THE INFLUENCE OF AGE, GENDER AND BODY MASS INDEX ON KNEE SOCIETY SCORES BEFORE AND AFTER TOTAL KNEE REPLACEMENT

Abstract

Pre- and post-operative Knee Society Scores for 2105 Total Knee Replacements (TKRs) with minimum three year follow-up were evaluated. The effect of gender, age at operation and BMI at operation on Knee Society Data at pre-operative review, at one year post-operatively and at three years after TKR was analysed.

Total Knee Score pre-operatively, and at both one year and three year review was found to be independent of gender, age and BMI. There was no effect of the three demographic variables on the component scores for pain, range of motion, stability, alignment, extensor lag and flexion contracture.

Lower Function Scores were associated with female gender (p< 0.001), age greater than 70 at time of operation (p≤0.004) and obesity (p< 0.001). Median Function Scores were consistently higher in males than females by 5 points pre- and post-operatively (p< 0.001). At three years post-operatively, the median Function Score in the 80 and over age group was lower than all other age groups (p< 0.001), by between 15 and 20 points. Whilst the normal and overweight groups had similar Function Scores the class I obese and class II obese groups consistently had lower median Function Scores by 5 (p< 0.001) and 10 points (p< 0.001) respectively.

We conclude that whilst the Knee Score and its component scores are independent of gender, age and BMI, all three of these demographic variables can be associated with significant differences in Function Score.