In the United States, 200,000 knees are replaced with artificial joints each year. This operation is called total knee replacement, or TKR. Most often, one knee is replaced at a time. For people with severe arthritis in both knees, it is possible to have both joints replaced at the same time. This is called bilateral TKR.
Until now, researchers have studied single knee replacements. Information about motion, strength, and function has been collected. The data have been compared for different methods of surgery, types of knee joints, and methods of rehabilitation.
The first study of knee strength after bilateral TKR has been reported. Physical therapists measured strength in both legs before bilateral TKR. Strength was measured again 30 and 60 days after TKR. (This is the earliest that strength has been measured after single or bilateral TKR.) After surgery, all patients took part in a physical therapy program three times a week for eight weeks.
Strength dropped quite a bit in the first 30 days after surgery. However, both legs were equal in strength and motion. The greatest improvement in strength happened 30 to 60 days after surgery. Since both knees were treated at the same time, there was no “good” or “bad” knee, and patients couldn’t favor the “good” knee during recovery. Patients used both knees equally.
The first month after TKR is the most important time to build muscle strength. At 30 days, the legs are much weaker than before surgery. With continued exercise, strength improves in the second month. Future studies will look at balance and function during the first 60 days after TKR. This will help physical therapists improve on existing exercise programs.