Stronger Leg Muscles Can Protect Against Knee Osteoarthritis

Knee osteoarthritis (OA) occurs when the cartilage that cushions the ends of the bones in the knee joint deteriorates over time. As this cushion wears down, the joint doesn't function as well and may be painful.

Mayo researchers, in collaboration with researchers from Boston University and the University of California, San Francisco, studied 265 men and women diagnosed with knee OA. They performed magnetic resonance images (MRIs) of participants' knee joints at the beginning of the study and again at 15 months and 30 months. Based on these MRIs, researchers determined how much cartilage loss occurred over time at the two joints of the knee: the tibiofemoral joint, where the thigh bone (femur) meets the lower leg bone (tibia); and the patellofemoral joint, behind the kneecap (patella).

When the study began, researchers also had measured the strength of participants' quadriceps muscles (leg muscles in the upper thigh). Analyzing these measurements, researchers observed that participants who had greater quadriceps strength had less cartilage loss within the lateral compartment of the patellofemoral joint, which is frequently affected by OA.

"A stronger quadriceps muscle helps keep the patella from moving laterally and tracking abnormally with movement," says Shreyasee Amin, M.D., Mayo rheumatologist and the study's lead researcher. "Our study results emphasize that it's important to encourage people with knee osteoarthritis to maintain strong quadriceps muscles as recommended by their physician."

The exact cause of OA isn't known. Researchers suspect a combination of factors, including being overweight, the aging process, joint injury or stress, heredity and muscle weakness. Pain is the major complication of OA. The degree of pain can vary greatly, from mild inconvenience to a debilitating condition that interferes with daily activities.

Other members of this Mayo-led research team included: Kristin Baker, Ph.D., Jingbo Niu, M.D.; D.Sc., Joyce Goggins; David Hunter, M.B.B.S., Ph.D.; and David Felson, M.D., all from Boston University; and Ali Guermazi, M.D.; Mikayel Grigoryan, M.D.; both from the University of California, San Francisco. This work was supported by grants from the Arthritis Foundation, the National Institutes of Health and the Bayer Corporation.