A new study that will be published in the American Journal of Medicine supports the hypothesis that maintaining healthy vitamin D levels may slow the progression of knee osteoarthritis.
Osteoarthritis, also known as wear and tear arthritis, develops when the cartilage between joints deteriorates. When this occurs, the bones of joints rub more closely against one another, resulting in pain and swelling.
More than 27 million people in the U.S. are affected by osteoarthritis, with the knee being one of the most commonly affected joints.
Knee osteoarthritis is typically progressive and irreversible, leaving treatment methods to focus on management of symptoms rather than curing the condition. Physical therapy and exercise often play an integral role in the management of knee osteoarthritis as these methods help prevent further cartilage loss.
Some medications and injections are used to relieve pain; however, these are often accompanied by unwanted side effects. The last option available for knee osteoarthritis patients is surgery. In fact, the majority of people with knee osteoarthritis require surgery.
Due to the limited treatment options available for patients with knee osteoarthritis, researchers have prioritized finding treatment methods that have less side effects and are less invasive. In recent years, researchers have begun studying vitamin D supplementation as treatment for patients with knee osteoarthritis. However, studies have produced conflicting results.
A clinical trial from 2013 found that vitamin D supplementation successfully slowed the progression of knee osteoarthritis. This study consisted of 103 patients who were randomized to receive vitamin D or placebo. The vitamin D group received 60,000 IU of vitamin D for 10 straight days at baseline, and then 60,000 IU once a month for a year. The placebo group received a placebo pill for 10 straight days, then a placebo pill every month for a year. Pain increased in the placebo group, but decreased in the vitamin D group. Furthermore, those who received vitamin D showed improvement in physical function; whereas, the placebo did not. However, not all clinical trials presented promising results.
In 2016, a clinical trial found that vitamin D supplementation did not reduce pain or slow the progression of knee osteoarthritis. However, this study did not use daily dosing. Instead, they used a monthly supplement of 50,000 IU, and participants from both groups achieved vitamin D sufficiency (> 20 ng/ml). In fact, 62% of participants in the placebo group became vitamin D sufficient. Why is this a problem? The high proportion of participants who became vitamin D sufficient in the placebo group may have masked the benefits of vitamin D supplementation.
Therefore, the researchers from the same study decided to conduct a new analysis. This time, the researchers compared the progression of knee osteoarthritis in the participants who maintained vitamin D sufficiency to those who remained vitamin D deficient.
A total of 340 participants with knee osteoarthritis completed the study, all of whom were considered vitamin D insufficient (vitamin D status < 20 ng/ml) at the beginning of the study. Vitamin D levels were measured at 0, 3 and 24 months into the study.
The researchers divided the participants based upon whether they achieved vitamin D sufficiency, remained insufficient or fluctuated between insufficient and sufficient during the study. A total of 45 participants continued to have low vitamin D levels throughout the study, 65 participants’ vitamin D levels fluctuated between sufficient and insufficient and 226 participants were consistently vitamin D sufficient from 3 to 24 months.
The researchers discovered that those who were consistently vitamin D sufficient showed signs of delayed progression, including significantly less loss of cartilage and significantly less loss of physical function, compared to those who remained insufficient throughout the study.
The study noted that there were no significant differences in the progression of knee osteoarthritis between those with fluctuating sufficiency and those who were consistently insufficient.
The researchers summarized their findings,
“Overall, our results suggest that maintaining sufficient serum vitamin D may have a small but 4 beneficial effect on retarding cartilage loss, reducing joint inflammation and improving physical function in knee osteoarthritis patients.”
Tovey, A. & Cannell, JJ. Maintaining healthy vitamin D levels may help patients with knee osteoarthritis. The Vitamin D Council Blog & Newsletter, June 1, 2017.