A review on the mechanical quality of articular cartilage - implications for the diagnosis of osteoarthritis.

The functional behaviour of articular cartilage in diarthrodial joints is determined by its morphological and biomechanical properties. Whereas morphological changes are mainly detectable in the progressed stages of osteoarthritis, biomechanical properties seem to be more sensitive to early degenerative variations since they are determined by the biochemical composition and structural arrangement of the extracellular matrix. The objective of this paper is to review studies focussing on variations in the mechanical compressive properties during the early pre-osteoarthritic stage. The aim is to quantify the requirements to detect the early cartilage degeneration in pre-osteoarthritis based on the mechanical parameters and to create an updated basis for a better understanding of inherent relationships between characteristic parameters in articular cartilage. Correlations between mechanical and biochemical parameters as well as magnetic resonance, ultrasonic, histological and structural parameters were observed. In early osteoarthritis, static moduli decrease below 80% of healthy controls and dynamic moduli below 30% of controls. To identify osteoarthritic changes of articular cartilage based on static or dynamic mechanical parameters in an early stage of the disease progression the accuracy of a mechanical testing method has to be adequate to detect changes of 10% in cartilage stiffness.