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 whether vitamin D supplementation reduces symptom and structural progression
of knee OA.
A 2-year randomized, placebo-controlled, double-blind, clinical trial involving 146
participants with symptomatic knee OA (mean age, 62.4 years [SD, 8.5]; 57 women [61%],
115 white race [79%]). Patients were enrolled at Tufts Medical Center in Boston between
March 2006 and June 2009.
Participants were randomized to receive either placebo or oral cholecalciferol, 2000
IU/d, with dose escalation to elevate serum levels to more than 36 ng/mL.
Primary outcomes were knee pain severity (Western Ontario and McMaster Universities
[WOMAC] pain scale, 0-20: 0, no pain; 20, extreme pain), and cartilage volume loss
measured by magnetic resonance imaging. Secondary end points included physical function,
knee function (WOMAC function scale, 0-68: 0, no difficulty; 68, extreme difficulty),
cartilage thickness, bone marrow lesions, and radiographic joint space width.
Eighty-five percent of the participants completed the study. Serum 25-hydroxyvitamin
D levels increased by a mean 16.1 ng/mL (95% CI, 13.7 to 18.6) in the treatment group
and by a mean 2.1 mg/mL (95% CI, 0.5 to 3.7) (P < .001) in the placebo group. Baseline
knee pain was slightly worse in the treatment group (mean, 6.9; 95% CI, 6.0 to 7.7)
than in the placebo group (mean, 5.8; 95% CI, 5.0 to 6.6) (P = .08). Baseline knee
function was significantly worse in the treatment group (mean, 22.7; 95% CI, 19.8
to 25.6) than in the placebo group (mean, 18.5; 95% CI, 15.8 to 21.2) (P = .04). Knee
pain decreased in both groups by a mean -2.31 (95% CI, -3.24 to -1.38) in the treatment
group and -1.46 (95% CI, -2.33 to -0.60) in the placebo group, with no significant
differences at any time. The percentage of cartilage volume decreased by the same
extent in both groups (mean, -4.30; 95% CI, -5.48 to -3.12 vs mean, -4.25; 95% CI,
-6.12 to -2.39) (P = .96). There were no differences in any of the secondary clinical
end points.
Vitamin D supplementation for 2 years at a dose sufficient to elevate 25-hydroxyvitamin
D plasma levels to higher than 36 ng/mL, when compared with placebo, did not reduce
knee pain or cartilage volume loss in patients with symptomatic knee OA.
clinicaltrials.gov Identifier: NCT00306774.