The objective of this study was to capture and analyze the kinetics and kinematics and determine the functional performance of the osteoarthritic knee after a posterior cruciate ligament (PCL) retaining total knee arthroplasty. Kinematic and kinetic gait analysis of level walking was performed in 20 subjects (12 female and 8 male) with knee ostoarthritis. These patients were free of any neurological diseases that could affect their normal gait. Mean age was 69.6 ± 6.6 years; mean height was 157.6 cm ± 7.6 cm; and mean weight was 77.2 ± 12.1 kg. Full body gait analyses were performed using the BIOKIN 3D motion analysis system before and 9 months after total knee arthroplasty procedures. Single-step ascending kinetic analyses and plantar pressure distribution analyses were also performed for all subjects. International Knee Society Scores (IKSSs) were also assessed pre- and postoperatively. Significant increases were noted postoperatively in average cadence (preoperative mean = 99.26, postoperative mean = 110.5; p < 0.004), step length (preoperative mean = 0.49, postoperative mean = 0.54; p < 0.01) , and walking velocity (preoperative mean = 0.78, preoperatively, postoperative mean = 0.99; p < 0.001). Decreases in stance duration percentage and knee adduction moment were also reported postoperatively. All patients showed a significant improvement of knee kinetics and kinematics after a PCL retaining total knee arthroplasty. Significant differences were found in the cadence, step length, stride length, and walk velocity postoperatively. IKSSs also significantly improved. Further research is warranted to determine the clinical relevance of these findings.