A, With loss of posterior condylar offset and roll forward of femoral component on tibial tray, there can be limited flexion from abutment of posterior femur against polyethylene insert. B, With proper posterior femoral offset and functioning posterior cruciate ligament (PCL), flexion can be optimized without impingement of posterior aspect of femur against tibial insert. C, A posterior stabilized implant with post and cam drives rollback of femoral condyles on tibial tray, optimizing flexion. D, In this radiograph an example of posterior-stabilized TKA shows optimal flexion with complete support of posterior condyles and no edge loading on posterior lip of polyethylene.