Stretching hams may be good if they are tight. But for this kind of knee pain a quad stretch is probably in order plus the calves and iliotibial band (just rolls off my keyboard
). Step ups help to get the VMO which helps keep the knee cap moving in line and not being pulled to one side so that is very helful. And step ups are just cool anyway. Try to go at with the platform or whatever being at a height that gets your thigh about parallel. That'll give you a pretty neutral affect in terms of hams/quads but will still do the quad thing (VMO).