Osteoarthritis (OA) is an age-related degenerative condition of joints, which mainly involves cartilage, joint lining, ligaments, muscle, and underlying bone. The most commonly affected joint is knee joint, which can lead to disability in the elderly. Knee OA usually results due to the deficiency of vitamin D. However, data regarding the efficacy of vitamin D supplementation in knee osteoarthritis are contradictory.

A group of investigators conducted a systematic literature review to find out the outcomes of vitamin D supplementation in managing knee osteoarthritis. The electronic literature searches of studies from inception to 6th July 2016 was performed in databases like PubMed, Embase, and Cochrane CENTRAL. Cochrane risk of bias tool was adopted to check the quality of included Randomized Controlled Trials (RCTs). The primary outcome measures were changes in Western Ontario and McMaster Universities (WOMAC) index, Visual Analog Scale (VAS) and Functional Pain Score (FPS). Secondary outcomes included changes in tibial cartilage thickness, joint space width, and safety profile. Participants were divided randomly either to the treatment or placebo group. Participants were provided cholecalciferol [dose range of 800–60,000 IU] as an intervention using the oral route, with an exception in the one study where participants were given Ergocalciferol.

The remarkable increase was observed in the serum level of Vitamin D among the treatment group as compared to the placebo group. No notable reduction in pain and function was reported on WOMAC scale except in one study. There was no considerable difference noticed in WOMAC stiffness in any study. VAS assessment was done in three studies, where two showed statistically significant improvement in knee pain.

Safety data was reported in 3 RCTs, and a single incidence of calculus ureteric and hip fracture was found to be linked to the drug. Evidence obtained from RCTs are not sufficient enough to support the use of vitamin D supplementation in patients suffering from knee osteoarthritis.