STUDY DESIGN: A cross-sectional study with a test-retest design. OBJECTIVES: To assess measurement properties of the physical fitness questionnaire, the 6-minute walk test, the stair test, the hand-grip test, the 30-second sit-to-stand test, and the fingertip-to-floor test in patients with various musculoskeletal conditions (MSCs). BACKGROUND: Patients suffering from MSCs tend to be more deconditioned and less physically active than healthy people. Physiotherapists should, therefore, focus on health-related physical fitness in addition to their patients' specific MSCs to offer optimal treatment. To enable good decision making, a core set of feasible measures with acceptable measurement properties is needed. METHODS: Eighty-one patients with MSCs (57.6 ± 14.2 years of age) were recruited from outpatient physiotherapy clinics. Relative reliability was analyzed with intraclass correlation coefficient model 2,1, and absolute reliability with standard error of measurement and smallest detectable change. Construct validity was assessed with a priori hypotheses. Time spent and assistance needed to accomplish the measures were used to assess feasibility. RESULTS: The 6-minute walk test, the hand-grip test, and the physical fitness questionnaire showed acceptable reliability (49 m, 4 kg, and 2 points, respectively) and construct validity. The stair test showed acceptable reliability (8 seconds) but not validity. The 30-second sit-to-stand test showed acceptable validity but not reliability (4 sit-to-stands), whereas the fingertip-to-floor test showed neither acceptable reliability (9 cm) nor validity. CONCLUSION: The 6-minute walk test, the hand-grip test, and the physical fitness questionnaire can be recommended as a core set of reliable and valid measures to assess health-related physical fitness in patients with various MSCs.