I wanted to add a few thoughts. I own a horse with a long back and a history of stifle issues. I was always advised NOT to longe him because "circles are bad" for stifles. This year I added longeing to his exercise program and his is better than ever, more even behind and stronger and sounder than he's ever been (schooling 2nd, playing with 3rd).
If you aren't already doing so, try adding two sessions per week longeing over trotting poles, with side reins so he's working round and over his back. I also work mine a little bit in shoulder-in at the walk on the longe in between trot sessions, no more than 20-25 minute sessions altogether. I don't do the poles the entire time but make sure he does even repetitions both directions. Sometimes a short session will be his warm-up and then I get on and ride (easy warm-up for me).
If you do this consistently, I would be surprised if you don't see a more even horse in 30 days or so.
He sure can - looks rather nice Have you ever done belly lifts with him? If so, what did you get. Nice abdominal work releasing the topline or an angry look and dancing sideways?
My attempts at belly lifts are abysmal for some reason. I keep on trying to get them done and do them properly but get no results. He has had them done though, and no reaction. He lifts up really well.
So I had a vet out today for the last time; the best lameness vet that I could find.
Stifles looked really strong. Hocks showed nothing. Flexions were 100%. No pain in the back or by the SI. Backing up shows no abnormality, and his patella appears to be quite solid and strong. No indication of anything neurological. Blood has been pulled as a "just in case" type of thing, but vet doesn't think anything will pop up. So that didn't leave us with much.
Nothing absolutely one hundred percent definitive, but his best guess was a really mild case of something similar to stringhalt brought on by muscular abnormilities. The positive news is that when he watched me ride the horse undersaddle, he said that if I made the inside hind left really stretch forward underneath himself, you could see nothing at all, but more importantly, he was able to actually stretch that leg out. He's also completely symmetrical in his movement, so it apparently hasn't affected his muscles that much. At most, the vet said he saw it at the canter 2-3 times, with 5-6 laps around the arena while I was riding him. He believes that these representations of stringhalt are generally muscular, perhaps from a trauma in which the muscles healed funny, and while it might always be there at some point while he's being lunged or ridden, he says that it shouldn't really impact his riding career all that much. He's being schooling some 2nd level movements with my trainer now and seems to be holding up to getting more of a collected canter, so we'll have to see how it goes with him.
The goal right now is to try to really build up that side and get him really reaching with that hind left; so lots of circles, shoulder ins, ect. The vet also gave me the number of an apparently really good horse masseuse which might be able to pinpoint something. He said there was a chance that it might be able to resolve itself eventually as he strengthens more and more and is forced to extend and stretch that leg out. I hope so.
But, the good news is that I'm comfortable letting it go, despite the fact that it wasn't a 100% definitive answer. I've done everything possible to try to figure it out; it doesn't appear to make him uncomfortable or really affect him all that much undersaddle, so I'll let him be and hopefully just enjoy him.
In my opinion, a horse is the animal to have. 1300 pounds of raw muscle, power, grace, and sweat between your legs - it's something you just can't get from a pet hamster.