Abstract
Damage to the articular cartilage is an exceedingly common problem affecting the joints of millions of people. When the injury does not penetrate the subchondral bone, the outcome of biological healing is poor and eventually leads to the degeneration of the articular surface. In young patients, small focal defects are often treated using marrow-stimulation techniques, including subchondral drilling (Tippet, 1996), microfracture (Tippet, 1996) and abrasion arthroplasty (Johnson, 1996). In these procedures, the torn or compromised cartilage is removed to expose the underlying bone and a rim of healthy cartilage is defined surrounding the defect hole. This is followed by drilling, puncturing or abrading the underlying bone to stimulate an inflammatory response and/or generate a blood clot within the defect. Clinical results suggest that the relative success of these procedures (i.e. the extent and quality of defect fill-in) depends on the level of strain experienced by the healing tissue during the early period following the procedure. Although the state of compressive and shear strain within and around the chondral defect is presumed to depend on the size and location of the defect, the relationship between these factors is not well documented. A finite element model of the medial compartment of the knee was constructed to examine the effect of defect size and location on predicted strains within and around the defect.
