This study is an uncontrolled intervention study with repeated measures. The intervention is a 12-week supervised exercise class featuring biomechanically sound exercises for people with knee osteoarthritis. Measures of strength of the knee muscles, pain, biomechanics during walking and yoga, mobility and cardiovascular health will be included. Strength will be measured on a dynamometer. Pain will be assessed with questionnaires. Walking and three yoga postures will be observed using motion capture system integrated with force measurements from the floor. Mobility will be assessed during walking, stair-climbing and chair standing tasks. Cardiovascular health will be measured during a submaximal bicycle task.