The posterior stabilized (PS) knee has a satisfactory long-term postoperative survival rate, and recently, with the rejuvenation of patients and lifestyle differences, the restoration of normal kinematics and highly functional movements has become highly desirable for patients. However, there are significant differences between the kinematics of the prosthetic knee and the normal knee. In particular, the amount of tibiofemoral axial rotation and the amount of femoral posterior displacement are both significantly deficient. The factors that influence the motion of the tibiofemoral joint include component design and peripheral soft tissue function. The cam-convex pile mechanism of the PS-type knee joint has been shown to guide joint motion, and its form can be characterized as either planar or curved contact. In addition, the modification of the lateral collateral ligament function by adjusting the position of the articular surface should also influence the knee joint tightness and thus change its motion pattern. Therefore, the purpose of this study was to evaluate the kinematic effects of different cam-convex pile mechanism features and to analyze the changes in the function of the collateral ligaments after the variation of the joint surface position using a dynamic knee model. In this study, a planar contact type and a curved contact type cam-convex pile mechanism were used to model the artificial knee joint, and the knee joint was driven to bend through the center of the femoral condyle to form the axis of rotation. The percentage change of the attachment point of the lateral collateral ligaments during full extension to 135 degrees of knee flexion was calculated to compare the effect of joint surface position variation on ligament function. It was found that at the maximum bending angle (135 degrees), the internal rotation of the tibia was 4.9 degrees for the curved contact design and only 0.9 degrees for the flat contact design. In terms of variation in articular surface position, increasing the articular surface increased the ligament attachment point distance with knee flexion, with a maximum increase of 18.1% and 7.4% for the medial and lateral collateral ligaments, respectively; conversely, decreasing the articular surface further reduced the length of the medial and lateral collateral ligaments by 20.5% and 6.0%. This study confirms that the cam-convex pile design with curved contact provides smoother tibiofemoral axial motion and improves tibial internal rotation during high knee flexion compared to the planar contact design. If a clinician is faced with severe knee deformity resulting in excessive laxity of the lateral collateral ligaments, a higher articular surface position may be considered to help maintain knee stability.