Roos EM and Dahlberg L (2005) Positive effects of moderate exercise on glycosaminoglycan content in knee cartilage: a four-month, randomized, controlled trial in patients at risk of osteoarthritis. Arthritis Rheum 52: 3507–3514

Individuals with knee osteoarthritis often avoid exercise, in the belief that it might cause further degeneration of their joint cartilage. This belief conflicts with evidence from animal models of osteoarthritis that shows exercise has a protective effect. A Swedish study has shown in vivo improvements in cartilage quality, as assessed by delayed gadolinium-enhanced MRI, in individuals at risk of developing knee osteoarthritis who started to exercise regularly.

Roos and Dahlberg evaluated 30 patients aged 35–50 years who had undergone meniscectomy to treat a degenerative tear 3–5 years previously and who, therefore, were at high risk of developing knee osteoarthritis. Patients who self-reported moderate and low levels of exercise before the study were assigned to the exercise (n = 16) and no-intervention (n = 14) groups, respectively. Patients in the exercise group performed therapist-led, weight-bearing, strengthening exercises, on average three times a week, during the 4-month study period. MRI scans showed no difference in baseline glycosaminoglycan content of knee cartilage between the groups; however, similar scans taken after 4 months showed a statistically significant increase in the glycosaminoglycan content of knee cartilage in individuals in the exercise group (P = 0.036). Improvements in pain and knee function were also seen in the exercise group, although there were too few patients to detect statistically significant differences in clinical outcomes.

Increased glycosaminoglycan content of cartilage might improve its viscoelastic properties, say the authors, and could reduce susceptibility to osteoarthritis.