Knee osteoarthritis (OA) runs in the family, according to findings reported in the Annals of Rheumatic Diseases (September 2004). The results suggested that an individual's genes play a role in the condition. The study involved 490 individuals with severe knee OA, 773 of their siblings over the age of 40, and 1729 other individuals with knee pain. Using x-rays of the knees of the siblings and the participants with knee pain, the researchers were able to look for signs of OA.

The researchers found that the siblings were >2 times as likely to have knee OA, compared with the other participants. The results remained the same even when the researchers took into account major risk factors such as smoking, age, gender, and being overweight. As for the genetic link, the risk for siblings was spread across different ages, but brothers were more likely to have OA than sisters.