Patellofemoral Joint Anatomy Is Associated With Landing Mechanics After Operative Treatment for Patellar Instability.

Background: Patellofemoral instability (PFI) has several known anatomic factors, including trochlear dysplasia and patellar maltracking. While studies have documented altered lower-extremity gait biomechanics in patients with PFI, the relationship between these biomechanical abnormalities and anatomy has not been thoroughly investigated, particularly during sport-related tasks. Purpose/Hypothesis: The purpose of this study is to examine the associations between preoperative anatomic characteristics and lower-extremity kinematics at sports clearance in adolescents after medial patellofemoral ligament reconstruction for PFI. It was hypothesized that patellar maltracking, trochlear dysplasia, and frontal plane malalignment would strongly correlate with abnormal lower-extremity biomechanics. Study Design: Descriptive laboratory study. Methods: Patients aged 10 to 18 years who underwent primary medial patellofemoral ligament reconstruction for PFI between 2019 and 2023 were tested at sports clearance visits. Joint angles of the hip and knee were calculated during descent of a drop vertical jump. Preoperative radiographs and magnetic resonance imaging were utilized to record tibial tuberosity-trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance, trochlear width (TW), trochlear sulcus depth (TSD), lateral inclination angle, patellar tilt angle (PTA), Caton-Deschamps Index (CDI), and femorotibial angle. Spearman correlations assessed relationships between preoperative anatomy and drop vertical jump kinematics. Results: In total, 17 participants were tested (8 male, 15 unilateral; mean ± SD age, 15.5 ± 1.4 years; height, 166.3 ± 11.4 cm; weight, 65.1 ± 19.4 kg; days after surgery, 199.9 ± 30.8). TT-PCL, TT-TG, and TSD were not significantly correlated with kinematics. Greater dynamic pelvic obliquity (r = 0.672; P = .004) and internal pelvic rotation (r = 0.508; P = .044) were positively correlated with femorotibial angle. Pelvic obliquity was negatively correlated with CDI (r = -0.710; P = .007). Greater severity of patellar malalignment and trochlear dysplasia (decreased TW, r = -0.486 [P = .048]; increased PTA, r = 0.689 [P = .002]) was associated with greater hip abduction. TW (r = 0.503; P = .040) and CDI (r = -0.608; P = .028) were also correlated with internal hip rotation. Greater knee flexion during landing was correlated with decreased PTA (r = -0.547; P = .023) and CDI (r = -0.560; P = .046). Greater dynamic knee valgus was positively correlated with TW (r = 0.483; P = .049), and greater internal knee rotation was positively correlated with lateral inclination angle (r = 0.513; P = .035). Conclusion: Larger degree of patellar maltracking, trochlear dysplasia, and frontal plane malalignment correlated to distinct biomechanical patterns during dynamic movements. Statistically significant associations were found with internal knee and hip rotation, pelvic instability, hip abduction, and knee stiffness. Conversely, TT-PCL, TT-TG, and TSD demonstrated no significant association with postoperative kinematic patterns in patients with PFI. Clinical Relevance: Understanding how anatomic abnormalities relate to postoperative biomechanics can help clinicians identify adolescents at risk for persistent movement deficits after medial patellofemoral ligament reconstruction. These findings highlight the importance of incorporating individualized anatomic considerations into postoperative rehabilitation and return-to-sport assessments.