To systematically review the evidence for association between serum 25-hydroxyvitamin D (25-(OH)D) and OA and the effect of vitamin D therapy on OA.
An English Medline, EMBASE and Cochrane Library search for vitamin D and OA from January 1980 to June 2012 was performed. Randomized controlled trials (RCTs), cohort, case-control and cross-sectional studies in adults were included. The methodological quality of the selected studies was assessed and a best-evidence synthesis was used to summarize the results due to the heterogeneity of the studies.
Of the 86 evaluated articles, 2 RCTs and 13 observational studies were included in the final analyses. The number of participants ranged from 64 to 1644 (0-100% women). The RCTs were only reported in abstract form and showed inconsistent results, most likely due to variations in their study design. There was insufficient or limited evidence for associations between 25-(OH)D and hand or hip OA. For knee radiographic OA as assessed by the Kellgren and Lawrence (KL) score, there was moderate evidence showing that low levels of 25-(OH)D were associated with increased progression of radiographic OA. Strong evidence for an association between 25-(OH)D and cartilage loss was apparent when joint space narrowing and changes in cartilage volume were considered collectively as cartilage loss.
25-(OH)D appears to be implicated in structural changes of knee OA rather than symptoms, and further well-designed RCTs are required to determine whether vitamin D supplementation can slow disease progression. There is insufficient evidence for other sites.