Foal with odd swelling on leg

[soloequestrian]

My friend's 5 month old foal has a weird swelling on one hind leg in the fetlock area. It's just above the joint, towards the back where you would find windgalls. It's weird in that it has a very defined shape on both sides of the leg - all windgalls I've come across have been fairly diffuse swelling. Her vet was very dismissive of it, I think just shrugged his shoulders and said to give it time. The swelling is about the size and shape of half a golf ball on either side of the leg, is warm but not particularly more than the other leg and there is no lameness. My friend is a bit worried about it - wondered if anyone had come across anything similar?

 

[Maesfen]

It's possibly the result of a knock while playing and with time will disperse but please keep an eye on it.
I had one that did this and the swellings moved to different limbs (never lame) and finally settled on his hock, stopped there for some time. We decided to take some fluid off to see what we were dealing with and vet was amazed how much there was, three times more than expected. Tests came back that it was the same thing as joint ill (even though 5 months old) so after advice from Rossdales in Newmarket he had a big course of antibiotics (strawberry and banana flavoured but can't remember the name sorry) and he was fine. The swelling never showed again, never been lame and he's just had his 20th birthday!