In situ compressive stiffness, biochemical composition, and structural integrity of articular cartilage of the human knee joint

Objective: Reduction of compressive stiffness of articular cartilage has be en reported as one of the first signs of cartilage degeneration. For the me asurement of in situ compressive stiffness, a hand-held indentation probe h as recently been developed and baseline data for macroscopically normal kne e joint cartilage were provided. However, the histological stage of degener ation of the measured cartilage was not known. The purpose of this study wa s to investigate whether there is a relationship between the in situ measur ed compressive stiffness, the histological stage of degeneration, and the b iochemical composition of articular cartilage. Design: Instantaneous compressive stiffness was measured for the articular cartilage of 24 human cadaver knees. Additionally, biochemical composition (total proteoglycan and collagen content) and histological appearance (acco rding to the Mankin score) were assessed for each measurement location. Results: Despite visually normal surfaces, various histological signs of de generation were present. A high correlation between Mankin score and cartil age stiffness was observed for the lateral patellar groove (R-2=0.81), the medial (R-2=0.83) and the lateral femoral condyle (R-2=0.71), whereas a mod erate correlation was found for the medial patellar groove (R-2=0.44). No c orrelation was observed between biochemical composition and cartilage compr essive stiffness. Conclusions: Our results are in agreement with others and show that the ins tantaneous compressive stiffness is primarily dependent on the integrity of the extracellular matrix, and not on the content of the major cartilage co nstituents. The high correlation between stiffness and Mankin score in mild osteoarthrosis suggests that the stage of cartilage degeneration can be as sessed quantitatively with the hand-held indentation probe. Moderate and se vere case of osteoarthrosis remains to be investigated. (C) 2001 OsteoArthr itis Research Society.