Abstract
Objectives:
This study aims to determine whether vitamin D supplementation or maintaining sufficient vitamin D level reduces foot pain over two years in patients with symptomatic knee OA.
Methods:
A post hoc study was conducted from a randomized double-blind placebo-controlled trial named the VItamin D Effect on Osteoarthritis (VIDEO) study. Symptomatic knee OA patients with serum 25-hydroxyvitamin D levels between 12.5 nmol/L to 60 nmol/L were included and randomly allocated to either monthly vitamin D3 or placebo treatment (1:1) for 2 years. Manchester Foot Pain and Disability Index (MFPDI) was used to evaluate foot pain and Disabling foot pain was defined as at least one of the 10 functional limitation items (items 1-9,11) being documented as on 'most/every day(s)' in the last month. A repeated-measure mixed effect model was used to analyze the change of MFPDI scores between groups adjusting for potential confounders.
Results:
A total of 413 patients with a mean age of 63.2 years (49.7% males) were enrolled and 340 completed the study. The mean MFPDI score was 22.8±7.3, with 23.7% participants having disabling foot pain at baseline. There were significant differences in MFPDI scores change between groups over 2 years, with more improvements in vitamin D group than in placebo group (-0.03 vs. 1.30, P=0.013) and more improvement in those maintaining sufficient vitamin D levels (n=226) than those who did not (n=114) (-0.09 vs. 2.19, P=0.001).
Conclusion:
Vitamin D supplementation and maintenance of sufficient vitamin D levels may improve foot pain in those with knee OA.
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