So just as a pre-cursor, she's already been to the vet to be x-ray'd, and she goes back tomorrow for ultra sounds. 

I've got a filly who randomly presented with a swollen hock. I had to take a mare for an ultrasound anyways so she went with me to the vet the very same day we noticed it. First thing they thought was OCD, but their x-ray machine was broken, so we went back 3 days later once they got it back up and running. She flexed sound, has no indication of being even slightly off. Her x-rays are 100% clean. We x-ray'd both hock and stifles just to have them on record and have a comparison. 

They said maybe she just slipped while turned out. 2 weeks barn rest and see where she's at. So it's been 2 weeks, and while the swelling has decreased a bit, it's definitely not back to normal yet. I didn't bother taking photos yesterday since she goes back in tomorrow. 

My question is, has anyone ever had any experience with something like this? What you did to help the healing along? Maybe what I should brace myself for? 

Pics are of the day I pulled her in and noticed the swelling. 

I'd guess she has a hemotoma in there (basically bruising and swelling from impact) Ultrasound will tell you more. 

I will be absolutely thrilled if that's all it is! I FINALLY found my Hidez Ice Socks that were stuffed into a corner of the tack room, so I've been doing that for the last few days and it seems to be helping a little. 

I would want to tap the joint fluid, check the white cell count and look for fibrin. Something is causing that fluid buildup. My suspicion would be that she has somehow damaged some cartilage in one of the joints, which may or may not show up in an ultrasound.

I’ve seen torn medial collaterals cause that type of effusion. Your vet should be able to check he collateral ligaments in the hock Area when he does the ultrasound.

I'll have to write that down and ask him. Thanks so much! 

Keep us posted please

Vet here, can you share the x-rays? If there are no radiographic changes a collateral ligament injury would be high on my list. 

I'll ask if they can be sent to me this afternoon when I get there! 

IF a collateral ligament injury is the case, what would her prognosis look like? Obviously I know there will be some variation based on the severity; just hoping for a ballpark "she could be sound to ride" or "I wouldn't get my hopes up on a performance career" lol 

Collateral lig is usually easier to heal up than a suspensory but it’s the same treatment: stall rest , PRP, laser , regular ultrasounds to measure healing.

Update after our 2nd appointment yesterday. This appointment was with their leg specialist. 

1st thing upon arival was to trot and see how she was moving. Flexed and trotted again. Still completely sound with no indication of being sore. 

His first thing was to tell me that he often has people ask him to inject these types of thing, but that he doesn't inject horses her age as it just masks the issue. I told him I'd really rather not inject her "just because", so no issue there. Thank goodness that we were on the same page with that one. lol He then suggested more x-rays to see if something had maybe shifted in her hock or if something just might have flat been missed prior. I'm game for anything at this point so we re x-ray'd and found that she is still 100% clean with no structural changes/imperfections. I then asked about ultrasounds. He said that given she is not even remotely sore, his suspicions of this being a ligament issue were low. I requested them anyways. It's just money, right? And of course, her ultrasound was clean as well. (side note: I'm so proud of how well this filly has handled all the hauling, exams, exam rooms, x-rays, cold sticky ultrasound gel, etc. She's been cool as a cucumber for all of it. The staff here know her sire and dam extremely well, and they give her daddy FULL credit for passing on his temperment )

So the conclusion is basically that she sprained it. She got a compression wrap and anti-inflammatories with 30 more days of stall rest. We're going to continue with the compression ice socks for 10 more days, along with a BOT hock wrap in the evenings for 3 more weeks. I'm pretty relieved to know she's not going to be nothing more than a broodmare at 2 years old. Plus I guess we've got currect x-rays of hocks and stifles should we need to compare at any point in the future!