Hi fishtaco

Thanks for the info on your exercise programme - Sounds all good to me. No real suggestions there.

So standing on one leg and bending forward brings the symptom on - could possibly be adverse neural tension of the sciatic nerve. Adverse neural tension can masquerade as hamstrings injury quite easily. Neural pain can be dramatic too which might explain the severity of the pain The diagnostic test for this is called the slump test - you could check if your PT did this. The cause of adverse neural tension is usually some sort of impingement along the course of the nerve: the back, piriformis or could be something going on at the back of the knee. If it is this then the treatment is mobilisation of the nerve.

Other then that I can't think of what else it might be.