The biologic concept of continuous passive motion of synovial joints. The first 18 years of basic research and its clinical application.

The notoriously limited capacity of articular cartilage to heal or to regenerate plus the author's clinical observations and research on the deleterious effects of immobilization on joints led him to the biologic concept of continuous passive motion (CPM) of synovial joints in 1970. The hypothesis that CPM should stimulate pluripotential mesenchymal cells to differentiate into articular cartilage and should accelerate the healing of articular tissues has been validated by numerous scientific investigations of a variety of experimental models of the knee joint. These models have included full-thickness defects, intraarticular fractures, acute septic arthritis, partial thickness lacerations of the patellar tendon, semitendinosus tenodesis to replace the medial collateral ligament, autogeneic osteoperiosteal grafts in major defects, free autogeneic periosteal grafts, and periosteal allografts. In 1978, the author collaborated with Saringer, an engineer, to develop CPM devices for humans. CPM is clinically indicated following such procedures as open reduction of fractures, arthrolysis for posttraumatic arthritis, synovectomy, drainage of septic arthritis, release of joint contractures, total arthroplasty, tendon repair, and ligament reconstruction. Clinically, CPM is an important stimulus to joint regeneration processes.