The joint range of motion tester is a testing device specifically designed for patients with impaired joint movement functions. Based on the theories of rehabilitation medicine and sports medicine, this instrument can accurately measure the maximum angle of joint movement, which is known as the range of motion (ROM). By obtaining accurate data on joint range of motion, the tester helps therapists assess the patient's rehabilitation progress, develop personalized rehabilitation plans, and track treatment outcomes. It is crucial for diagnosing joint diseases, improving joint flexibility, and enhancing musculoskeletal functions.