Optimal Range of Motion After Total Knee Replacement
Pain, loss of motion, and limited function are the main reasons older adults choose to have a total knee replacement (TKR). And though many obtain pain relief, range of motion and function are not always fully restored.
But what is the optimal range of motion needed in the knee for everyday activities such as walking and climbing stairs? This study from the Center for Hip and Knee Surgery at St. Francis Hospital in Indiana takes a look at this question. They went back and reviewed over 5,500 patient charts who had a TKR.
A comparison was made between motion, pain, walking and stair-climbing ability, and knee function before and after TKR. Everyone had a posterior cruciate-retaining implant. This type of knee replacement leaves the posterior cruciate ligament (PCL) intact. The PCL helps hold the knee stable and prevents too much backward motion of the tibia under the femur (thighbone).
Previous studies have shown that 90-degrees of motion is needed to go up and down stairs. Getting up from a chair requires just slightly more motion (93 degrees). And lifting an object requires at least 117-degrees of flexion.
These movements and activities are all that are needed by most adults in a Western culture after TKR. Adults in other cultures requiring more squatting, kneeling, and sitting cross-legged need between 111 and 165 degrees of knee flexion to use these positions.
The results of this study showed that patients with posterior cruciate-retaining TKRs had the least pain and best results when their knee flexion motion was 128 to 132 degrees. There wasn't much difference in function for patients with range of motion just above or below these figures. But stair climbing was improved with motion between 133 and 150 degrees.
The authors concluded that at some point, there may be a limit to the benefits gained by a higher range of motion after TKR. Patients who get between 128 and 132 degrees of knee flexion seem to have good function for everyday activities. Anyone who engages in activities requiring kneeling, squatting, or sitting cross-legged may need additional rehab to obtain enough motion to accomplish these tasks.
Merrill A. Ritter, MD, et al. The Effect of Postoperative Range of Motion on Functional Activities After Posterior Cruciate-Retaining Total Knee Arthroplasty. In The Journal of Bone and Joint Surgery. April 2008. Vol. 90-A. No. 4. Pp. 777-784.