Vitamin D to Slow Progression of Knee Osteoarthritis

Symptomatic knee OA is one of the most frequent causes of limitation in lower limb tasks, especially in the elderly. Knee OA causes 68 million lost work days per year. OA is the most frequent reason for joint replacement, at a cost of billions of dollars per year. There are currently no completely effective medical remedies for OA. Pharmaceutical companies are trying to develop drugs that will slow the disease progression of OA; however, such medications will be expensive to use in a population in which OA is common. There is evidence that vitamin D supplementation, a simple and much cheaper intervention, may prove useful in slowing the progression of OA. Even if only modestly effective, it could have considerable impact in terms of reducing the societal burden of OA. Therefore, in the interests of public health, the efficacy of vitamin D supplementation as a disease-modifying treatment for OA needs to be tested in a rigorous clinical trial. Disease modification trials for knee OA have been difficult in the past due to limitations of radiographic techniques. Fortunately, magnetic resonance imaging (MRI) has emerged as a valid, precise, and reproducible tool for the measurement of damage of cartilage and joint structures. The purpose of this study is to evaluate the effects of vitamin D on knee OA symptoms and physical function in older adults. Patients with symptomatic knee OA will be randomly assigned to receive vitamin D at 2,000 International Units (IU) a day or placebo. Each participant will be in the study for about 2 years. During that time, there will be 9 scheduled study visits (screening, Months 0, 2, 4, 8, 12, 16, 20, and 24) and interim safety visits as needed. Measurements of vital signs, a knee exam, blood and urine collection, pill counts, and completion of questionnaires will occur at all visits. Participants' physical function will be assessed at study entry and Months 0, 12, and 24. MRI, bone density scanning, and an assessment by the study staff will occur at Months 0, 12, and 24. Knee x-rays will occur at study screening and Month 24.