Continuous Passive Motion

Continuous Passive Motion is the application of passive motion via a motorized device.  Originally proposed by Dr. Robert Salter of Canada to assist in the healing of synovial joints.  He hypothezised that the application of CPM would be benificial for 3 reasons:

  1. Nutrition and metabolic activity of articular cartilage would be enhanced
  2. Articular cartilage regrowth would be achieved by stimulating tissue remodeling
  3. Healing of articular cartilage, tendons, and ligaments would be accelerated

There are two main types of CPM devices but a wide variety of different models designed for different body parts.  The two main types of CPM are:

  1. Anatomical - Moves the joint in a manner similar to the natural motion of the joint.
  2. Free Linkage - Allows motion in the structures adjacent to the joint, thus allowing the limb to seek its own anatomical motion.

Physiological effects of CPM

  • Enhance and facilitate connective tissue strength, size and shape.
  • Evacuate joint hemarthrosis - bloody effusion within the joint space - reduce joint swelling.
  • Improve joint nutrition.
  • Inhibit adhesions.
  • Initiate normal joint kinematics.
  • Reduce articular surface changes.
  • Minimize other deleterious effects of prolonged immobilization.

Indications for the use of CPM

  • Orthopedic, musculoskeletal injuries
  • Open reduction, internal fixation (ORIF) of an intra-articular fracture when fracture fragments are stable
  • Postdiaphyseal and metaphyseal fractures
  • Capsulotomy and arthrolysis
  • Arthroplasty
  • Ligament reconstruction
  • Synovectomy
  • Arthrotomy
  • Drainage of acute specific arthritis (after incision and drainage and pharmaceutical management)
  • Tendon reconstruction
  • Burns

Contraindications and Precautions to be aware of before initiating CPM

  • Unstable fractures
  • Active infection
  • Fused joints
  • Hemophilia or blood-thinning medications
  • Renal failure
  • Proper positioning, alignment, and monitoring
  • Claustrophobia
  • External fixation devices

Protocols for the delivery of CPM can range anywhere from 24 hours a day for as long as a month to as little as 6 hours a day after surgery.  A lot will depend on patient comfort as well the surgical procedure performed and the body structures involved.  Usually the first 3 weeks after injury or surgery offer a window when CPM favorably influence biologic tissue healing.

It should be noted that written instructions and verbal communication about the use of the CPM device should be given to the patient and/or family caretake or nursing personnel. 

The following guidelines are for a short-term treatment (i.e. less than 24 hours).

  1. Can use Cpm when patient is wearing a brace or surgical bandages.
  2. Measure length of patientís thigh from ischial tuberosity to joint line. Adjust
    proximal carriage so proximal end meet the bottom of the buttocks.
  3. Measure length of patientís lower leg from joint line of knee to approximately
    0.25 inch below heel. Adjust distal portion of carriage accordingly.
  4. Place patientís lower extremity in unit. Joint line of knee should match articular
    hinge of CPM unit.
  5. Adjust foot in foot plate so that tibia is placed in neutral position. Internally or
    externally rotating tibia can result in increased stress being placed on ACL, for
  6. Set range of motion as prescribed by physician. Generally patient is started with
    a low ROM and progresses to full range of motion as healing occurs.
  7. Set speed of treatment. Most acute users begin therapy at 1 cycle per minute.
    Speed of movement is then increased to patientís tolerance.
  8. Give patient interrupt control and provide instruction on
    how and when to use it.

Below are some of the different models used in the delivery of CPM

This is a shoulder CPM unit.
This is a knee CPM unit.
This is an elbow CPM unit.
This is an ankle CPM unit.