Development of a new Knee Society scoring system

Abstract

Background: The Knee Society Clinical Rating System was developed in 1989 and has been widely adopted. However, with the increased demand for TKA, there is a need for a new, validated scoring system to better characterize the expectations, satisfaction, and physical activities of the younger, more diverse population of TKA patients.

Questions/purposes: We developed and validated a new Knee Society Scoring System.

Methods: We developed the new knee scoring system in two stages. Initially, a comprehensive survey of activities was developed and administered to 101 unilateral TKA patients (53 women, 48 men). A prototype knee scoring instrument was developed from the responses to the survey and administered to 497 patients (204 men, 293 women; 243 postoperatively, 254 preoperatively) at 15 medical institutions within the United States and Canada. Objective and subjective data were analyzed using standard statistical and psychometric procedures and compared to the Knee Injury and Osteoarthritis Score and SF-12 scores for validation. Based on this analysis, minor modifications led to the new Knee Society Scoring System.

Results: We found the new Knee Society Scoring System to be broadly applicable and to accurately characterize patient outcomes after TKA. Statistical analysis confirmed the internal consistency, construct and convergent validity, and reliability of the separate subscale measures.

Conclusions: The new Knee Society Scoring System is a validated instrument based on surgeon- and patient-generated data, adapted to the diverse lifestyles and activities of contemporary patients with TKA. This assessment tool allows surgeons to appreciate differences in the priorities of individual patients and the interplay among function, expectation, symptoms, and satisfaction after TKA.

Figures

Fig. 1

A graph show the most important activities involving the knee, as reported by the patients with TKA enrolled in this study.

Fig. 2

A graph shows the distribution of values of the Objective Knee Score for patients in the preoperative and postoperative study groups. Preop = preoperative; postop = postoperative.

Fig. 3

A graph shows the average values of the Objective Knee Score (maximum: 100 points), Satisfaction Score (maximum: 100 points), and Expectation Score (maximum: 15 points), recorded using the prototype Knee Society instrument, for both male and female patients in the preoperative and postoperative groups. Error bars = SD. Preop = preoperative; postop = postoperative.

Fig. 4

A graph shows the average values of the Function Score (maximum: 110 points) and its subscales, recorded using the prototype Knee Society instrument, for both male and female patients in the preoperative and postoperative groups. Error bars = SD. Preop = preoperative; postop = postoperative.

Fig. 5

A graph shows the distribution of levels of patient satisfaction, as recorded by the prototype Knee Society instrument, for the preoperative and postoperative patient groups. Preop = preoperative; postop = postoperative.

Fig. 6

A scatterplot shows the values of the Satisfaction Score and the Function Score, as recorded by the prototype Knee Society instrument. Low Knee Society Function Scores are typically associated with low levels of patient satisfaction with the outcome of TKA.