Researchers tracking knee pain in the population of a North Carolina county say the knee osteoarthritis risk is far higher than experts had known. The results of their latest study suggest that nearly 1 in 2 people will develop osteoarthritis in a knee before they reach the age of 85, with the risk approaching 2 in 3 for people who are overweight or obese.

By comparison, 1 in 8 women will get breast cancer in her lifetime and 1 in 3 men and 2 in 5 women will get diabetes in their lifetimes – making osteoarthritis of the knee more common than either of those ailments.

“This indicates a higher risk of arthritis than has been appreciated before,” said John Hardin, M.D., a rheumatologist and Chief Scientific Officer of the Arthritis Foundation, a national volunteer health organization based in Atlanta. The study was published in the Sept. 15, 2008, issue of Arthritis Care & Research.

“This is a very important knee osteoarthritis study. It is very well done, and I think it’s going to be one of the cornerstones of our discussions of arthritis in the future,” Dr. Hardin said. 

For this analysis, a team of investigators from the Centers for Disease Control and Prevention in Atlanta and the University of North Carolina at Chapel Hill followed more than 3,000 people living in six townships of Johnston County, NC, for almost two decades. 

The knee osteoarthritis study participants were asked to answer a battery of interview questions and given a slew of medical tests, including X-rays of their hips, knees, spine and hands. Five to seven years later, they were asked to repeat the process. 

After examining the baseline and follow-up data, researchers estimated that the risk of having symptoms of osteoarthritis in at least one knee by age 85 was 45.5 percent. Race, sex and education level seemed to have no effect on the risk of getting arthritis in a knee. 

But risk escalated significantly with increasing body weight. Those who maintained a normal weight over the course of their lives had the lowest lifetime risk of any group in the study – 30 percent. Those who were normal weight at age 18, but overweight or obese at the start of the study (27 or more years prior) and at their follow-up exams, had the highest lifetime risk of knee osteoarthritis – 60 percent.