Suspension therapy uses specialized equipment to provide passive and assisted exercises for various joints. There are three main types of suspension - axial, pendular, and vertical - which differ based on where the supporting hook is placed in relation to the joint and center of gravity. The suspension unit was invented and consists of fixed points, supporting ropes, slings, and other attachments to position the patient for passive range of motion exercises of shoulders, elbows, hips, knees, and ankles. Suspension therapy provides advantages over other methods like continuous passive motion by allowing resistance to be added to muscle work as needed.