MECHANICAL-PROPERTIES OF ARTICULAR-CARTILAGE IN KNEES WITH UNICOMPARTMENTAL OSTEOARTHRITIS

We studied the mechanical properties of cartilage from the apparently unaffected compartment of knees with unicompartmental osteoarthritis ( OA). Plugs of cartilage and subchondral bone, 8 mm in diameter, were o btained from the tibial plateau of seven patients treated by total kne e replacement. Control specimens were obtained from eight cadaver knee s of similar age. Specimens were loaded by a plane-ended indentor in a hydraulic materials testing machine; we measured thickness, 'softness ', rate of creep, and compressive strength of the articular cartilage. We found that the 'unaffected' cartilage from OA knees was significan tly thinner and softer than control cartilage, and it was slightly, al though not significantly, weaker. We conclude that the apparently unaf fected cartilage in knees with unicompartmental OA is mechanically inf erior to normal cartilage, even although clinically, radiologically an d morphologically it appears to be sound.