The Knee Society rating system was first promulgated during the late 1980's and has become the standard clinical evaluation system for reporting results for patients undergoing Total Knee Replacement. Most major journals strongly encourage that total knee manuscripts include Knee Society rating scores as part of the result section.
The Knee Society System was a logical outgrowth of the Hospital for Special Surgery (HSS) Rating system of the 1970's. The HSS system, although widely used, combined an evaluation of both the operated knee and the patient's general function in one score. This at times was problematic. If a patient had no pain and excellent range of motion, however could not walk because of arthritis in the other leg, or from a chronic medical problem, the total score was artificially low.
The Knee Society System separates findings in the operated knee with findings in the patient's function. As such the Knee Score is not artificially affected by comorbid conditions. The Knee Score consists of points given for pain, range of motion, and stability in both the coronal and sagittal planes, with deductions for fixed deformity, and extensor lag. The Function Score consists of points given for the ability to walk on level surfaces, and the ability to ascend and descend stairs, with deductions for the use of external supporting devices.
The Knee Society Score is usually reported as the two scores, Knee Score and Function Score, rather than a summation score. There is, as well, a Knee Society Radiographic Evaluation system, however discrete points are not given for individual parameters on X Rays.
Richard S. Laskin, MD