Worse Tibiofemoral Cartilage Composition Is Associated with Insufficient Gait Kinetics After ACL Reconstruction

Purpose: Greater articular cartilage T1 rho magnetic resonance imaging relaxation times indicate less proteoglycan density and are linked to posttraumatic osteoarthritis development after anterior cmciate ligament reconstruction (ACLR). Although changes in T1 rho relaxation times are associated with gait biomechanics, it is unclear if excessive or insufficient knee joint loading is linked to greater T1 rho relaxation times 12 months post-ACLR. The purpose of this study was to compare external knee adduction (KAM) and flexion (KFM) moments in individuals after ACLR with high versus low tibiofemoral T1 rho relaxation profiles and uninjured controls. Methods: Gait biomechanics were collected in 26 uninjured controls (50% females; age, 22 +/- 4 yr; body mass index, 23.9 +/- 2.8 kg.m(-2)) and 26 individuals after ACLR (50% females; age, 22 +/- 4 yr; body mass index, 24.2 +/- 3.5 kg.m(-2)) at 6 and 12 months post-ACLR. ACLR-T1 rho(High) (n = 9) and ACLR-T1 rho(Low) (n = 17) groups were created based on 12-month post-ACLR T1 rho relaxation times using a k-means cluster analysis. Functional analyses of variance were used to compare KAM and KFM. Results: ACLR-T1 rho(High) exhibited lesser KAM than ACLR-T1 rho(Low) and uninjured controls 6 months post-ACLR. ACLR-T1 rho(Low) exhibited greater KAM than uninjured controls 6 and 12 months post-ACLR. KAM increased in ACLR-T1 rho(High )and decreased in ACLR-T1 rho(Low) between 6 and 12 months, both groups becoming more similar to uninjured controls. There were scant differences in KFM between ACLR-T1 rho(High) and ACLR-T1 rho(Low) 6 or 12 months post-ACLR, but both groups demonstrated lesser KFM compared with uninjured controls. Conclusions: Associations between worse T1 rho profiles and increases in KAM may be driven by the normalization of KAM in individuals who initially exhibit insufficient KAM 6 months post-ACLR.