I ignore my neds, as I have been told that anything that is tight enough to disperse the fluid isn't going to be much good for the joint itself.
Cold hosing can help.
Used to ride a horse with them, and we used to ignore them. They went down with exercise but if he was standing around they wouldfill up again. After comps we put that special clay on and hosed. His owner put magnetic boots on aswell which did seem to really help. I wouldnt worry about them too much (apart from when they are forming).
they're usually cosmetic blemishes. if needed, stable bandages overnight will reduce them the night before a show. some people swear by magnetic boots. mostly you should just leave them alone.
Any horse whether ridden or turned out may get them. You need to just check to see if they increase in size or other related areas are swelling, otherwise hosing and leaving are the only real options. For a unfit horse, trotting too fast/hard on the road can cause them. They are concusions, little sacks of fluid and there to prevent harm to other bits and pieces to put it in laymans terms.
Dont worry, just be aware of them, it does not affect soundness.