Knee osteoarthritis does not benefit from vitamin D supplementation

By Will Boggs MD

NEW YORK (Reuters Health) - Vitamin D supplementation does not improve tibial cartilage volume or reduce knee pain in patients with knee osteoarthritis, researchers from Australia report.

"In post-hoc analyses, vitamin D supplementation significantly reduced (magnetic resonance imaging) MRI-assessed knee joint effusion (which indicated inflammation) in patients with knee osteoarthritis," Dr. Changhai Ding, from the University of Tasmania, Hobart, Tasmania, Australia, told Reuters Health by email. "These suggest that further studies with different outcome measures are required to determine the effects of vitamin D supplementation on knee osteoarthritis."

In epidemiological studies, low serum 25-hydroxyvitamin D levels have been associated with greater knee pain, a higher prevalence of radiographic knee osteoarthritis, and higher risk of progression, but randomized controlled trials of vitamin D supplementation in patients with knee osteoarthritis have yielded contradictory results.

In the Vitamin D Effect on Osteoarthritis (VIDEO) study, Dr. Ding and colleagues evaluated the effects of two years of vitamin D supplementation (50,000 IU of vitamin D3 monthly) versus placebo on knee pain and knee cartilage volume in 413 patients with symptomatic knee osteoarthritis and low 25-hydroxyvitamin D levels.

The mean serum 25-hydroxyvitamin D level increased by 40.6 nmol/L in the vitamin D group and by 6.7 nmol/L in the placebo group over two years. More patients in the vitamin D group (79%) than in the placebo group (43%) achieved 25-hydroxyvitamin D levels above 60 nmol/L at month 3.

This difference in achieved vitamin D levels did not translate into significant differences between the groups in Western Ontario and McMaster University Index of osteoarthritis (WOMAC) pain scores, which improved to a similar extent with vitamin D and with placebo.

Tibial volume at 24 months, the other primary endpoint, did not differ between the vitamin D and placebo groups, according to the March 8 report in JAMA.

In post-hoc analyses, patients in the vitamin D group had significant improvements in visual analog scale knee pain (compared with the placebo group), and there were significantly more patients in the vitamin D group (35%) than in the placebo group (25%) who showed at least 50% improvements in WOMAC pain scores.

"The results from the randomized clinical trial suggest that vitamin D supplementation does not have major effects on tibial cartilage loss and WOMAC knee pain in patients with knee osteoarthritis, but may have modest effects on other outcomes such as physical function and joint effusion," Dr. Ding concluded.

The Australian National Health and Medical Research Council supported this research. Four coauthors reported disclosures.

SOURCE: http://bit.ly/1QEm0fc

JAMA 2016.

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