Osteoarthritis is a degenerative joint disease associated with pain and disability that occurs in 25% of the population over 18 years of age Worldwide. It is expected that osteoarthritis will be the fourth most common cause of disability in the World by 2020. Osteoarthritic joint has pathological changes such as damage of joint cartilage tissue, thickening of the subchondral bone, osteophyte formation, inflammation of synovium at different levels, degeneration of ligaments and meniscal structures and hypertrophy of joint capsule. Pain is the most common symptom in osteoarthritic patients and the ongoing pain effects quality of life and physical functions of them negatively. At the same time, decrease in joint range of motion, muscle strength loss and decline in functional level may go along with pain. In recent years, studies that relate chronic pain to neuroplasticity have demonstrated changes in the structure, function and somatotopic organization of the primary motor and sensory cortex of osteoarthritis patients with chronic pain. In addition to this, osteoarthritis studies showed that the pain does not originate solely from joint problems; the central nervous system is also responsible for the formation of pain sensation. Changes in the cortical sensorimotor areas include sensory disturbances, perceptual problems (differentiation of body image), and motor influences, and these changes are associated with severity and duration of pain. It is reported that approaches targeting cortical reorganization resulted in decreased pain and increased function. Action observation therapy is a method which activates mirror neurons and is applied to learn a specific motor skill, facilitate motor learning and decrease the pain level of the extremities. It is anticipated that action observation therapy may differentiate perception of pain by altering cortical activity and thus altered motor cortical activity may play an active role in reducing pain by modulating pain-related neural networks.