Doctors know that people with osteoarthritis in their knees tend to have weak muscles around the affected joint, and exercising to strengthen those muscles has been shown to reduce pain and improve mobility. But they've generally assumed that the muscle weakness develops because pain prevents the arthritis sufferer from fully using the joint.
Now a study of elderly people suggests that, at least for women, the muscle weakness may come first--or may at least develop very early in the disease. The weakness may then contribute to the progressive joint damage.
Osteoarthritis, a major cause of disability in older people, is degeneration that often occurs in joints that are overused or bear a lot of weight, particularly knees and hips.
Researchers at Indiana University School of Medicine studied 462 people over 65 to examine the relationship between muscle weakness and knee arthritis. Participants underwent X-rays of the knees and answered questions about pain and function. Muscle strength was also tested.