In temporomandibular joints (TMJs), the disc and condylar cartilage function as load-bearing, shock-absorbing, and frictionreducing materials. The ultrastructure of the TMJ disc and cartilage is different from that of hyaline cartilage in other diarthrodial joints, and little is known about their lubrication mechanisms. In this study, we performed micro-tribometry testing on the TMJ disc and condylar cartilage to obtain their region-and direction-dependent friction properties. Frictional tests with a migrating contact area were performed on 8 adult porcine TMJs at 5 different regions (anterior, posterior, central, medial, and lateral) in 2 orthogonal directions (anterior-posterior and medial-lateral). Some significant regional differences were detected, and the lateral-medial direction showed higher friction than the anterior-posterior direction on both tissues. The mean friction coefficient of condylar cartilage against steel was 0.027, but the disc, at 0.074, displayed a significantly higher friction coefficient. The 2 tissues also exhibited different frictional dependencies on sliding speed and normal loading force. Whereas the friction of condylar cartilage decreased with increased sliding speed and was independent of the magnitude of normal force, friction of the disc showed no dependence on sliding speed but decreased as normal force increased. Further analysis of the Péclet number and frictional coefficients suggested that condylar cartilage relies on interstitial fluid pressurization to a greater extent than the corresponding contact area of the TMJ disc.

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modification program (Table 1). This was associated with an average 6.7 degree increase in self-selected toe-out angle (p < 0.001) and 10% reduction in the late stance KAM (p ¼ 0.04). Participants reported that difficulty in achieving the desired toe-out angle significantly decreased over the course of the program. Joint discomfort was reported by five participants (33%) in the hip or knee joints, though none lasted longer than two weeks. Conclusion: Results from the current study provide preliminary evidence as to the benefits of toe-out gait modification training in individuals with medial knee OA. Specifically, these findings suggest that gait modification can significantly improve clinical and biomechanical outcomes relevant to medial compartment knee OA. This study also showed that gait modification can be successfully delivered with minimal difficulty or consequences to other lower limb joints. Future research utilizing more participants and a control group are now needed to best understand the biomechanical and clinical changes following toe-out gait modification.