Horse lame after exercise

Question
I have a 7 year old TB gelding who recently went lame in his off fore. I went up the field to feed him one night about a month ago and he was lame. His whole foreleg was swollen (from knee to fetlock down his tendon) so I brought him in and hosed the leg. I kept him in for 2 days and the swelling went down dramatically and he was sound by the Saturday when I trotted him up. I took him out on the Sat. and he stayed sound but when I went to do the night feeds he was lame again. I left him out and the following day he was sound. I left him a week and he stayed sound but when I took him out the following week he was lame again, this time straight after exercise. Again the following day he was sound. I have now rested him for 3 weeks and am going to ride him out again on Sunday. He has been sound the full 3 weeks but still has a small amount of swelling at the bottom of his tendon at the back of the fetlock, not unlike a windgall, which got slightly worse when the farrier had been. The farrier checked for and discounted a punctured foot though was also a but "ouchy" when the nails were put in, as if the vibrations were causing him pain. He does not respond to hard pinching of the area, or manipulation of the fetlock joint.

I am at a loss as to what can be wrong, the vet is coming out to do vaccs in a week or so so will be getting him to check him out then but would appreciate some advice in the meantime.

Thanks

Answer
Hi Jo.
  I've been thinking and thinking and just can't think of an injury that would mimic the soundness/lameness pattern you describe. Normally I would suggest hosing the leg, maaybe using some ice boots and feeding an anti-inflammatory, but that would make the vet's work more difficult.
  Best of luck getting to the bottom of this and please let me know what the problem turns out to be. Sorry I couldn't be of more assistance.
Anne Stepien