Research data shows patients get relief from pain after a total knee replacement (TKR). But residual disability is common as you've noticed. Most patients get enough motion and strength back to do their daily tasks.
Recovery to pre-TKR levels just doesn't happen for the average person. A year after the operation, most patients go up and down stairs at half the speed of healthy adults the same age. Squatting, gardening, and heavy housework often go by the wayside. Patients with TKRs walk slower and shorter distances than before the surgery.
Physical therapists are studying this problem. They hope to find ways to prevent or overcome these problems. A recent study from the University of Delaware suggests strengthening the quadriceps (thigh) muscle may be a key factor.