Hygromas are thought to be the body's reaction to repeated trauma to an area in which bone lines close to the surface of the skin. Usually they occur on elbows. They are a collection of serum in a thick capsule that the body builds to cushion the area. Affected dogs are not usually lame. If these are small, just providing padding over the area can allow them to either maintain their present size or even shrink. However, since they can get to be pretty large and will occasionally get infected, it is not uncommon for veterinarians to recommend surgical drainage, usually with post-operative bandaging to protect the area. If they get really large and then infected, it can be necessary to do skin grafting to fix the defect made in removing the hygroma.