Here's the thing - she's not limping, she's out in the pasture running, jumping,and kicking up her heels, I can poke and prod at this thing and there's no pain response from her at all, it's not hot and there's no heat or swelling in any other tissue. I checked her hooves and she's good. She also has this mannerism that she does when she eats (always has, since she was a baby) where when she eats her grain she has to stand on 3 legs. She just picks up her left front and stands there with it tucked up against her and her head in her bucket (she's not pawing or impatient or anything...just standing there like a flamingo). This lumpy thing is on her right front, so she actually stands there and puts a lot of weight on the leg with the lump and has no trouble and shows no signs, whatsoever, that this thing is bothering her.
Any ideas on what it could be?