Maintaining sufficient serum vitamin d levels over two years is associated with improved knee structural and symptomatic outcomes in people with knee osteoarthritis: a post hoc analysis of the video trial
S. Zheng Osteoarthritis and Cartilage VOLUME 25, SUPPLEMENT 1, S180-S181, APRIL 01, 2017
Purpose: The evidence of whether vitamin D supplementation is an effect treatment for osteoarthritis (OA) is contradictory. In the Vitamin D Effect on Osteoarthritis (VIDEO) randomised controlled trial (RCT), a high proportion of participants achieving sufficient 25-hydroxyvitamin D [25(OH)D] level during the trial in the placebo group may masked the beneficial effects of vitamin D supplementation. This study aims to describe whether maintaining sufficient serum vitamin D levels in people with knee OA and baseline vitamin D insufficiency has an association with change in knee structures and symptoms over two years in a post-hoc analysis of VIDEO.
Methods: Participants (n=413, age 63.2 years) with symptomatic knee OA and vitamin D insufficiency were enrolled in a clinical trial. 340 participants (82.3%) completed the study with 25(OH)D measurements at month 0, 3 and 24. Participants were classified as consistently insufficient [serum 25(OH)D≤50nmol/l at month 3 and 24, n=45], fluctuating [25(OH)D>50nmol/l at either point, n=68] and consistently sufficient [25(OH)D>50nmol/l at month 3 and 24, n=226] vitamin D groups. Knee cartilage volume, cartilage defects, bone marrow lesions (BMLs) and effusion-synovitis volume were assessed using MRI at baseline and month 24. Knee symptoms were assessed at baseline, month 3, 6 12 and 24 using Western Ontario and McMaster Universities Arthritis Index (WOMAC).
Results: The consistently sufficient group had significantly less loss of tibial cartilage volume (β: 2.1%, 95% CI: 0.3%, 3.9%), less increase in effusion-synovitis volume (β: -2.5ml, 95% CI: -4.7, -0.2) and less loss of WOMAC physical function (β: -94.2, 95% CI: -183.8, -4.5) compared to the consistently insufficient group in multivariable analyses. In contrast, there were no significant differences in these outcomes between the fluctuating and consistently insufficient groups. Changes in tibiofemoral cartilage defects, BMLs and knee pain were similar between groups.
Conclusions: This post hoc analysis suggests beneficial effects of maintaining vitamin D sufficiency on cartilage loss, effusion-synovitis and physical function in people with symptomatic knee OA.