BACKGROUND: Knee-specific quality-of-life instruments are commonly used outcome measures. However, they have not been compared for their ability to detect symptoms and disabilities important to patients. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 1. METHODS: Subjective portions of 11 knee-specific instruments were consolidated. The frequency and importance of each item were assessed. One hundred fifty-three patients with anterior cruciate ligament ruptures, isolated meniscal tears, or osteoarthritis were polled. Instruments were ranked according to the number of items with high mean importance, high frequency importance product, and low mean importance, and according to the number endorsed by at least 51% of patients. RESULTS: For anterior cruciate ligament tears, the Mohtadi quality-of-life instrument scored highest in 3 categories. For meniscal tears, the Western Ontario Meniscal Evaluation Tool scored highly in all 4 categories. For osteoarthritis, the Western Ontario and McMaster Universities Osteoarthritis Index scored highly in 4 categories. Of the general knee instruments, the International Knee Documentation Committee Standard Evaluation Form and the Knee Injury and Osteoarthritis Outcome Score scored favorably. CONCLUSION: The Mohtadi quality-of-life instrument, Western Ontario Meniscal Evaluation Tool, and Western Ontario and McMaster Universities Osteoarthritis Index-disease-specific instruments-contain many items important to patients. Of general knee instruments studied, the International Knee Documentation Committee Standard Evaluation Form and the Knee Injury and Osteoarthritis Outcome Score contain the most items important to patients. CLINICAL RELEVANCE: This study guides clinicians and researchers in selecting instruments that ensure that the patient's perspective is considered for outcome studies involving 3 common knee disorders.