The big event is over. Now what? Your brand new knee is not like a car part that is 100 percent ready to go after installation. Your new knee needs some aftercare and some rehabilitation in order for you to be completely satisfied with it.
Total satisfaction is based on two primary goals: no pain and adequate range of motion. Barring any complications like infections or nerve damage, the rehabilitation process should go smoothly enough for you to be able to achieve both goals. What is adequate range of motion? Your knee needs to be able to do certain things during daily activities, like getting you up out of a chair or climbing stairs. Researchers have determined that in order for a new knee to perform activities of daily living, it needs at least 110o degrees of flexion. Researchers also have determined that you only have 12 months from the time of surgery to gain those degrees of motion. (1)
That’s easier said than done; so, the rehabilitation process needs to begin in earnest right after surgery. On the first day, your new knee will be strapped into a device that provides for continuous passive range of motion. You don’t want stiffness to lock up the new implant. A continuous passive motion machine cycles the new knee through motion to help prevent a frozen knee. Next, a physical therapist will teach you an exercise program that includes straight leg raises, active knee flexion and lunges. This exercise program will serve you well over the coming months as you try to gain as much function in the new knee as possible in the first 12 months.
After the first 12 months, you will not be able to improve your knee function much more than you have already. That is why early rehabilitation is so important after total knee replacement surgery. If you are expecting more than 110 degrees of flexion after a total knee arthroplasty, you might be disappointed depending on the type of artificial knee you have in place. One group of researchers compared a variety of knee implants by using a computer-generated simulation. They found that "as a group, the posterior stabilized designs achieved higher flexion than the cruciate retaining designs, primarily due to the engagement of the femoral cam and tibial post during high flexion." Accordingly, the cruciate retaining designs are not able to achieve much more than 105degrees. Keep this in mind if you are planning to have knee implant installed and desire maximum range of motion.
So, congratulations, you have a new knee Now, get to work because the rehabilitation process is just beginning.
(1) Arch Phys Med Rehabil. 2014 Jun;95(6):1135-40
Specialist in Pain Management and Spine Rehabilitation