Hi again. Since the vet ruled out hemotoma, and it was from inside the stall---I have also seen when a horse is rolling, he gets stuck in a corner or puts his leg thru a board and then twists his shoulder severely while trying to get up. Did the vet take a xray? On a shoulder there is no where for the fluid from swelling to go othere than above the bone and this causes a pool of fluid like this. Still hose it regurely, limit excercise--only leading him if you do and usually Bute is good for pain and inflamation. There is a mixture I have the vet make up for pulls and strains where swelling starts, and that is: Cortosone and DMSO combined. Apply it once a day. See if you can get that.