Knee osteoarthritis (OA), a disorder of cartilage and periarticular bone, is a public health problem without effective medical treatments. Some studies have suggested that vitamin D may protect against structural progression.
To determine if vitamin D supplementation reduces symptom and structural progression of knee OA
Design, Setting and Patients
The study was an NIH-funded, randomized, placebo-controlled, double-blind, clinical trial of 146 participants (mean age 62.4 (SD 8.5), 57 (61%) females, 115 (79%) whites) with symptomatic knee OA, performed at Tufts Medical Center between March 2006 – June 2009, testing a 2-year vitamin D intervention.
Participants were randomized to either placebo, or oral cholecalciferol 2000 IU daily with dose escalation to elevate serum levels to >36 ng/ml.
Main Outcome Measures
Primary outcomes were knee pain severity (WOMAC pain, 0–20, 0=no pain and 20=extreme pain), and cartilage volume loss measured by magnetic resonance imaging. Secondary endpoints included physical function, knee function (WOMAC function, 0–68, 0=no difficulty and 68=extreme difficulty), cartilage thickness, bone marrow lesions and radiographic joint space width.
Completion rate was 85%. Serum 25-hydroxyvitamin-D (25OHD) increased in the treatment arm (mean increase 16.1 ng/ml [95% CI, 13.7, 18.6]) vs. placebo (mean 2.1, [95% CI, 0.5, 3.7]), p<0.0001. Baseline knee pain was slightly worse in the treatment group (mean 6.9, [95% CI, 6.0, 7.7]) vs. placebo (mean 5.8, [95% CI, 5.0, 6.6], p=0.08). Baseline knee function was significantly worse in the treatment group (mean 22.7, [95% CI, 19.8, 25.6] than placebo (mean 18.5, [95% CI 15.8, 21.2], p=0.04). Knee pain decreased in both groups (vitamin D (mean, −2.3 [95% CI, −3.2, −1.4]); placebo mean (−1.5 [95% CI, −2.3, −0.6])) with no significant differences at any time point. Cartilage volume (%) decreased by the same extent in both groups (mean −4.3 [95% CI, −5.5, −3.1] vs. −4.3 [95% CI, −6.1, −2.4], p = 0.96). There were no differences in any of the secondary clinical endpoints.
Vitamin D supplementation for 2 years at a dose sufficient to elevate plasma levels of 250HD to > 36 ng/ml, when compared with placebo, did not reduce knee pain or cartilage volume loss in patients with symptomatic knee osteoarthritis.
The study was registered on ClinicalTrials.gov (NCT00306774).