Progressive strength training targeting the quadriceps — the large muscles on the front of the thigh — substantially improves strength and function following total knee replacement for treatment of osteoarthritis, according to a new study.

Osteoarthritis is the most common form of arthritis, causing pain, swelling and reduced motion of the joints. Its onset is frequently age-related and often affects the hands, knees, hips or spine.

Dr. Lynn Snyder-Mackler at the University of Delaware, Newark, and co-investigators randomly assigned a group of patients who had knee replacement surgery to 6 weeks of progressive strength training two to three times per week, with or without neuromuscular electrical stimulation. Patients who were eligible to participate in the study but opted out served as the "standard of care" control group.

Both rehabilitation groups significantly improved between baseline and 3 months, and between 3 and 12 months on all measures including active knee range of motion, quadriceps strength, as well as the Timed Up and Go Test, the Stair-Climbing Test, and the 6-Minute Walk Test.

Outcomes did not differ between the exercise-only group and the exercise plus electrical stimulation group.

Patients in the active rehabilitation groups also demonstrated substantially greater quadriceps strength and function 12 months after surgery than patients in the standard of care group.

According to the investigators, outcomes at one year "exceeded those previously reported in the literature, approaching the function of age-matched healthy older adults."