Two new studies shed light on some of the differences in osteoarthritis (OA) between African-Americans and whites. They add to an ongoing effort by researchers to explore factors, including race, that may influence how the disease progresses and how to develop more targeted therapies.

The first study, published recently online in Arthritis Care & Research, found blacks are about half as likely to get hip OA as whites. But once they have it, blacks have an equal risk for progression of the disease as whites.

This study also found that blacks are equally likely to develop knee OA as whites, but more than 50 percent more likely to have it progress. The findings are based on analysis of data from the Johnston County Osteoarthritis Project, a long-term study of more than 3,000 black and white residents in rural North Carolina.

“Knowing people are at a higher risk for progression means you need to get early intervention for those folks so [the arthritis] doesn’t progress more,” explains senior study author Joanne M. Jordan, MD, director of the Thurston Arthritis Research Center at the University of North Carolina at Chapel Hill. “They might be targeted for interventions such as weight loss, increased physical activity, enrollment in self-management courses, corrections of malalignment and assessment for assistive devices.”

Dr. Jordan says there are many questions relating to racial differences still to be studied, beginning with the reason for these variances. She says possibilities include weight, anatomical differences (for example, the shape of the joint) and/or occupational, genetic or dietary factors.

The second study, also published online recently in Arthritis Care & Research, surveyed almost 800 people, age 50 or older, with moderate to severe knee OA. Within the survey were questions about a participant’s race, social support network and whether he or she would consider having total knee replacement (TKR) surgery.

Researchers found that blacks were significantly less willing than whites to undergo TKR, which the study authors characterize as an “effective and cost effective intervention” for advanced knee OA. And although blacks reported having less social support than whites – defined, for example, as being less likely to be married – the study found that the lack of social support wasn’t a barrier to them getting TKR surgery. Previous studies have suggested that blacks may instead avoid getting the procedure due to other factors, such as worries about the efficacy and risks of the procedure, and lack of complete trust in their physician’s recommendations.