Summary:Many authors recommend early knee manipulation in stiff total knee arthroplasty. Recurrent loss of motion may occur when manipulation is performed early. The main factors in the development of stiffness are adhesion and scar formation, and delayed manipulation after scar maturation may prevent resultant loss of motion. The authors compared 23 osteoarthritic knees that received postoperative manipulation before 3 months (group 1) with 23 osteoarthritic knees that received postoperative manipulation beyond 3 months (group 2). Demographic data for both groups were similar. The follow up ranged from 2–15 years postoperatively. Preoperative flexion values for groups 1 and 2 were 101.0° and 100.4°, respectively. Premanipulation flexion values for groups 1 and 2 were 64.6° and 64.6°, respectively. Postmanipulation flexion values for groups 1 and 2 were 110.0° and 108.9°, respectively. Final flexion values for groups 1 and 2 were 110.0° and 108.3°, respectively. There was no significant difference for final flexion in the two groups. Thirteen (61%) heterotopic ossification lesions were found in group 1, but three knees (13%) had heterotopic ossification in the premanipulation period; three (13%) Pellegrini-Stieda lesions in the premanipulation period and three (13%) heterotopic ossification lesions in the postmanipulation period were found in group 2.