The investigators aim to explore the effects of action observation therapy on pain and brain hemodynamics in patients with knee osteoarthritis. This study will create a new perspective to understand the physiology of pain, by applying painful stimulation during the neuroimaging system which has attracted much interest in the literature in recent years, and will shed light on the studies that can be done in this regard. Participants' pain level will be assessed using Visual Analog Scale and pressure algometer. Also joint range of motion in the initial assessments will be measured by electro-goniometer, muscle strength assessment by JTech hand dynamometer at appropriate evaluation positions. Fear of movement of individuals will be assessed via Tampa Kinesiophobia Scale and functional levels will be assessed via Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Timed Up and Go Test. Functional near infrared spectroscopy (fNIRS) will be used for evaluation of brain hemodynamics. The first group, will receive exercises with action observation therapy; and the second group will receive only exercises. The exercise programme will be administered under physiotherapist supervision for three days a week for six weeks. The evaluations will be repeated at the beginning of the study and at the end of the sixth week. Data obtained from the study will be analyzed using appropriate statistical methods.

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.

The investigators aim to explore the effects of action observation therapy on pain and brain hemodynamics in patients with knee osteoarthritis. This study will create a new perspective to understand the physiology of pain, by applying painful stimulation during the neuroimaging system which has attracted much interest in the literature in recent years, and will shed light on the studies that can be done in this regard. Participants' pain level will be assessed using Visual Analog Scale and pressure algometer. Also joint range of motion in the initial assessments will be measured by electro-goniometer, muscle strength assessment by JTech hand dynamometer at appropriate evaluation positions.Fear of movement of individuals will be assessed via Tampa Kinesiophobia Scale and functional levels will be assessed via Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Timed Up and Go Test. Functional near infrared spectroscopy (fNIRS) will be used for evaluation of brain hemodynamics. The first group, will receive exercises with action observation therapy; and the second group will receive only exercises. The exercise programme will be administered under physiotherapist supervision for three days a week for six weeks. The evaluations will be repeated at the beginning of the study and at the end of the sixth week. Data obtained from the study will be analyzed using appropriate statistical methods.

Inclusion Criteria:

• MMSE>21
• Chronic knee pain (VAS score>5)
• Right dominant
• Unilateral knee pain

Exclusion Criteria:

• Pain characteristics such as the presence of a rheumatologic disease other than knee osteoarthritis, lumbar radiculopathy, systemic inflammatory disease, diabetic neuropathy, problems similar to knee osteoarthritis,
• Hearing or vision problems,
• Injection therapy involving the knee region within the last 6 months,
• Surgical operation involving the knee region
• Psychiatric problems and anti-depressant usage