I wonder if this is an issue for me. I had three operations on my left knee - initial TKR and two revisions to try to correct instability due to lax ligaments in front of my knee. The last Operation left me with numbness and cold feelings in my left foot. by, Drs seems confused and the only idea seems to be that it's nerve issues coming from my back. I'm not so sure. Maybe I should try to get some doc to order this test for me. I don't get purple coloring in my foot - just numb and cold in my toes, particularly after standing and walking - and it doesn't take much. I'm really in a bad mental state. I've been through SO MUCH with this left leg. IT all happened after TKRs and subsequent surgeries, I don't want any more surgeries but i really want my ability to walk and stand with out losing feeling in my foot! thanks.