Even though one in five people develops osteoarthritis (OA), little is known about what causes the disease. However, because the condition is so common, researchers have always suspected a genetic link. Family and twin studies show that osteoarthritis can be inherited. But researchers scanning genomes (every gene in the body) looking for changes that may increase risk of OA don’t have a straightforward path.

“Osteoarthritis is probably a multi-gene disease and there’s likely an interaction between the environment and genetic susceptibility,” says Joanne Jordan, MD, an arthritis researcher and chief of Rheumatology, Allergy, and Immunology at the University of North Carolina in Chapel Hill.

Studying many aspects of genetics may help researchers identify people who are at higher risk of developing OA, such as those whose risk factors include family history of OA, hormonal changes, injury or obesity.

Although such complexity makes studying the genetics of OA very difficult, over the past decade or so, OA researchers have taken advantage of an abundance of improving technologies to pinpoint small genetic variations (called alleles) that may increase the risk of osteoarthritis. One technique allows researchers to study the genome of large populations of research participants. In another effort, scientists examining the disease on a molecular level use sensitive new assays to detect changes in chromosomes that may herald early changes that eventually progress to OA’s hallmark cartilage damage.

Two recent studies show the power of these technologies to spot people who may harbor the genetic underpinnings of OA. The goal of these studies is to detect OA at an early stage and then to find new treatments before the joints reach end-stage disease for which the only treatment is total joint replacement.

Just as our bodies don’t work as well as we age, cells get sluggish with aging, too. Like other aging cells, the cells that produce and maintain cartilage, called chondrocytes, go into a kind of sleep, or senescence. Once chondrocytes reach this slumber, they can’t perform the tasks necessary to keep cartilage healthy, such as responding to growth factors and switching certain genes on or off. Without the right genes working in unison, cartilage breaks down and can’t be repaired, says Jean-Marie Delaissé, PhD, Head of Research in the Clinical Research Unit at Vejle Hospital in Denmark.