The Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS), originally developed in English, is a valid and reliable self-reported instrument used for patients with various painful knee conditions. We adapted the KOS-ADLS to Turkish and tested its reliability and validity. We enrolled 142 patients with knee pain in the study. The patients were randomized into two groups: Group 1 (n = 75) completed the questionnaire twice a week for assessing test-retest reliability and Group 2 (n = 67) answered the questionnaire and performed additional tests for assessing validity. The intraclass correlation coefficient ranged from 0.98 to 0.99 with high internal consistency (Cronbach's alpha, 0.89). Validity-related tests included pain measurement with a visual analog scale and functional tests, including time measurements for the get-up-and-go and ascending/descending stairs tests. The visual analog scale score correlated with total score (r = 0.56), function total score (r = 0.53), and symptom total score (r = 0.45). The ascending/descending stairs test correlated with total score (r = 0.47), function total score (r = 0.49), and symptom total score (r = 0.31). The get-up-and-go test weakly correlated with all three scores. The Turkish version of the KOS-ADLS is reliable and valid in evaluating the functional limitations of patients with knee pain.