ACR 2010: No Benefit from Vitamin D in Knee Osteoarthritis

Researchers report disappointing study results showing that vitamin D supplementation has no effect on slowing the progression of knee osteoarthritis.

There has been a lot of buzz around vitamin D lately in a number of diseases, including arthritic disease. But vitamin D supplementation had no effect on slowing the symptoms or the progression of knee osteoarthritis (OA), according to an NIH-funded, double-blind, placebo-controlled trial presented at the 2010 Annual Scientific Sessions of the American College of Rheumatology.

The investigators of this study were disappointed in results of this first randomized controlled trial of vitamin D in knee OA. “Bone health may determine where OA progresses, and earlier studies suggested that vitamin D might be of benefit in knee OA,” said lead author Timothy E. McAlindon, MD, Tufts Medical Center, Boston, MA.

“There are several possible explanations for the negative results. Perhaps our study patients had more severe OA than those in previous trials suggesting a benefit for vitamin D supplementation, or maybe two years of treatment was not long enough and maybe higher doses of vitamin D than we used are needed,” he continued.

McAlindon said that future plans include pooling data from this trial with data from two other ongoing trials of vitamin D performing a meta-analysis to determine if there are subsets of patients with knee OA who can benefit from vitamin D supplementation. “This is the prudent thing to do before embarking on another clinical trial,” he said.

The two-year study screened 282 patients with symptomatic knee OA according to ACR criteria. Of these, 146 were randomized to daily vitamin D3 supplementation (initially 2000 IU/day, but could be escalated in increments of 2000 IU as needed to reach a target serum vitamin D level of >30 ng/mL) or placebo. The dummy dose of placebo was escalated as needed. Randomization was stratified for disease severity according to the Kellgren Lawrence grade.

The groups were well balanced for demographic and disease characteristics. Mean age was 62 years, 57% were female, 79% were Caucasian, mean Body Mass Index was 30.7 kgm. At baseline, mean serum vitamin D level was 22.3 ng/ml. At the end of the treatment period, mean serum vitamin D level was 89 ng/ml.

The study was completed by 124 patients (85%). No significant differences were seen between the two groups for pain and for functional ability. A slight reduction in pain was seen in the vitamin D group, but this was variable he said. Functional scores were similar between groups.

Looking at measures of cartilage deterioration and bone marrow lesions, both groups had identical cartilage loss and identical joint space width following treatment. Slightly more side effects were reported in the vitamin D group, including endocrine, genitourinal, and systemic side effects, but McAlindon said that these effects were unrelated to vitamin D supplementation.