“We hear a lot about why the obesity epidemic is so important,” said Joanne Jordan, MD, PhD, professor of medicine and orthopedics at the University of North Carolina at Chapel Hill. “We hear that you need to lose weight to prevent diabetes or lose weight to prevent heart disease. We never hear that you need to lose weight to prevent arthritis. But it is critical to realize that if you gain weight, you’re going to get arthritis in your knees and you’re going to be miserable.”

Previous studies have shown that being just 10 pounds overweight increases the force on the knee by 30 to 60 pounds. In another study of osteoarthritis in a population in Framingham, Mass., researchers estimated that a woman who lost 11 pounds or about 2 Body Mass Index (BMI) points, decreased her risk of osteoarthritis by more than 50 percent.

Injuries also elevated knee osteoarthritis risk; 58 percent of those with a history of knee damage could expect to develop arthritis later in life.

“The key to preventing disease is preventing the injury to begin with,” Dr. Hardin said.  “Once the damage is done and the cartilage has been injured, it’s very hard to think about how you might recover from that,” he added.

Dr. Hardin said keys to preventing osteoarthritis include maintaining proper weight and preventing injury. And doing one helps with the other. Keeping muscles strong, particularly the quadriceps, the big muscles on the front of the thighs, helps prevent knee injuries.

Arthritis is a major cause of disability in the United States. There are more than 100 types of arthritis and related conditions, and the most common kind is osteoarthritis.

Data collected by the Healthcare Cost and Utilization Project, a government survey, show osteoarthritis accounted for $10.5 billion in hospital charges in 2006, making it a more expensive condition than pneumonia, stroke, or complications from diabetes. In fact hospital admission for arthritis more than doubled from 1993 to 2006.

Knees, hips and fingers are the joints where osteoarthritis is most commonly diagnosed. Early symptoms of knee osteoarthritis include pain, stiffness in the joint in the morning that lasts more than 30 minutes, instability or buckling, a grinding or cracking noise in the joint, and swelling or inflammation.

“People should seek the help of their physicians when symptoms first appear,” Dr. Hardin said. “It’s not something to write off because there are things that can be done.”