Can a knee replacement surgery help treat patellofemoral syndrome or chondromalacia patella?

Yes,but: Knee replacement should be reserved (in my non-orthopedic) opinion for severe knee disease-not the 2 conditions you mentioned.

Last restort : Chondromalacia patella (runners knee) is due to overload of the patellofemoral joint (knee cap against the end of the thigh bone). Running causes high forces in this portion of the joint. So does arising from a chair, going up/down stairs. Treatment consists of activity modification, ice, anti-inflammatory meds and therapy aimed at flexibility and strengthening, especially of your core.