Meta-analysis of the related nutritional supplements dimethyl sulfoxide and methylsulfonylmethane in the treatment of osteoarthritis of the knee

Brien S, Prescott P, Lewith G · Evidence-Based Complementary and Alternative Medicine

Fixed-effects pooling gave a 6.34 mm reduction on a 100 mm pain scale (95% CI 2.41 to 10.27), statistically significant but under the 9 to 12 mm the authors take as clinically relevant; with heterogeneity across the three trials (chi-squared 6.28, P=0.043) the random-effects estimate was the same 6.34 mm with a wider interval (SE 3.49, 95% CI -0.49 to 13.17) and not significant, and the overall effect size of 1.82 was neither statistically nor clinically significant. The two DMSO trials were topical gels; the one oral MSM trial (Kim 2006, 12 weeks, 21 against 19 analysed) was itself positive on WOMAC pain (-14.6 against -7.3, P=0.041). The authors' conclusion: 'Current evidence suggests DMSO and MSM are not clinically effective in the reduction of pain in the treatment of OA.'

Population

Three randomized controlled trials in knee osteoarthritis — two of DMSO, one of MSM

Intervention

Dimethyl sulfoxide or methylsulfonylmethane

Comparator

Placebo or control

Limitations

Only three trials met inclusion and only one tested MSM, so this is weak evidence against MSM specifically rather than a decisive refutation; the funnel plot was asymmetric on the strength of the one null trial. The authors judge all three trials methodologically sound but under-dosed by current recommendations and, for the two DMSO trials, too short, and say no definitive conclusions can be drawn. The paper gives the MSM trial's dose as 3 g/day in one table and 3 g twice daily in another. Funded by the Southampton Complementary Medicine Charitable Research Trust and the Rufford Maurice Laing Foundation; University of Southampton authors.