Low Vitamin D Levels May Worsen Knee Pain of People with Osteoarthritis

13/11/07 Low vitamin D levels may cause greater knee pain and difficulty walking in patients with knee osteoarthritis, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Boston, Mass.

Knee osteoarthritis is caused by cartilage breakdown in the knee joint. Factors that increase the risk of knee osteoarthritis include being overweight, age, injury or stress to the joints, and family history can increase the risk of knee osteoarthritis.

Recent studies have shown that vitamin D influences both musculoskeletal and neuromuscular function. Taking a closer look at this, in a two-year trial of vitamin D supplements on knee osteoarthritis progression, researchers tested whether vitamin D deficiency at study entry is associated with pain and physical function in OA patients. Researchers studied 65 women and 35 men in their sixties who showed signs of having knee OA by measuring blood levels of vitamin D, their baseline knee pain, the time needed for arising several times from a chair, and the time needed to walk 20 meters.

Of the 100 participants, 47 percent were vitamin D deficient, with vitamin D levels below 30 ng/ml. This deficiency contributed to increased pain and difficulty walking among the participants. However, the deficiency did not affect time need to stand and sit repeatedly.

Vitamin D promotes the absorption of calcium and phosphorus needed for bone mineralization, growth and repair. Sources of vitamin D are available to a lesser extent from dietary sources typically found in fortified margarine, oily fish, liver, fortified breakfast cereals and dairy products. Sun exposure helps vitamin D to become active.

Absorption of vitamin D from food and conversion of it to the active form is less efficient in elderly persons. For this reason, vitamin D supplements of 400-800 and calcium doses of 1,200 to 1,500 mg a day are recommended to prevent osteoporosis. The results of this study suggest that Vitamin D supplements may also help in arthritis treatment.

"These preliminary results suggest that, among people with knee osteoarthritis, having a low vitamin D level is associated with more knee pan and greater functional limitation," said Tim McAlindon, MD, MPH; associate professor of medicine, division of rheumatology, Tufts New England Medical Center; and an investigator in the study. "Future results from this ongoing randomized, double-blinded, placebo-controlled clinical trial of vitamin D will help determine whether vitamin D is an effective disease-modifying intervention for knee osteoarthritis."