de Laat FA, Rommers GM, Geertzen JH, Roorda LD. Construct validity and test-retest reliability of the Questionnaire Rising and Sitting Down in lower-limb amputees. Objective To investigate the construct validity and test-retest reliability of the Questionnaire Rising and Sitting Down (QR&S), a patient-reported measure of activity limitations in rising and sitting down, in lower-limb amputees. Design Cross-sectional study. Setting Outpatient department of a rehabilitation center. Participants Lower-limb amputees (N=171; mean age ± SD, 65±12y; 71% men; 83% vascular cause) participated in the study, 33 of whom also participated in the reliability study. Interventions Not applicable. Main Outcome Measures Construct validity was investigated by testing 8 hypotheses: limitations in rising and sitting down according to the QR&S would be: (1) greater in lower-limb amputees who are older, (2) independent of level of amputation, (3) greater in lower-limb amputees with a bilateral amputation, and (4) greater in lower-limb amputees who had rehabilitation treatment in a nursing home. Furthermore, limitations in rising and sitting down will be positively related to activity limitations according to (5) the Locomotor Capabilities Index (LCI), (6) the questions about rising and sitting down in the LCI, (7) the Climbing Stairs Questionnaire, and (8) the Walking Questionnaire. Construct validity was quantified with an independent t test and Pearson correlation coefficient. Test-retest reliability was assessed with a 3-week interval and quantified with the intraclass correlation coefficient (ICC), standard error of measurement, and smallest detectable difference (SDD). Results Construct validity (7 of 8 null hypotheses not rejected) and test-retest reliability were good (ICC=.84; 95% confidence interval, .65–.93; standard error of the measurement=6.7%; SDD=18.6%). Conclusions The QR&S has good construct validity and good test-retest reliability in lower-limb amputees.