A repetitive motion therapy apparatus has a frame structure. An orthotic is adapted for securing to a part of a body. A pneumatic muscle is coupled between the frame structure and the orthotic for moving the orthotic. A control mechanism controls the pneumatic muscle. The pneumatic muscle contracts to impart movement to the orthotic. A winding spool and retractable cord is attached to the pneumatic muscle. The pneumatic muscle is operated by an electric mechanism, hydraulic mechanism, or spring mechanism to impart movement to the orthotic. The control mechanism has a variable airflow controller to control the movement of the orthotic. A feedback sensor is disposed on the body for providing data to the control mechanism. A treadmill imparts motion to the part of the body.