Highly porous surfaces promoting biologic fixation have renewed interest in cementless total knee arthroplasty (TKA), but the potential for failed biologic fixation remains. The purpose of this study was to compare the clinical outcomes of cemented and cementless versions of the same TKA design at an average of 2 years postoperatively.Methods:This was an institutional review board-approved, prospective, randomized controlled trial of patients from 18 to 75 years of age who were undergoing a primary TKA. Patients with inflammatory arthritis, a body mass index (BMI) of >40 kg/m2, infection, a neuromuscular disorder, or grossly osteoporotic bone or bone defects were excluded. Patients were randomized to receive a cemented or cementless cruciate-retaining TKA of the same design. The cementless implant has highly porous fixation surfaces. Oxford Knee, Knee Society, and Forgotten Joint Scores were collected. Patients were asked to rate the knee with the TKA as a percentage of normal. Power analysis indicated that 130 patients were necessary to demonstrate a 5-point difference in the Oxford Knee Score at 90% power.Results:One hundred and forty-seven patients were enrolled, and 141 (96%) of them were analyzed at an average of 2 years postoperatively. There was no difference in age, sex, BMI, American Society of Anesthesiologists (ASA) score, or duration of follow-up (p = 0.1 to 0.9). There was also no difference in the change in the hemoglobin level from the preoperative measurement to postoperative day 1 between the 2 cohorts (mean and standard deviation, -2.6 ± 1.4 g/dL compared with -2.5 ± 0.9 g/dL, p = 0.5), but the total operative time was decreased in the cementless cohort (82.1 ± 16.6 compared with 93.7 ± 16.7 minutes, p = 0.001). There were no differences in any clinical outcome measure at 4 to 6 weeks, 1 year, or an average of 2 years postoperatively (p = 0.1 to 0.9) between the cemented and cementless cohorts. There was no radiographic evidence of component subsidence or loosening in either cohort.Conclusions:This study demonstrated that a recently introduced cementless TKA had results, both perioperatively and at an average of 2 years postoperatively, that were equivalent to those of its cemented predecessor, without any aseptic failures of either implant. Thus, this study justifies continued surveillance of this device to elucidate both its survivorship and if it can provide any long-term benefits.Level of Evidence:Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.