Clinical Question

Does vitamin D supplementation reduce knee pain in adults with osteoarthritis?

Bottom Line

Vitamin D supplementation at a dose targeted to reach a 25-hydroxyvitamin D plasma level greater than 36 ng per mL for two years did not reduce symptomatic knee pain in adults with osteoarthritis. (Level of Evidence = 1b)

Synopsis

Another trial of supplemental vitamin D not able to show any clinical benefit—when will this medical fad run its course? These investigators identified adults 45 years or older who met standardized international criteria for knee osteoarthritis based on clinical and radiology findings. Patients randomly received (concealed allocation assignment) 2,000 IU oral cholecalciferol or matched placebo daily, with optional subsequent increments of 2,000 IU at four, eight, and 12 months, targeted to reach a 25-hydroxyvitamin D plasma level between 36 and 100 ng per mL (89.9 and 249.6 nmol per L). No supplemental calcium was given, but all patients received advice on optimal dietary calcium intake. Individuals assessing outcomes using standard pain rating scales and magnetic resonance imaging remained masked to treatment group assignment. Complete follow-up occurred for 85% of participants at 24 months.

Using intention-to-treat analysis, significantly more patients assigned to the active supplement group achieved the target plasma level of 25-hydroxyvitamin D compared with the placebo group (61.3% vs. 8.3%, respectively). However, there was no significant difference in reduction of knee pain between the two treatment groups. There were also no significant between-group differences based on magnetic resonance imaging studies in cartilage thickness or bone marrow lesion size. At 16 months, significantly more patients in the supplemental group reported increased use of nonsteroidal anti-inflammatory drugs than in the placebo group (40% vs. 22%; number needed to treat = 5.6). The study was 80% powered to detect a predetermined clinically significant difference in pain reduction between the two treatment groups.

Reference

McAlindonTLaValleyMSchneiderEet alEffect of vitamin D supplementation on progression of knee pain and cartilage volume loss in patients with symptomatic osteoarthritis: a randomized controlled trial. JAMA.2013; 309( 2): 155– 162.

Study design: Randomized controlled trial (double-blinded)

Funding source: Government

Allocation: Concealed

Setting: Outpatient (any)