Hoof and lameness help (picture included)

[doubletrouble25]

Looking for advice for my horse that I am currently free leasing. He is a 15 year old appendix QH that I have been leasing for approximately 6 months. Several months ago I noticed he was off in the RF, no heat, no swelling, had the vet out to do xrays and a nerve block- ended up that he had mild coffin joint arthritis in his RF with no navicular involvement. I had his coffin joint injected at the end of March and he has been sound ever since.. Until Thursday. Additional background: his RF also happens to be clubbed which wasn't managed too well by his previous owner's farrier who tried to make it look like his other 3 hooves. When we got films, it showed that our farrier was getting good angles. Last Monday I went down to ride him and took him over some xrails and did some small course work with him and he was phenominal, Tuesday I didn't ride, Wednesday I went down and he was holding a lot of tension but didn't feel lame at all, just felt like he was having an off day.. Thursday I went down and he was slightly lame to the left (new for him) and noticeably lame to the right. We figured because of his clubbed RF and him being due for a trim and shoes the following week, that maybe he was just sensitive. Saturday the farrier came out and trimmed and shod him. SUnday I was out of town, and Monday I went out and lunged him and he was barely barely barely off to the L, but off to the R, just not quite as bad. I inspected him all around and no heat or swelling anywhere, but I did find a horizontal crack with a tiny hole to his back R hoof, which I assumed would be an abscess that had burst, it's up near the coronary band. However, no heat, no swelling, no drainage from that hole. It looks like it could be old but I don't know how I would have missed it, how the farrier would have missed it, or how he wouldn't have been lame until just now... wouldn't he have been lame before the abscess popped, not after? Anyway, I hosed him off really good and sent a picture to my barn owner who thought it looked like just a superficial crack that wasn't a big deal. To me it still looks like a burst abscess but I don't have a lot of experience. And now I'm like.. what do I do? I think I may go down tomorrow to soak it, walk him, and wrap it. Do I do this for a few days, check for improvement and then call the vet? Would this really cause lameness? Or, is it more likely that the lameness is related to his arthritis in his coffin joint on the RF? If this is the case, I am going to have to make a terribly hard decision as to whether or not I should keep my boy, or give him back to his owner. If he was my horse, I would do everything.. but he's 15, he's not technically mine, and the end result may end up being that I can't use him for my discipline.. which if he was mine, I would absolutely keep him regardless, but being that he's not.. I don't know. I will have to think about everything.

I guess I'm wondering what your opinions are. Below I have a picture of his right hind. It's so hard to tell whether he is off in the right hind or right front, but he is definitely off to the right. Do you think this is an abscess that popped? And if so, do you think this could be causing his lameness? And how should I treat it now that it has popped? As I said, I have not seen any drainage or anything.. should I do epsom soaks and poultice wraps or..? I plan on talking to my barn owner in person tomorrow and showing her in person and then calling the vet/farrier. Of course farrier is on holiday this week..

ETA: I just feel like it's weird if this WAS an abscess, that he wasn't lame prior to the crack, but now that the abscess popped, he is lame? Shouldn't that be opposite? Leads me to feel like it could just be his arthritis in which case.. I have bad feelings about all of this :/

Sorry for the long story for my first post! I am just overthinking everything and need advice.

 

[Exploding Chestnuts]

I am not sure how to answer, if I had so many questions, I might pop a wet poultice on and see if there is any fluid, I know this is unlikely though.
Check for heat and maybe try a bit of manipulation to find any pain source.

 

[Meowy Catkin]

That does look like it could be an old abscess hole. You can see that it's grown down a bit, as it would have originally been at the top of the coronet band right where the fur starts. Normally, once they've popped, the horse comes sound and they grow out with no further bother.

 

[amandap]

I think the majority of abscesses go un noticed especially in hind hooves. As the split is growing down I think the abscess is most likely done so forget about it, unless poulticing makes you feel better. The split will grow down and out over time.

Don't know what to say about the other lameness I'm afraid but I don't think that abscess is a current problem.