Dynamic biomechanical effects of anterior cruciate ligament deficiency and reconstruction on patellofemoral joint contact characteristics: An in vitro study.

Abstract

Anterior cruciate ligament (ACL) injury alters knee kinematics and may disrupt patellofemoral (PF) joint loading. Although anterior cruciate ligament reconstruction (ACLR) restores tibiofemoral stability, most previous studies have evaluated PF mechanics under static or quasi-static conditions, leaving the dynamic effects of ACL deficiency and reconstruction insufficiently characterized. The present study, therefore, used a dynamic loading protocol to investigate PF contact mechanics during knee flexion. Twenty porcine knees were tested sequentially in ACL-intact, ACL-deficient, and ACL-reconstructed states. A constant 100 N quadriceps load was applied during dynamic knee flexion. PF mean contact area, mean contact pressure, and peak contact pressure were measured at 30°, 60°, and 90°. Data were analyzed using a two-way repeated-measures ANOVA to assess the effects of condition and flexion angle, including their interaction, with Bonferroni-adjusted post hoc comparisons. ACL deficiency significantly reduced PF mean contact area and increased mean and peak contact pressures (p < 0.05). ACLR partially restored PF mechanics, with peak contact pressure and lateral mean contact area approaching levels comparable to those in the intact condition. However, residual abnormalities persisted in the medial mean contact area and mean contact pressure. Significant interaction effects indicated that these alterations were more pronounced at higher flexion angles. ACL deficiency alters PF load distribution and induces localized overloading during dynamic knee flexion. Although ACLR partially restores PF mechanics, residual abnormalities persist, particularly in mean contact pressure. These findings may have implications for persistent PF symptoms after ACLR, but require validation in longitudinal clinical studies.