A stronger quadricep, the muscle responsible for straightening the leg at the knee joint, does not lead to damage in the knee and helps prevent the deterioration of cartilage behind the knee cap among those with knee osteoarthritis, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Washington, DC.
Strengthening exercises for the quadriceps muscle of the leg generally have been viewed as beneficial to the knee joint in those with knee osteoarthritis. However, there has been some concern that greater quadriceps strength may actually be harmful to the tibiofemoral joint, the main joint in the knee, especially if the knee is malaligned because altered biomechanics may put more stress on the joint. Also, little information has been available on how quadriceps strength may affect the patellofemoral joint of the knee (the smaller joint between the knee cap and femur), which is a frequent site of osteoarthritis at the knee.
To examine this further, researchers followed 265 men and women, average age 67, with symptomatic knee osteoarthritis for 30 months. Each participant's quadriceps strength was measured at the outset of the study, and MRIs of the knee were taken at the beginning of the study as well as at 15 and 30 months of follow-up. Cartilage loss based on knee MRIs at both the tibiofemoral and patellofemoral joints was then determined during follow-up.
Study results indicated that, in fact, greater quadriceps strength leads to no worsening of cartilage loss at the tibiofemoral joint even in those with malaligned knees. Further, this increased strength, which tends to better maintain knee cap (patella) stability towards the inner side of the knee, does protect against cartilage loss at the outer (lateral) part of the patellofemoral joint.
"Those with better quadriceps strength were less likely to lose cartilage behind the knee cap," explains Shreyasee Amin, MD, Assistant Professor of Medicine, Mayo Clinic, Rochester, Minnesota, and principal investigator of the study. "This makes sense as a stronger quadriceps would be better able to keep the knee cap from moving laterally and tracking abnormally with joint movement. This study should encourage patients with knee osteoarthritis to speak with their doctors about how best to improve quadriceps strength."