Benefits of massive weight loss on symptoms, systemic inflammation and cartilage turnover in obese patients with knee osteoarthritis

Objective To investigate the effect of massive weight loss on (1) knee pain and disability, (2) lowgrade inflammation and metabolic status and (3) joint biomarkers in obese patients with knee osteoarthritis (OA). Methods 140 patients involved in a gastric surgery programme were screened for painful knee OA, and 44 were included (age 44 +/- 10.3 years, body mass index (BMI) 50.7 +/- 7.2 kg/m(2)). Clinical data and biological samples were collected before and 6 months after surgery. Results Before surgery, interleukin 6 (IL-6) levels were correlated with levels of high-sensitivity C reactive protein (hsCRP) (p=0.006) and Helix-II (p=0.01), a biomarker of cartilage turnover, and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) function score (p=0.03). Surgery resulted in substantial decrease in BMI (-20%). Levels of insulin and insulin resistance were decreased at 6 months. Knee pain decreased after surgery (24.5 +/- 21 mm vs 50 +/- 26.6 mm; p < 0.001), and scores on all WOMAC subscales were improved. Levels of IL-6 (p < 0.0001), hsCRP (p < 0.0001), orosomucoid (p < 0.0001) and fibrinogen (p=0.04) were decreased after surgery. Weight loss resulted in a significant increase in N-terminal propeptide of type IIA collagen levels (+32%; p=0.002), a biomarker of cartilage synthesis, and a significant decrease in cartilage oligomeric matrix protein (COMP) (-36%; p < 0.001), a biomarker of cartilage degradation. Changes in COMP concentration were correlated with changes in insulin levels (p=0.02) and insulin resistance (p=0.05). Conclusion Massive weight loss improves pain and function and decreases low-grade inflammation. Change in levels of joint biomarkers with weight loss suggests a structural effect on cartilage.