Which of the following is a primary use of a CPM machine?

• A. Increase active ROM beyond what is safe
• B. Control post op pain, reduce inflammation, provide PROM, and protect the healing tissue
• C. Replace manual therapy
• D. Speed up tissue dehydration

Answer: (B)

Continuous passive motion devices are used after surgery to promote controlled joint movement while protecting the healing tissues. The main purpose is to help manage postoperative pain, reduce swelling and inflammation, and provide a passive range of motion within a safe, surgeon-prescribed limit. Because the movement is produced by the machine rather than by the patient actively contracting muscles, the tissue receives gentle mobilization without stressing repaired structures, which helps prevent stiffness and contractures during the early healing phase.

This approach is not aimed at increasing active ROM or strength, since the patient isn’t actively moving the joint. It also doesn’t replace hands-on manual therapy, which includes manual joint mobilizations and soft tissue work tailored to the patient. And it isn’t about drying out tissues; the goal is to minimize swelling and support healing through improved circulation and joint nutrition.