The kinematics of the knee are so complex. You can not overlook the PFJ. We are taught early on about medializing the button and lateralize the femur and make sure your femoral rotation is correct. If not you are taught to do a lateral release.
The balancing of the PFJ is so important. Overstuff it and you have pain and limited range of motion. Too loose and you lose efficiency of the extensor mechanism.
Here I will share some tips and my thoughts on what I look for when I do a TKA specifically focusing on the PFJ.