In posterior-stabilized total knee arthroplasties, a femoral cam and polyethylene tibial post are commonly used to restore posterior stability after sacrifice of the posterior cruciate ligament. This article reports a high incidence of early tibial post failures in one design of prosthesis and examines the variables that may have contributed to such. Five hundred sixty-four consecutive posterior-stabilized total knees were implanted in 512 patients, using a total knee prosthesis with a polyethylene tibial post and femoral cam. Clinical and radiographic outcomes were measured at a mean follow-up of 40 months after surgery (range, 24-83 months). At follow-up, 70 knees in 62 patients (12%) had undergone revision surgery because of symptoms related to catastrophic failure of the tibial post.