Scenario: Mr. Patel recently had a total knee replacement. Nurse Davis is explaining the use of a device that moves his knee through a complete range of motion without requiring him to actively move the joint. Which type of exercise is Mr. Patel performing with this device?

Continuous passive motion (CPM) is a post-surgical rehabilitation technique in which a mechanical device moves a joint — most commonly the knee after total joint replacement — through a prescribed range of motion without requiring active muscular effort from the patient. The device is programmed to flex and extend the joint continuously, which promotes cartilage nutrition, reduces postoperative stiffness, and may help decrease edema and pain in the early recovery period. Because the machine performs the movement, this is classified as passive exercise, distinguishing it from all forms of active exercise. Active isotonic exercises such as walking or lifting weights require the patient to voluntarily contract muscles and move their own joints, which is not occurring here. Aerobic exercises like jogging or swimming demand sustained cardiovascular effort and active participation, making them entirely different from what is described. Stretching exercises performed independently also require the patient's own muscular and volitional effort. The defining characteristic in the scenario — the device moves the knee without the patient actively participating — is the hallmark of continuous passive motion, making it the correct answer.