Knee osteoarthritis

Despite knee osteoarthritis (OA) being an extremely common problem of ageing and a long-term consequence of many sports injuries, we still know relatively little about what causes it. People who have suffered complete rupture of the anterior cruciate ligament (ACL) are at particularly high risk of developing knee OA.

Research has shown that people with ACL-deficient knees undergo kinematic changes in the way they walk, affecting the tibiofemoral joint. We also know that similar kinematic changes show up in those who’ve had ACL reconstructions in their knees, suggesting that these people, too, may be at higher risk of developing OA.

Researchers from the United States recently looked more closely at the relationship between these altered knee mechanics and the way the cartilage responded after ACL injury. (Knee kinematics, cartilage morphology, and osteoarthritis after aCl injury. Medicine and Science in Sports and Exercise 2008: 40 (2) 215-222). Their review of available studies confirmed that ACL injury causes knee motion to change substantially, resulting in a shift in which regions of the cartilage are in contact.

This shift could cause increased loading in areas not conditioned for it, as well as reduced loading in other areas conditioned to cope with frequent load bearing. The findings from the research review suggest that cartilage regions are conditioned to their local mechanical environments and the kinematic shift observed after an ACL injury is likely to cause degenerative metabolic changes in some regions of cartilage if the tissue cannot adapt to the new loading pattern. These rapid changes result in fibrillation and other structural breakdown, initiating the onset of OA.

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