How old is your dog?
Irish Wolfhound youngsters get elbow bursas (hygromas) very frequently, and the general rule is to leave them alone, and they will go away on their own. Unless the bursa is red, hot, or infected looking, do not allow your vet to drain it!!!
If they are drained, they are likely to get infected and cause all manner of problems.
I know they are unsightly, but they will almost always resolve with time. They can be softball sized or even grapefruit sized, truly ugly, but please try to refrain from having it drained. It will just fill up again and might well become infected.
Some people have had good luck with the Dogleg- type padded bandages. They are often caused by the young dog throwing itself down on hard surfaces. You can try to provide padded surfaces and soft beds, but often they prefer to lie on something cool.
My youngsters have had a great many elbow and butt bursas over the years. All have eventually gone away with no treatment.
This is a very common question for new IW owners…I think they need a support group!