From wiki of MSM:

Osteoarthritis: After several reports that MSM helped arthritis in animal models, a double-blind, placebo-controlled study suggested that 1500 mg per day MSM (alone or in combination with glucosamine sulfate) was helpful in relieving symptoms of knee osteoarthritis[8] Kim et al. then conducted a double-blind clinical trial of MSM for treatment of patients with osteoarthritis of the knee. Twenty-five patients took 6 g/day MSM and 25 patients took a placebo for 12 weeks. Ten patients did not complete the study, and intention to treat analysis was performed. Patients who took MSM had significantly reduced pain and improved physical functioning, without major adverse events. No evidence of a more general anti-inflammatory effect was found, as there were no significant changes in two measures of systemic inflammation: C-reactive protein level and erythrocyte sedimentation rate. The authors cautioned that this short pilot study did not address the long-term safety and usefulness of MSM, but suggested that physicians should consider its use for certain osteoarthritis patients, and that long-term studies should be conducted.