Hi Joe,
Have you had the same sharp pain behind the kneecap since the surgery, or has it come on in the last few weeks of PT? Does your PT person have an idea what factors might be causing that specific location to hurt, and does any sort of massage or manipulation help at all, even temporarily? If nothing improves in a week or two, I would probably try to see the doctor, or maybe consider a new physical therapist if the doctor sees no problem.

Each TRK can be different. My 2nd TKR flexion range is just slightly under that of the first TKR. It may be because that leg was straightened a bit because I was getting so pidgeon-toed due to my knee pain so surgery was a bit different. Or maybe I had such good results on the first one that I took the whole PT process more lightly and did not press myself as hard at home after PT was over for the 2nd.