02.06.09

Low levels of vitamin D are associated with the loss of cartilage in the knee joint of older individuals, researchers in Australia report.

"Cartilage loss is the hallmark of osteoarthritis," Dr. Changhai Ding told Reuters Health. By the time patients reach the point of needing knee replacement, 60 percent of cartilage has been lost, he said.

However, "achieving vitamin D sufficiency in osteoarthritis patients could significantly delay total knee replacement," said Ding, at the Menzies Research Institute in Tasmania. In a study, Ding and colleagues found "osteoarthritis patients with vitamin D sufficiency have approximately 1.5 percent less loss of knee cartilage per year than patients with vitamin D deficiency," said Ding.

The investigators measured levels of vitamin D in blood samples and knee cartilage volume on X-rays from 880 men and women who were 51 to 79 years old. The team then took similar measurements again almost 3 years later among 353 of the study participants, the researchers report in the journal Arthritis & Rheumatism.

Overall, 58 percent of these subjects showed changes in knee cartilage indicating worsening osteoarthritis between the first and second measurements, and half reported knee pain.

Both at the beginning of the study enrolment and at follow up, men and women with vitamin D deficiency had lower knee cartilage volume and were more likely to experience knee pain. Ding's team concludes that vitamin D plays an important role in cartilage changes, and that vitamin D deficiency may predict knee cartilage loss over time.

The researchers call for further research to see if vitamin D supplementation can delay the progression of knee osteoarthritis and the need for total knee replacement in osteoarthritis patients.

SOURCE: Arthritis & Rheumatism, May 2009

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