Kathy is a 68 year old female who has had chronic knee pain and achiness making it difficult to get around and do house chores. She has difficulty squatting to get dishes out of low cabinets or to pick up after her grandchildren. Her knees ache every morning when she gets out of bed and walks down her steps to the kitchen. She has been dealing with pain for the last 3 years, but she noticed that it had gotten worse. She now reluctantly decides to have a total knee replacement. What exactly does this mean?
Patients often come to physical therapy prior to a joint replacement. Often they are sent to physical therapy to maintain flexibility and strength to delay having surgery. When symptoms become too uncomfortable making basic mobility difficult, patients will consult with their orthopedic surgeon to elect to have the total joint replacement.
During this procedure the joint surfaces are replaced to allow smooth articulation and greater range of motion. The rehabilitation or physical therapy will start after this procedure. There are many websites with animations of the process.
(Examples: https://www.webmd.com/osteoarthritis/knee-replacement-18/video-knee-replacement-inside-look; https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/minimally-invasive-total-knee-replacement
THE IMPORTANCE OF KNEE EXTENSION AFTER TOTAL KNEE REPLACEMENT.
A total knee replacement is a major procedure. Individuals who typically have a total knee replacement have had long standing knee pain most commonly from osteoarthritis. These patients have difficulties with functional activities related to deep knee bending, standing and walking. These symptoms may have been ongoing for many years.
Once the total knee replacement is performed many patients do not realize that the rehabilitation process is just as important.
During rehabilitation one of the first landmark goals is achieving full knee extension, with a goal of knee extension that is symmetric to the opposite side. Most patients do not realize how important knee extension is. After many months of having limited and painful knee flexion (or bending of the knee) they often are most concerned about how much their knee can bend. Knee extension is important for symmetric standing. It allows you to stand evenly on both legs. If your operated knee remains in a flexed position of 10 degrees, it will indirectly make the operated leg an inch or so shorter. Having a leg length differential can then lead to an asymmetric limp when you walk. This makes walking awkward and does not allow for even weight distribution between both of your legs.
Knee extension will be measured with a goniometer. Your therapist will align one end of the goniometer with your hip using a bony landmark called your greater trochanter. The other end will be aligned with the outside ankle bone or the lateral malleoli. The axis of the goniometer will be centered over your knee joint. This allows your therapist to determine your angle of knee extension.
Immediately after having your total knee replacement, while in the hospital, patients will be placed in positions to promote knee extension. Usually pain is well managed in the hospital so patients do not mind this. When patients are discharged home and pain medications may be different, stretching into knee extension is not always as comfortable. Some patients find it more comfortable to have a small pillow under the operated knee. This is not a good idea for prolong periods of time as this places the knee in a flexed position. Patient is then at risk of knee flexion contracture.
When your therapist encourages you to work for full knee extension hopefully you will understand the importance of this process.