I would like to reply to the recent letter by Murphy et al1 regarding the possible influence of obesity and weight changes on the results of the Strontium ranelate Efficacy in Knee Osteoarthritis trIAl (SEKOIA) trial of the efficacy and safety of strontium ranelate in knee osteoarthritis.2 Obesity and overweight are recognised risk factors for osteoarthritis,3 and so it is essential to include such patients in studies of potential treatments, since they are likely to constitute a substantial proportion of the patients who could hope to benefit from treatment. Almost half of the patients in SEKOIA were obese at baseline (44% had body mass index (BMI) ≥30 kg/m²) with no relevant differences between the three treatment groups: 45% for the patients receiving strontium ranelate 1 g/day; 43% for strontium ranelate 2 g/day; and 44% for placebo. There was no significant variation in body weight over the 3 years of the trial in any of the treatment groups (mean changes were +0.20±4.42, +0.22±4.84 and −0.46±6.35 kg, respectively) and adjustment of the main study results for obesity did not produce substantial changes in the results on joint space narrowing (JSN) with strontium ranelate (treatment-placebo difference in JSN (mm) adjusted for obesity: E(SE) 0.10 (0.04), 95% CI 0.02 to 0.19, p=0.016 for 2 g/day; treatment-placebo difference in JSN (mm)not adjusted for obesity: E(SE) 0.10 (0.04), 95% CI 0.02 to 0.19, p=0.018 for 2 g/day). Moreover, to ascertain the absence of a relationship between weight and joint space width (JSW) changes, JSN was evaluated according to quartiles of weight change, independently of treatment group, and the results did not show any obvious relationship (change in JSW in the lowest quartile (weight loss <2 kg): −0.33±0.68, change in JSW in the highest quartile (weight gain >2.3 kg): −0.30±0.53 mm, respectively). No studies have been conducted to date to assess the efficacy of strontium ranelate combined with weight reduction; and there are no such data available in SEKOIA. However, I agree that weight control, reduction when needed and exercise are essential components of the management strategy of patients with knee osteoarthritis and could be associated with strontium ranelate treatment.