is a self report questionnaire with 42-items in 5
separately analyzed subscales of pain, other symptoms,
function in daily living, function in sport and recreation,
and knee–related quality of life [31]. The tool has good
test-retest reliability with ICC (2,1) values in 26 patients
6 months post TKA of 0.73 (QOL), 0.74 (Sport/recreation),
0.82 (ADL), 0.85 (Symptoms), and 0.94 (Pain). Good
content validity demonstrated by 90 % of patients who
regarded improvement in the subscales Pain, Symptoms,
Activities of Daily Living, and knee-related Quality of Life
to be extremely or very important when deciding to have
their knee operated on. The KOOS is responsive on all
subscales particularly the knee-related Quality of Life subscale
(effect size 2.86 at 6 months post TKA and 3.54 at
12 months post TKA)