On my horses back leg he has a slight lump, it is not fluidy at all, and down the front of his cannon bone, slightly to the side. It is not bothering him to touch it he is 100% sound and there is no mark where he could have been bitten. It just feels like the bone but sticking out more if that makes sense!! I cold hosed it a bit today and he held his leg up, but is funny about the hose anyway so not sure if this was a reaction to the lump or the hose!
As you know my pony quite well, you'll know that she has had everything under the sun in her legs! Signs of a splint forming are heat, varying stiffness and sometimes lameness and yes, that hard lump just to the inside of the cannon bone. Once they are formed, they don't cause trouble (well, they haven't caused us any trouble yet!) However, I was told to ease up on the work a little. We had a horse have quite a bad one form recently on the yard and she was lame for a few days, with heat and swelling. We gave her 10 minutes of cold hosing twice a day, and whacked on witch hazel and arnica gel.