Continuous Passive Motion Machine , is a device that is used to gently flex and extend the knee joint. These machine can be used after surgery to allow the knee joint to slowly bend. The initial thought was these machine would improve motion following knee replacement surgery, as well as other knee procedures, and eliminate the problem of stiffness, By placing the knee in this device soon after surgery, scar tissue would not develop, and the problem of stiffness would not be a concern.​