Internal tibial rotation during in vivo, dynamic activity induces greater sliding of tibio-femoral joint contact on the medial compartment

Although extensive research has been conducted on rotational kinematics, the internal/external rotation of the tibio-femoral joint is perhaps less important for protecting joint health than its effect on joint contact mechanics. The purpose of this study was to evaluate tibio-femoral joint contact paths during a functional activity (running) and investigate the relationship between these arthrokinematic measures and traditional kinematics (internal/external rotation). Tibio-femoral motion was assessed for the contralateral (uninjured) knees of 29 ACL-reconstructed individuals during downhill running, using dynamic stereo X-ray combined with three-dimensional CT bone models to produce knee kinematics and dynamic joint contact paths. The joint contact sliding length was estimated by comparing femoral and tibial contact paths. The difference in sliding length between compartments was compared to knee rotation. Sliding length was significantly larger on the medial side (10.2 +/- A 3.8 mm) than the lateral side (2.3 +/- A 4.0 mm). The difference in sliding length between compartments (mean 7.8 +/- A 3.0 mm) was significantly correlated with internal tibial rotation (P < 0.01, R (2) = 0.74). The relationship between rotational knee kinematics and joint contact paths was specifically revealed as greater tibial internal rotation was associated with larger magnitude of sliding motion in the medial compartment. This could suggest that lateral pivot movement occurs during running. Rotational kinematics abnormality should be treated for restoring normal balance of joint sliding between medial and lateral compartments and preventing future osteoarthritis. Prognostic studies, Level II.