African-Americans are more likely than Caucasians to have osteoarthritis, or OA, in the knee and in multiple large joints, but less likely than Caucasians to have it in their hands. And because of these differences, doctors might not notice when African-American patients have OA, according to a study analyzing how the joint disease presents in the two races.

“We think of multiple OA often being hand and knee or hands and hips and knee, which is more the pattern of Caucasian women. So we could miss [cases] in African-Americans who actually have large, weight-bearing joints that are involved,” explains study author Amanda E. Nelson, MD, an assistant professor of medicine in the Division of Rheumatology, Allergy, and Immunology at the University of North Carolina Thurston Arthritis Research Center in Chapel Hill.

This study in Arthritis & Rheumatism is part of the ongoing Johnston County Osteoarthritis Project, which studies OA and its risk factors in a rural, biracial population.

For this study, researchers analyzed thousands of X-rays of hands, knees, hips and spines of black and white participants older than age 45. They looked at 16 types of hand OA in more than 2,000 patients and 32 combinations of OA in multiple joints of 1,400 participants.

They found that African-Americans were two-and-a-half times as likely as Caucasians to have knee OA, and 77 percent more likely to have both knee and spine OA than Caucasians. Although it wasn’t determined to be statistically significant, African-Americans also had a 30 to 40 percent increased chance of having OA in a hip alone or in a hip, knee and back combined.

“All the large, weight-bearing joints were more likely to be involved together in African-Americans,” Dr. Nelson explains. “This is really the first study to look at this. We don’t really understand it yet.”

“I think it’s a very interesting article and it highlights the fact that, although osteoarthritis is so common, there is still a lot we have to learn about the clinical presentation of the disease, especially in different populations,” says Carla Scanzello, MD, PhD, of the department of rheumatology at Rush University Medical Center in Chicago. “Hand OA creates a different type of disability than OA affecting large joints like knees and hips. So understanding how those patterns differ in different individuals will allow us to apply treatment modalities and support in appropriate patient populations."

Dr. Scanzello also thinks doctors will pay attention to the high rate of spine OA in this research – because it was the most common type of OA in the entire study group, present in 62 percent of participants. She says that is important. That was followed by 42 percent with knee OA, 36 percent with hip OA and 32 percent with hand OA.

“We study knee and hip OA quite often and hand OA more often than just 10 years ago. But research studies focusing on spine OA are relatively few and far between,” Dr. Scanzello says.

Dr. Scanzello says she thinks this information will broaden the definitions used in research to categorize patients with osteoarthritis. “These [African-American] patients would have been excluded from strict studies of generalized OA using a definition based on hand involvement,” Dr. Scanzello explains. While there is no standard definition for generalized OA, the definition is often thought of as OA of the hands with nodal changes and involvement in some other joint, such as in the knee, back or feet. Dr. Nelson says many other definitions have been proposed but none is generally accepted.

While this is a research study and she says it isn’t directly translatable to practice, Dr. Nelson says she does hope over time the medical community will be on the lookout for OA in a variety of joints when diagnosing the condition in African-Americans.

“It would be nice if they looked at multiple joints – not just the joint that brought [the patient] in,” Dr. Nelson says. “They might have a different pattern and multiple, large-joint involvement, and there may be treatment interventions that could be directed at multiple joints if it were recognized.”

Although there is no treatment to cure or halt progression in OA, Dr. Nelson says education, weight loss, exercise and other similar measures can impact pain and quality of life. “Such measures might be recommended to someone more strongly if they were found to have OA in multiple, rather than a single, joint,” Dr. Nelson says.