I had a total knee replacement six weeks ago and just had my six-week checkup. After six week's worth of intensive exercises my muscle strength just hasn't come back like I thought it would. What's going on?

Doctors and therapists have long thought that patients are weak in the early days and weeks after total knee replacement (TKR) because of pain. Efforts are made to reduce pain quickly. The idea is gaining control of pain will help restore motion and improve function. But according to a new study, pain control may not be enough to prevent loss of muscle strength.

Muscle atrophy and lack of activation may be the real culprits. Surgical trauma causes muscle inhibition. The leg muscles are unable to contract. This is called failure of voluntary muscle activation.

A recent study of 20 patients before and after TKR showed a big loss of force-producing ability by the quadriceps muscle. Measurements of muscle contraction were taken 10 days before and one month after the operation.

They found quadriceps strength was down by 62 percent despite an active rehab program. Improving strength may require a different kind of exercise program--one that gets each muscle fiber to contract.

No doubt your exercise program has helped you. It may be time to look into a different kind of exercise now. Talk to your doctor and your therapist about the use of biofeedback or electrical stimulation to activate muscle recruitment.