Two RCTs (n=414) were included.
The studies scored 4 and 5 out of 5 on the Jadad scale. The drop-out rates in the two RCTs were high: 36% with glucosamine versus 33% with placebo and 46% with glucosamine versus 35% with placebo.
The risk of disease progression was significantly lower with glucosamine than with placebo; the pooled RR was 0.46 (95% CI: 0.28, 0.73, P=0.0011) and the pooled RD was 0.12 (95% CI: -0.05, -0.19, P=0.0006). No statistically significant heterogeneity was found (P>0.1). The NNT was 9 (95% CI: 6, 20).
In terms of symptoms, glucosamine significantly reduced pain (ES 0.41, 95% CI: 0.21, 0.60, P<0.0001) and significantly improved function (ES 0.46, 95% CI: 0.27, 0.66, P<0.0001) in comparison with placebo. No statistically significant heterogeneity was found for either meta-analysis (P>0.1).
Adverse effects were more common with glucosamine than placebo, but the difference was not statistically significant; the proportions of patients reporting any adverse effect were 94% with glucosamine versus 93% with placebo and 66% with glucosamine versus 64% with placebo. The most common adverse effects with glucosamine were abdominal pain, dyspepsia, diarrhoea, increased blood-pressure, fatigue and rash. The review did not report rates of these adverse effects.