From what I have read...you know very quickly if the block helped with the pain. Sometimes the relief is VERY short (maybe only a couple of hours) and sometimes it will last days, weeks, or even months. It may also be that the first one doesn't help much or at all...but if you do a series of them then you get relief and the relief lasts longer. Any sort of relief at all can be a very good sign.

Also be aware that some doctors will put you out for the procedure, some will keep you awake. Some will use fluoroscopy so they can pinpoint EXACTLY where they are putting the needle and other won't. If the first one "works" in that you see the foot turning deep red and getting warm but no relief, then it could be that the doc didn't get the exact right placement for the block and it's worth trying again and adjusting the location a bit.

Good luck and take care.