I come to the collective hive at my wit’s end.
My 10yo OTTB gelding is back in work after a winter off. I spent all of March lunging him to start getting him back in shape, and started back under saddle in April.
He goes right extremely well. He’s easy to collect, has a nice swinging trot, and picks up the correct lead 99% of the time. Going left, he is more tense and takes a lot longer to warm up. He picks up the correct lead about 60% of the time. My biggest issue is this tranter going left. He ONLY does it if I post on the correct diagonal…he will tranter, pop me off the correct diagonal, and as long as I’m posting to the inside leg (incorrectly), his trot is fine. As soon as I sit for two (or stand, I’ve tried both), he will tranter and pretty much not allow me to post correctly. It’s so frustrating.
My trainer has put 9 rides on him in the last two months. He will start out trantering with her, but she’s able to push him through it, and he gets over it, and it’s stopped by the end of their ride. She rides in spurs, and I don’t - my leg isn’t there yet. She’s also got decades of experience on me, so I’m not sure if this is a training/behavior issue since she’s able to work through it, or if there’s something medical going on. She rode him this past Sunday for about a half hour and he only had minor tranter issues, and once he was totally warmed up, I got on and actually didn’t have any problems. I was SO happy to be able to ride my horse correctly. Last night, it all fell apart again, and I am feeling so defeated.
He does have sticky stifles, but they have greatly improved. He used to lock up and need to move backwards, and now it’s just minor stiffness.
The vet is coming out tomorrow for vaccines, and I’m going to ask her about where to start with diagnostics, but I am hoping that someone can shed some light on this issue. I’m sure I’ll be doing x-rays in the future, but I’m trying not to Google and scare myself haha. Figured this would be a good place to start to get some real-world experience.
He’s very likely lame. Do you have a video of him undersaddle?
Have the vet do a soundness exam, flexions and blocking. Trantering is almost always a sign of physical soreness, and the popping up and being “difficult” when you are on the wrong diagonal would be your biggest clue you are dealing with a physical issue in the horse.
Any time I have had a horse be markedly worse on the off-diagonal, it has been a soft tissue injury in the lower leg… Suspensory, DFFT, etc…
Although now that I think of it, I did have a horse with SI issues that trantered. YMMV.
If he has sticky stifles, chances are, there is something bothering him including the sticky stifles. “Minor stiffness” is still a lameness… and IME, once they have stifle issues that are visibly apparent, that means they were dealing with it for a while, and stifles tend to affect the surrounding apparatus too, meaning they get sore elsewhere… hocks, suspensories, SI… I have not known many sticky stifled horses to have no pain in their stifles.
The other thing about sticky stifles, is they usually get worse after time off, and stifles IME, do very poorly with lunging… You likely are dealing with a general weakness behind, followed by the soreness of the stifles. While he had the winter off, was he outside 24/7 or in a stalled arrangement? What have you done to treat the sticky stifles?
I would have a full work-up with vet tomorrow. Keep us updated. Good luck!
He is always out 24/7 unless the weather is horrible…I try to keep him out and moving as much as possible. He’s on Acti-Flex, and I noticed the most improvement when I put him on STP (like Bute-Less, but a higher potency). Other than that, I just try to keep him in as consistent work as possible. He was only off for the winter due to the death of my previous barn owner and I had to pick up the work at the barn, and then we moved…he also gets chiro adjustments a few times a year, as I can afford them. I am going to have my trainer talk to the vet tomorrow also, and see if we can come up with a POA together. I appreciate your insight 
Get the vet to check him out, seems like he’s going through a physical issue, working him through it isn’t the right way to go about it, as I doubt it’s behavior.
I would get him checked before I keep putting pressure on the issue.
Hope you get this resolved asap!
Beowulf’s advice is excellent. I would also check his back, as the only confirmed tranterer i know currently has a case of kissing spine.
Good luck!
Once you have an answer on the cause if this behavior and start treating it, one thing I would recommend to help you keep an eye on his hind end soundness is to switch diagonals at the trot while maintaining the same direction.
Often if a horse looks “funny” but isn’t obviously lame switching the posting diagonal will make the unsoundness more obvious. There is no correct diagonal. The french school of dressage posts with the inside shoulder. The point of switching is just to keep the horse evenly strong. Your horse is sound when he’s even both ways and on both diagonals.
And, it could simply be a case of not enough Forward.
