Continuous Passive Motion (CPM) Therapy

Continuous Passive Motion (CPM) Therapy

Continuous Passive Motion (CPM) Therapy Experimental investigations in the 1970s provided the scientific basis for CPM treatment using motor-driven exercise equipment. Positive clinical experience, with this exciting therapeutic modality being well received by surgeons, therapists and patients, accelerated its widespread acceptance. Twenty-five years later, advances in technology and the extension of this form of post-surgical rehabilitation therapy to new indications and protocols demonstrate that CPM still plays an integral and significant role in orthopaedic recovery. For the patient, it is a valuable and well-tolerated method of rapidly restoring lost joint function, mobility and confidence.

It is important to review the key clinical outcomes from Professor Robert Salter’s pioneering animal work. He used rabbits with the following pathologies:

  • Full thickness cartilage defects
  • Acute septic arthritis
  • Intra-articular fractures
  • Partial thickness tendon lacerations

Rabbits with full thickness cartilage defects were divided into three treatment groups with therapy instituted immediately postoperatively as follows:

  • Immobilisation with a cast
  • Intermittent active motion (cage activity)
  • Continuous passive motion


  • The immobilised group showed healing characterised by the formation of fibrous tissue and many joint adhesions.
  • The cage activity group showed imperfect healing characterised by a combination of fibrous tissue and poorly differentiated cartilage.
  • The CPM group showed healing through formation of new hyaline-like cartilage occurring in one half of the defects within four weeks. CPM did not harm intact, normal living articular cartilage in rabbits.