A continuous passive motion (CPM) is a machine designed to help patients regain joint movement after a surgical procedure. The knee joint needs motion for its healthy function. A joint which is not moving for an extended period may become stiff. Many patients may experience knee stiffness after knee surgeries like total knee replacement or ACL (Anterior Cruciate Ligament) reconstruction due to non-movement.

A knee CPM machine passively extends and bends the knee joint to maintain motion. The device not only keeps the joint from becoming stiff but also increases the range of motion. The machine works passively, i.e., the patient does not need to extend or bend the knee themselves. The device works to extend or bend the knee.

The physicians typically advise a CPM machine and physical therapy to increase knee joint motion after the surgery. Knee stiffness is a common complication after knee surgery as scar tissue tends to build if the joint is not moved after the surgery. The scar tissue may toughen as more time passes by, leading to a stiff knee joint with a reduced motion range.

Apart from preventing knee stiffness after knee replacement surgery, the CPM machine forms an essential part of treatment after surgeries are done to remove knee adhesions or contractures. The device has motorized parts holstered to the joint and slowly moves the joint at a fixed speed and to the range of motion advised.

The CPM machines also gently exercise the muscles around the knee to help regain strength. The pain and swelling associated with the surgery also get better sooner due to the joint’s motion, improving the circulation to the tissues around the joint.

Video demonstrating the knee CPM machine.

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Dr. Suhirad Khokhar

My name is Dr. Suhirad Khokhar, and am an orthopaedic surgeon. I completed my MBBS (Bachelor of Medicine & Bachelor of Surgery) at Govt. Medical College, Patiala, India.

I specialize in musculoskeletal disorders and their management, and have personally approved of and written this content.

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