Lateral patellar retinaculum hypertrophy on magnetic resonance imaging predicts patellar subluxation in femoral trochlear dysplasia.

Purpose: To explore the magnetic resonance imaging (MRI) features of the medial patellofemoral ligament (MPFL) and lateral patellar retinaculum (LPR) in femoral trochlear dysplasia (FTD) and assess their utility in predicting patellar subluxation (PS). Methods: Eighty patients with patellofemoral pain (30 controls, 32 FTD, 18 FTD + PS) underwent 3.0 T MRI. Axial T2-weighted images were used to measure MPFL/LPR thickness and cross-sectional area (CSA) at 5, 10 and 15 mm from the patellar attachment. Results: Significant differences in MPFL and LPR thickness and CAS existed among groups (all p values < 0.05). LPR metrics showed stronger correlation with lateral trochlear inclination (LTI) than MPFL at all points. LPR thickness at 15 mm correlated most strongly with LTI (r = -0.65). LPR CSA at 15 mm predicted PS (AUC = 0.80). Conclusions: LPR thickness and CSA-particularly from patellar attachment-represent potential predictive indicators for PS in FTD. Level of Evidence: Level III.