The reliability of the American Knee Society Score

We have investigated the reliability of the American Knee Society Score (AK S), a widely used functional outcome score for knee arthroplasty, 29 subjec ts mere assessed in random order by 6 observers, each patient seen twice by each observer. The interobserver reference intervals were 16 points for th e Knee Score (0-100 points) and 21 points for the Function Score (0-100 poi nts), The intraobserver reference intervals were smaller, 11 points and 13 points for the Knee Score and the Function Score, respectively. The presenc e of arthritis in other joints and general debility did not affect the reli ability of the scores. The more experienced observers had greater intraobse rver reproducibility. Notably, we found moderate agreement between observer s in the subjective variables, while the objective variables produced lower levels of agreement. The high inter- and intraobserver variations of the AKS makes estimation of score change questionable. Reliable use of the AKS would necessitate repea ted evaluation by an experienced observer.