BOSTON, Massachusetts—Vitamin D-deficient knee osteoarthritis (OA) patients are more likely to have higher levels of pain and three times more likely to report difficulty walking, compared to their counterparts with higher blood levels of this vitamin, according to research presented at the American College of Rheumatology annual scientific meeting in Boston.1 Low levels of vitamin D did not affect performance on the chair test, the study showed.

"This adds further data to the body of evidence that vitamin D has important benefits for musculoskeletal function."—Tim McAlindon, MD, MPH.
"This adds further data to the body of evidence that vitamin D has important benefits for musculoskeletal function," said study presenter Tim McAlindon, MD, MPH, associate professor of medicine in the division of rheumatology at Tufts New England Medical Center in Boston.

Nearly half of patients were vitamin D deficient

In the 2-year trial, researchers tested whether vitamin D deficiency at study entry was associated with pain and physical function among 65 women and 35 men with OA who were in their 60s. Researchers assessed blood levels of vitamin D, baseline knee pain using the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index, the timed chair stand and 20-meter walking tests.

Of the 100 participants, 47% were vitamin D deficient with serum 25(OH)D <30 ng/mL 30 ng/mL. Overall, study participants had a mean pain score of 6.7 (SD 3.8), mean 20-meter walking time of 17.4 seconds (SD 5.2), and mean chair stand test time of 21.4 seconds (SD 7.8). Vitamin D deficiency was associated with greater knee pain (adjusted OR for WOMAC pain score >6, 3.22, 95% CI, 1.08-9.58), the researchers report.

Deficiency associated with more pain, slower walking

Vitamin D deficiency was associated with a slower walking speed (adjusted OR, 3.24, 95% CI, 1.12-9.42). The association with 25(OH)D was slightly reduced by inclusion of knee pain severity in the model (adjusted OR, 2.94, 95% CI, 0.91-9.44), the researchers point out. Vitamin D deficiency was not associated with chair stand time (adjusted OR, 0.92, 95% CI, 0.29-2.92).

"Vitamin D deficiency is common in elders and there are many reasons for elders to get their levels checked and take supplements if low," David T. Felson, MD, MPH, professor of medicine and epidemiology and chief of the clinical epidemiology unit at the Boston University School of Medicine in Massachusetts, told MSKreport.com. "It is not yet clear whether osteoarthritic pain is one of these."
 
Reference

1. Wang J, Nuitte M. Wheeler LM, et al. Low vitamin D levels are associated with greater pain and slow walking speed in patients with knee osteoarthritis (KOA). Presented at: American College of Rheumatology Meeting; November 6-11, 2007; Boston, Mass. Presentation. No. 199.