Tibiofemoral osteoarthritis (TFOA) is highly prevalent in older adults, and often causes symptoms and functional limitations. Physical activity is widely advocated in people with TFOA, and running is an easy and accessible activity that provides many benefits on general health. However, running induces high knee loads, which could potentially contribute to symptoms of runners with TFOA. Previous studies have suggested that running gait modifications can help in decreasing symptoms and knee loading in runners with knee conditions. Yet, no study has been conducted in runners with TFOA. This intervention study will investigate the effects of a 4-week running gait retraining program on symptoms and running biomechanics in runners with TFOA. We hypothesize that running modifications will decrease symptoms, improve function and reduce knee loading.