Using examples from the field of anterior cruciate ligament rehabilitation, this review provides sports and health practitioners with a comprehensive, user-friendly, guide to selecting outcome measures for use with active populations. A series of questions are presented for consideration when selecting a measure: is the measure appropriate for the intended use? (appropriateness); is the measure acceptable to patients? (acceptability); is it feasible to use the measure? (feasibility); does the measure provide meaningful results? (interpretability); does the measure provide reproducible values? (reliability); does the measure assess what it is supposed to assess? (validity); can the measure detect change? (responsiveness); do substantial proportions of patients achieve the worst or best scores? (floor and ceiling effects); is the measure structured and scored correctly? (dimensionality and internal consistency); has the measure been tested with the types of patients with whom it will be used? (sample characteristics). Evaluation of the measure using these questions will assist practitioners in making their judgements.