Total knee arthroplasty (TKA) has been shown to be one of the most successful operations performed to restore function, relieve pain, and improve quality of life in patients with severe arthritis of the knee. The primary physical therapy goals after TKA are unassisted transfers, walker ambulation, cane ambulation, unassisted stair negotiation, and active knee flexion to 90[degrees]. Functional progression may be influenced by many factors including type of prosthesis used. The purpose of this study was to compare the differences in achievement of specific functional milestones (FMs) in patients who received posterior cruciate ligament (PCL)-retaining prosthesis and those who received posterior-stabilized (PS) prosthesis. The PCL is the primary stabilizer of the knee that prevents posterior tibial translation. It is a secondary stabilizer of the knee for varus and valgus stress. Sixty-eight consecutive patients with osteoarthritis of the knee underwent unilateral TKA by a single surgeon. There were 20 males and 48 females ranging in age from 34 to 85 with a mean age of 69.7 years. There were 42 patients in the PCL group and 26 patients in the PS group. Components used were as follows: femur-cemented Genesis with or without PS module, tibia-cemented Genesis with or without PS module, and patella-cemented Genesis biconvex. Physical therapy protocol was the same for both groups. Physical therapists were blinded toward prosthesis selection. The following unassisted FMs were monitored on a valid and reliable functional milestone form: transfers, walker ambulation, cane ambulation, stair negotiation, active knee flexion to 90[degrees], and postoperative day of discharge. Independent t tests, corrected for multiple measures, were used to compare these groups. There were no significant differences between the groups for postoperative day of achievement of unassisted transfer, walker ambulation, cane ambulation, stair negotiation, and discharge; however, there was a significant difference between groups for active range of motion at discharge, P = .03. Although the difference was significant, it was not clinically significant.