Osteoarthritis (OA), the most common form of arthritis, is a progressive disorder characterized by gradual loss of cartilage and the development of bony spurs and cysts at the surface and margins of the joints. Inflammation, pain, stiffness, limited movement, and possible deformity of the joint may result. Treatments for OA aim to reduce or control pain, improve physical function, prevent disability, and enhance quality of life-all of which constitute clinical outcomes of importance to patients. Treatment options include pain relievers, anti-inflammatory drugs, weight loss, general physical exercise, PT, and, when conservative treatments fail, surgery. This Future Research Needs (FRN) project is a follow up to the draft Comparative Effectiveness Review "Physical Therapy Interventions for Knee Pain Secondary to Osteoarthritis (OA)." The review was motivated by uncertainty around the effectiveness and comparative effectiveness of physical therapy (PT) treatments for adult patients with knee pain secondary to osteoarthritis (OA). FRN projects identify gaps in the current research that limit the conclusions in CERs and inform those who conduct and fund research of these gaps. FRN projects aim to encourage research likely to fill gaps and make the body of evidence more useful to decisionmakers. The report addressed the following Key Questions (KQs): KQ 1: What are the effectiveness and comparative effectiveness of available PT interventions (without drug treatment) for adult patients with chronic knee pain due to OA on intermediate and patient-centered outcomes when compared with no active treatment or another active PT modality? a. Which patient characteristics are associated with the benefits of examined interventions of PT on intermediate and patient-centered outcomes? b. Do changes in intermediate and patient-centered outcomes differ by the dose, duration, intensity, and frequency of examined interventions of PT? c. Do changes in intermediate and patient-centered outcomes differ by the time of follow up? KQ 2: What is the association between changes in intermediate outcomes with changes in patient-centered outcomes after PT interventions? a. What is the validity of the tests and measures used to determine intermediate outcomes of PT on OA in association with patient-centered outcomes? b. Which intermediate outcomes meet the criteria of surrogates for patient-centered outcomes? c. What are minimal clinically important differences (MCIDs) of the tests and measures used to determine intermediate outcomes? KQ 3: What are the harms from PT interventions available for adult patients with chronic knee pain due to OA when compared with no active treatment or active controls? a. Which patient characteristics are associated with the harms of examined PT interventions? b. Do harms differ by the duration of the treatment and time of follow up? The review was motivated by uncertainty around the effectiveness and comparative effectiveness of physical therapy (PT) treatments for adult patients with knee pain secondary to osteoarthritis (OA). The purpose of this FRN project is to identify and prioritize specific gaps in the current literature on PT for knee pain due to OA that would aid decisionmakers. We used a deliberative process to identify evidence gaps, translate gaps into researchable questions, and solicit stakeholder opinion on the importance of research questions. This report proposes specific research needs along with research design considerations that may be useful in advancing the field.