Vitamin D No Help for Arthritic Knees

by | Jan 18, 2013

Vitamin D supplements had no impact on the pain of knee osteoarthritis (OA), researchers reported.

In a randomized, placebo-controlled trial, serum 25-hydroxy vitamin D supplements also had no effect on disease progression in patients with symptomatic knee OA, according to Timothy McAlindon, DM, of Tufts Medical Center in Boston, and colleagues.

The 2-year trial contradicts observational studies that had suggested higher levels of vitamin D might slow the progression of the disease, McAlindon and colleagues reported in the Jan. 9 issue of the Journal of the American Medical Association.

Knee OA has “significant functional impact and has considerable societal costs through work loss, early retirement, and arthroplasty,” the researchers noted.

Despite that, no medical treatments are available that alter the course of the disease, they added.

The notion that vitamin D might help was based on its role in bone health, combined with the importance of bone changes in OA and epidemiologic observations that hinted at slower disease progression among patients with higher vitamin D levels, the authors said.

They studied 146 people with symptomatic knee OA, enrolled at Tufts between March 2006 and June 2009, and randomly assigned to receive oral cholecalciferol or placebo. The initial dose was 2,000 IU/day, with dose escalation, if needed, to achieve a serum level of more than 36 ng/mL.

To maintain blinding when dose escalation was deemed necessary, the study statistician selected a placebo patient for a matched change in dose.

The primary outcomes of the study were knee pain severity, as measured on the Western Ontario and McMaster Universities pain scale and loss of cartilage as measured by MRI.

The researchers found that overall, 61.3% of patients in the treatment group reached the target of 36 ng/mL by the end of the study, with an average increase of 16.1 ng/mL.

In contrast, 8.3% of those in the placebo group reached the target, with an average increase of 2.1 ng/mL over the study period.

Knee pain at baseline was 6.9 on the 21-point pain scale for those in the treatment group, which was slightly worse than the 5.8 in the placebo group.

Baseline knee function was significantly worse (P=0.04) in the treatment group than in the placebo group.

While knee pain decreased in both groups, dropping by an average of 2.31 points in the treatment group and 1.46 in the placebo group, but the differences were not statistically significant ( P=0.17)

Similarly, the percentage of cartilage volume fell by 4.3% and 4.25% in the treatment and placebo groups, but the difference was not statistically significant (P=0.96)

McAlindon and colleagues cautioned that the loss of cartilage volume was lower than expected, which might have made it more difficult to see a positive result.

They also pointed out that the patient population was chosen for “fairly severe structural damage” in an attempt to make sure that results would apply to patients whose disease had the greatest impact.

But it is possible that the therapeutic intervention was simply futile in patients with relatively advanced disease, they said.

One of the main limitations of the study was the focus on vitamin D, which is essential for bone health but less so for maintenance of healthy cartilage, commented Joseph Guettler, MD, of Beaumont Health System in Royal Oak, Mich.

“When it comes to articular cartilage, we might have been barking up the wrong tree here,” Guettler told MedPage Today in a video interview. “I think future study needs to focus on components of healthy articular cartilage, such as glucosamine-chondroitin [and] hyaluronic acid derivatives that are known to lubricate and nourish healthy joints.”

From: Medpage Today

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