A randomised, controlled study of the use of postoperative continuous passive motion (CPM) and immobilisation regimen after total condylar knee arthroplasty was performed. CPM resulted in a significant increase in both the early and late range of knee flexion. This increase occurred in both rheumatoid and osteoarthritic patients. The improvement of 10 degrees at 12 months allowed additional important function to be attained. CPM resulted in significantly earlier discharge from hospital. It did not increase the clinical incidence of wound healing problems, nor did it significantly increase the postoperative fixed flexion deformity or the extension lag. CPM can be recommended as a safe and effective modality to achieve more rapid and more successful postoperative rehabilitation after knee arthroplasty.