Anterior cruciate ligament (ACL) injuries, meniscus tears and osteoarthritis (OA) are common conditions affecting the knee that lead to substantial pain and limitations in physical function. Assessment of the patient's perception of pain and physical function are important to measure the impact of these conditions affecting the knee as well as the effectiveness and efficacy of interventions aimed at ameliorating these conditions. Assessment of patient-reported pain and physical function has traditionally made use of a variety of patient-reported outcome (PRO) measures that were developed using methods consistent with classical test theory, resulting in a fixed set of items administered to all individuals regardless of the appropriateness of the items for a specific individual. Advances in test theory, namely item response theory (IRT), have made computer adaptive testing (CAT) a reality. In CAT, items tailored to the individual are administered to more efficiently and precisel determine the status of an individual. The Patient-Reported Outcome Measurement Information System (PROMIS), which is an NIH Roadmap Initiative, has created calibrated item banks to permit CAT for multiple dimensions of health, including pain interference and physical function. Further research is needed to provide validity evidence for interpretation and use of the pain interference and physical function CATs for patients with a variety of common knee conditions including ACL injuries, meniscus tears or OA. The overall purpose of this application is to provide evidence to support the interpretation and use of the PROMIS pain interference and physical function item banks and CATs within the context of 4 ongoing clinical studies involving individuals with an ACL injury, meniscus tear or OA. The specific aims of this application are to: 1) evaluate the appropriateness of the items in the pain interference and physical function item banks; 2) provide evidence for interpretation and use of the pain interference and physical function CATs; 3) investigate differential item function (DIF) and 4) determine the efficiencies gained by use of the PROMIS pain interference and physical function CATs in comparison to legacy fixed-length PRO measures for the knee. Up to 50 subjects from the parent studies will participate in cognitive interviews to determine the clarity and relevance of the items and to identify any gaps in domain content coverage. Up to 600 individuals from the parent studies will be followed longitudinally to determine test re-test reliability, responsiveness and the patient acceptable symptom state. Item responses will be explored to identify potential sources of DIF including age, gender and type of knee condition. Efficiency will be assessed by comparing time for administration as well as reliability and responsiveness of the CAT versus the fixed-length legacy PRO measures. The results of this study will provide validity evidence to support interpretation and use of the PROMIS pain interference and physical function item banks and CATs in individuals with a variety of common knee conditions including ACL injury, meniscus tear or OA.