Strange swelling

[opgr1234]

My boy has had a strange swelling for past 4 days. Just wondering if anyone has had similar or can shed any light.

Its on the inside of his near hind, and began as a slightly puffy swelling from his chestnut about half way down to his fetlock. To be honest if you didnt know his legs you may not have noticed, but the definition had gone and it was slightly warm. then it moved round the back of his leg, so that it was visible when looking at him from the side. I hope this is making sense, hard to explain! now its a triangle shaped swelling pointing down and round the back of his tendon, still only extending about halfway down to his fetlock.

Its not puffy and almost feels like a muscle to touch. Its not warm or causing him any pain. Hes not lame and doesnt seem the slightest bit worried about it, which is why I haven't bothered calling a vet. But I'm a little wary of doing too much with him when I dont know whats causing it.

Anybody have any idea what im talking about?!

 

[Box_Of_Frogs]

Are you absolutely certain that there isn't even a minute, teeny tiny puncture wound to the area? It's adder season or even just a prick from brambles. The trouble is exactly as you have said, if you can't see a tiny speck of blood you wouldn't think to get the vet for antibx. Other than that, I'd watch very closely because minor odd and unexplained things on a horse can very quickly become major odd and unexplained things!