RecruitingPhase 3Behavioural interventionRehabilitation for Arthritis of The Knee: mainTaining Improvement for VeteransThe aims are to determine whether 1) an incentive based on behaviorally-enhanced gamification and social incentives and 2) health coaching can promote adherence to exercise and physical activity after physical therapy for osteoarthritis of the knee (KOA). The research design is a randomized clinical trial with factorial design This randomized clinical trial of 254 patients using a factorial design will leverage a clinical trial platform developed through the University of Pennsylvania that allows for the remotely capture important patient-reported outcomes and other interaction through a participant's smart phone. The investigators will randomize participants to receive social incentives with gamification to promote adherence to prescribed exercises as well as maintenance of greater levels of physical activity and compare to controls that receive a Fitbit but no additional incentive. Participants may also be randomized to receive a health coach. The investigators will utilize mobile applications for smart phones and wearable activity trackers through the Way-to-Health platform and assess, in real time, the impact of the interventions on patient-reported function and pain (as measured by the Knee Osteoarthritis Outcome Score) as well as physical activity. Participants will be followed for 2 years, with a total of 5 in-person visits. Knee osteoarthritis (KOA) is one of the most prevalent and disabling conditions among Veterans and accounts for high morbidity and high costs for the VA. Importantly, while physical therapy is valuable for patients with KOA, lack of adherence to home exercises and low overall physical activity limit the durability of response. The current proposal aims to address two important knowledge gaps in the management of KOA in order to improve pain and function.