A MOVING CONTACT OF ARTICULATION ENHANCES THE BIOSYNTHETIC AND FUNCTIONAL RESPONSES OF ARTICULAR CARTILAGE.

Biomechanical influences play a fundamental role in the structural, functional, and biosynthetic properties of articular cartilage. During physiologic joint loading, the contact area between two surfaces migrates due to the primary and secondary motions of the joint. It has been demonstrated that a migratory contact area plays a critical role in reducing the coefficient of friction at the cartilage surface. However, a detailed analysis of the influences that a migratory contact area plays on the structural, functional, and biosynthetic properties remain to be explored. In this study, bovine cartilage explants were placed in a biotribometer. Explants were subjected to compression and shear forces of migratory contact area, namely moving contact (MC) articulation, or stationary contact area, namely stationary contact (SC) articulation. Free swelling explants were used as control. In a separate study, bovine cartilage-bone grafts were used for frictional testing. On histologic analysis, the SC group had evidence of surface fibrillations, which was not evident in the MC group. Compared to the SC group, the MC group cartilage explants had increased chondrocyte viability, increased lubricin synthesis, and comparable proteoglycan synthesis and release. MC articulation had reduced coefficient of friction as compared to SC articulation. MC articulation led to reduced surface roughness as compared to SC articulation. In conclusion, a migratory contact area can play an important role in maintaining the structural, function, and biosynthetic properties of articular cartilage. This study provides further evidence of the importance of migratory contact area and in vitro assessment of natural joint movement, which can be further evaluated in the context of cartilage homeostasis and disease.