Osteoarthritic changes in the biochemical composition of thumb carpometacarpal joint cartilage and correlation with biomechanical properties.

The biochemical composition and biomechanical properties of articular cartilage from 53 human thumb carpometacarpal (CMC) joints from cadavers aged 20 to 79 years were measured and studied in normal, mildly fibrillated, and advanced osteoarthritic (OA) joints. Statistical analyses were performed to determine the correlations between the compositional measures and biomechanical properties. For these CMC joint tissues we found that water content increased, proteoglycan content decreased, and collagen content per dry weight remained unaltered with progression of OA degeneration. We also found that with disease progression, as defined by an OA staging score, the aggregate modulus (ie, compressive stiffness) decreased, along with an unexpected moderate decrease in permeability. This latter finding appears to be specific to CMC cartilage degeneration since articular cartilage from knees and hips generally demonstrates an increase in permeability with water content and OA score. Correlations between biochemical composition and biomechanical properties were found to be stronger in joints with OA than in joints without OA. This finding suggests that OA changes in biochemical composition, relative to baseline normal values, directly affect the biomechanical properties of cartilage, even though the baseline compositional values themselves do not directly determine the magnitude of the biomechanical properties in normal tissue.