In people suffering from knee osteoarthritis, supplementation of vitamin D is associated with improvement in WOMAC pain and functional improvement, as deduced from a systematic review and meta-analysis conducted by Zi-Xia Zhao et al. Researchers aimed to yield evidence on the efficacy of vitamin D supplementation for clinical prevention and management of knee osteoarthritis.

For finding relevant studies, databases like SinoMed, Web of Science, China National Knowledge Infrastructure, PubMed, Wanfang, China Biological Medicine Database, and Embase were searched. For the meta-analysis, RevMan5.3 software was utilized. The findings of the study were expressed as standardized mean difference (SMD) with 95% confidence interval (CI) or weighted mean difference with 95% CI.

The study included 6 randomized controlled trials and 1599 participants having knee osteoarthritis. Supplementation with vitamin D was found to be statistically significant for Western Ontario and McMaster Universities Arthritis Index (WOMAC) score (SMD = - 0.67) in knee osteoarthritis people, including  stiffness score (SMD = - 0.13), WOMAC pain score (SMD = - 0.32), and function score (SMD = - 0.34). In the subgroup assessment, vitamin D supplementation less than 2000 international units (IU) was statistically significant for the decline in stiffness score (SMD = - 0.22).

Supplementation with vitamin D is associated with a reduction in synovial fluid volume advancement in people having knee osteoarthritis (SMD = - 0.20). Regarding improvement in bone marrow lesions (SMD = 0.03), tibia cartilage volume (SMD = 0.12), and joint space width (SMD = - 0.10), no statistical significance was noted. However, there is a paucity of strong evidence that vitamin D supplements can aid in the prevention of structural advancement in knee osteoarthritis.