Original ResearchThe effect of vitamin D supplementation on knee osteoarthritis: A meta-analysis of randomized controlled trials

- Effects of vitamin D supplementation in the prevention of symptom and structural progression of knee OA were evaluated.
- A meta-analysis of four included RCTs was conducted to address the link between vitamin D and knee OA.
- Vitamin D supplementation was effective in improving the WOMAC pain and function in patients with knee OA.

ObjectiveWe conducted a meta-analysis of RCTs to evaluate the effects of vitamin D supplementation in the prevention of symptom and structural progression of knee OA.MethodsPubMed, Embase, and Web of Science databases were searched to identify relevant studies. Outcomes included Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain, function, stiffness, tibial cartilage volume, and serum vitamin D3 levels, and adverse events. Results were expressed as weight mean difference (WMD) with 95% confidence interval (CI), and risk ratio (RR) with 95%CI.ResultsFour RCTs involving 1136 patients were included in this study. Pooled estimates suggested that vitamin D supplementation was associated with a significant reduction in WOMAC pain, and WOMAC function, but not in WOMAC stiffness. Vitamin D supplementation increased the serum vitamin D3 level, but had no effect on tibial cartilage volume. Subgroup analysis showed that, a daily supplement of more than 2000 IU vitamin D significantly decreased the WOMAC pain and WOMAC function. There was no significant difference in incidence of adverse events between the vitamin D and placebo groups.ConclusionVitamin D supplementation was effective in improving the WOMAC pain and function in patients with knee OA. However, it had no beneficial effect on the prevention of tibial cartilage loss. Therefore, there is currently a lack of evidence to support the use of vitamin D supplementation in preventing the progression of knee OA.