaluated by two musculoskeletal radiologists, who assessed parameters of patellar morphology, trochlear morphology, patellofemoral alignment, and tibiofemoral alignment. The differences in parameters between cases and controls were assessed using Student's t test. Logistic regression was applied to assess the associations between the MRI parameters and the presence of PPT. Results The patellar height Insall-Salvati ratio was different between cases and controls (1.37 +/- 0.21 vs. 1.24 +/- 0.19; p = 0.003). The subchondral Wiberg angle was higher in cases than controls (136.8 +/- 7.4 vs. 131.7 +/- 8.8; p = 0.004). After applying logistic regression, significant associations with PPT were found [odds ratios (95% CI)] for patellar morphology [1.1 (1.0, 1.2)] and patellar height [1.3 (1.0, 1.7)]. Conclusions Patellar height and the subchondral patellar Wiberg angle were greater in patients with PPT and significantly associated with PPT.