Osteoarthritis (OA) of the knee affects approximately 20 million Americans. It is characterized by pain, stiffness, and sometimes swelling due to inflammation and fluid accumulation.
Knee osteoarthritis is caused by cartilage deterioration within the knee joint. Factors that increase the risk of knee osteoarthritis include being obesity, age, injury or stress to the joints. In addition genetic factors play a role since a family history of the disorder can increase the risk of developing knee osteoarthritis.
A new study has shed light on another possible risk factor for OA of the knee. Low vitamin D levels may cause greater knee pain and difficulty walking in patients with knee osteoarthritis, according to research presented recently at the American College of Rheumatology Annual Scientific Meeting in Boston, Mass held November 6-12, 2007.
Recent studies have shown that vitamin D has significant influence on proper function of the musculoskeletal and neuromuscular systems.
In a two-year trial of vitamin D supplements and their effect on progression of knee OA, researchers tested whether vitamin D deficiency at study entry was linked to 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 getting up out of a chair into a standing position and then back down again repetitively, 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 needed to stand and to sit repeatedly.
Vitamin D helps the absorption of calcium and phosphorus needed for bone mineralization, modeling, growth and repair. Sources of vitamin D are available in certain food sources such as 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 occurs less efficiently 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 interesting finding from this study suggests that Vitamin D supplements may also help in arthritis treatment as well.
Tim McAlindon, MD, MPH, associate professor of medicine, division of rheumatology, Tufts New England Medical Center and an investigator in the study commented, “These … results suggest that…people with knee osteoarthritis, having a low vitamin D level is associated with more knee pain and greater functional limitation. Dr.McAlindon also added, “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.”
Currently, treatment of osteoarthritis of the knee is limited to a combination of weight control, exercise, non-steroidal anti-inflammatory drugs, local treatments (ice, heat, topical agents), glucocorticoid injections, viscosupplements (lubricants injected into the knee), arthroscopic procedures (cleaning the knee out using a small telescope), and knee replacement in patients with severe OA.
The “holy grail” is to develop drugs that help slow down cartilage loss and possibly even help cartilage regenerate. While this study does not prove that vitamin D does any of this, it is a ray of hope that someday, researchers will be able to discover disease modifying osteoarthritis drugs.