Muscle Deficits Usually Persist Long after Total Knee Replacement

“Muscle deficits persist after unilateral knee replacement and have implications for rehabilitation. Physical Therapy. 2009 Oct;89(10):1072-9.”

From the study:

“Participants were 29 women and 19 men who were 55 to 75 years old and had undergone unilateral knee replacement surgery an average of 10 months earlier. The maximal torque and power of the knee extensor and flexor muscles were measured with an isokinetic dynamometer. The knee extensor muscle CSA was measured with computed tomography. The symmetry deficit between the knee that underwent replacement surgery (“operated knee”) and the knee that did not undergo replacement surgery (“nonoperated knee”) was calculated. Maximal walking speed and stair-ascending and stair-descending times were assessed.”

“The mean deficits in knee extensor and flexor muscle torque and power were between 13% and 27%, and the mean deficit in the extensor muscle CSA was 14%. A larger deficit in knee extension power predicted slower stair-ascending and stair-descending times. This relationship remained unchanged when the power of the nonoperated side and the potential confounding factors were taken into account.”

“Mizner et al reported that performance in stair-climbing and “stand-up-and-go” tests returned to the preoperative level at 2 months after surgery. Therefore, although functional ability may improve to the preoperative level, which already is severely impaired because of pain and long-term disuse, it rarely reaches the level in age-matched control subjects. For example, Walsh et al and Yoshida et al reported that people with knee replacement had a lower maximal walking speed and negotiated stairs more slowly than control subjects even beyond 1 year after surgery.”

“In particular, the ability to recover from a stumble is highly dependent on the power and coordination of the leg muscles. In addition, Portegijs et al found that, even in people who were healthy, a knee extension power deficit was associated with falls.”

Chad’s comments:

Results and conclusions of this study largely speak for themselves. I think the problem is several fold.

Expectations: Generally, after a TKA, patients are very pleased with the reduction in pain and their function quickly returns to better than they are used to. However, since they are used to considerable disability they stop treatment well before strength and power levels return to normal. Unfortunately, everyday living does not cause people to catch up to age-matched peers. As the patients continue to age, the weakness leads to lesser activity, accelerating them towards cardiovascular disease, osteoporosis, sarcopenia, frailty, etc.

Physical Therapy Techniques: Treatment techniques that include passive modalities:  light exercises such as heels slides, straight leg raises, bridging, rubber bands and mini-squats are not as up to the task with regards to strength gains as is progressive resistance exercise with real weights through a full range of motion. Properly applied electric muscle stimulation has been shown to be very helpful. In a number of recent studies, EMS is shown to prevent post-op muscle atrophy in the first place, leading to early and more complete recovery of both strength and muscle mass post-op. If however, treatment time is squandered on more faddish and less proven modalities, which right now seems to include foam rolls and ASTM, one might expect a less than optimal recovery when it comes to regaining lost muscle mass.

Insurance Policies: More than before, insurance companies like Medicare are cutting reimbursement, and worse, Medicare “replacement policies” are paying minimal flat rates while saddling patients with both high deductibles and copayments. This encourages therapists to cut treatment time per day to maximize profit, while at the same time makes patients unable to afford continued care. I know of one clinic in town that is scheduling patients with just 30 minutes of treatment per day, which I can’t imagine helps outcomes. Plus, if I were a patient I don’t think I would feel very inclined to pay a $40 or $50 copayment for that.

Like the problems, I think the solution is several fold. Alongside knee range of motion, use simple but objective functional tests like timed single leg balance, timed up and go, walking speed, stair climbing and 6 minute walk tests. These allow patients to make progress and compare themselves to where they should be with regards to function. Emphasize strength training early post-op which is better tolerated than most people (including me) would have thought. Utilize a number of single leg strength exercises performed concurrently with training of the non-surgical side. This lets both the patient and therapist gain a good understanding of where one leg is in relation to the other. Include hip and core strength and endurance exercise. Utilize aggressive stretch methods that emphasize total end range time and intensity, putting the patient in charge of both. This lessens both anxiety and muscle guarding because they know exactly what to expect and know they can stop at any time. Start aggressive electric muscle stimulation to both quadriceps and hamstrings immediately post-op and preferably at home pre-op. Lastly, progress the patient to gym type exercises and teach them to be independent with exercise programming. Encourage them to join their local fitness center and make full use of insurance covered fitness programs, encouraging senior fitness such as SilverSneakers. Home exercise programs are certainly better than nothing, but gym programs give the patients more options to work both muscle strength and cardiovascular endurance harder, through a fuller range of motion, with less impact.

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Thanks for reading my blog. If you have any questions or comments (even hostile ones) please don’t hesitate to ask/share. If you’re reading one of my older blogs, perhaps unrelated to neck or back pain, and it helps you, please remember Spinal Flow Yoga for you or someone you know in the future.


Chad Reilly is a Physical Therapist, obtaining his Master’s in Physical Therapy from Northern Arizona University. He graduated Summa Cum Laude with a B.S. Exercise Science also from NAU. He is a Certified Strength and Conditioning Specialist, and holds a USA Weightlifting Club Coach Certification as well as a NASM Personal Training Certificate. Chad completed his Yoga Teacher Training at Sampoorna Yoga in Goa, India.

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