The objective of the current study was to compare kinematic patterns of anterior cruciate retaining total knee arthroplasty and posterior stabilized total knee arthroplasty. Fifteen patients received an anterior cruciate retaining total knee arthroplasty and 15 received a posterior stabilized total knee arthroplasty. All total knee arthroplasties were clinically successful (Hospital for Special Surgery score > 90). Each patient was examined during level walking using fluoroscopy. Femorotibial contact paths for the medial and lateral condyles were determined using a computer automated model-fitting technique. Ten of 15 (67%) patients receiving an anterior cruciate retaining total knee arthroplasty and 12 of 15 patients (80%) receiving a posterior stabilized total knee arthroplasty experienced anterior contact at some phase of the gait cycle. Anterior contact in anterior cruciate retaining total knee arthroplasty can be attributed to the presence of the anterior cruciate ligament, resisting the anterior tibial shear forces during gait. The reason for anterior contact observed in posterior stabilized total knee arthroplasty is unclear, possibly related to the sagittal topography (dwell-point position) of the tibial component. Increased axial rotation was seen in anterior cruciate retaining total knee arthroplasty possibly because of the preservation of the four-bar linkage within the knee. Patients receiving an anterior cruciate retaining total knee arthroplasty experienced kinematic patterns more similar to the normal knee.