Studies show muscle weakness after total knee replacement (TKR) is common months and even years after the surgery. This study compares the force produced during a single-leg press after TKR. Nine patients with TKR were compared to nine adults without TKR (the control group).
This is the first study to measure force produced by the leg after TKR in a weight-bearing position. It's unique because force is examined across several joints using many muscle groups. This gives a better idea of what's going on in a fully weight-bearing position. Other studies have reported on forces in one joint at a time. Often only the knee extensor muscles are tested.
The authors report that there is much less force through the leg with the joint replacement. These measures were lower when compared to the patient's healthy leg and when compared to the control group. This shows that the entire leg, not just one set of muscles, has less power.
The researchers suggest that the loss of force in the leg with the TKR may be present even before the joint replacement. Pain from arthritis causes the patient to favor that leg. Gradual weakness occurs as a long-term effect of the arthritis.
Weakness before and after surgery will be the focus of the next study. The goal is to find out which exercises are needed before and after TKR to restore full force to the leg.
Mark D. Rossi, PhD, PT, CSCS, and Scott Hasson, EdD, PT. Lower-Limb Force Production in Individuals after Unilateral Total Knee Arthroplasty. In Archives of Physical Medicine and Rehabilitation. August 2004. Vol. 85. No. 8. Pp. 1279-1284.'