Pip is my 23-year-old dressage horse. We also ride on trails, and occasionally pop over little jumps for fun. About a month ago, I noticed that when I riding Pip at the trot, his back end was not tracking properly with his front end. It was skewed to the left at the walk and trot. It did not seem to bother him. When I was able to observe him from the ground, he was not stepping evenly underneath himself with his back feet. He was standing mainly on the back left foot, as you see in the picture.
The first person I talked with about it was my riding instructor. She did not want to do lessons for fear of hurting him. However when he was turned out in the field with his buddies, he walked, trotted, and finally galloped with them. It seemed pretty clear that he was not in pain.
Next, since the farrier was due at the barn, I had him look at Pip. There was a soft spot on one hoof (a possible bruise) so I suspected he was working on an abscess. However after a few days there was no change. I began a Keratex Hoof Hardener treatment, which seemed to help the soft spot, and he has since been trimmed with no change in his movement.
My favorite chiropractor was tied up and could not see Pip. She looked at the video that I had, and felt the weird tracking was neurological and not chiropractic. A different chiropractor was scheduled to come to the barn, however, so I had her work on Pip. She adjusted several places on Pip’s back end, found no problems at his ribs, and made a small adjustment in him neck. She found a little sensitivity in his left stifle. Pip seemed a bit better (straighter) after the adjustments, but he was not back to normal.
So it was time to see a veterinarian. Pip was not getting better or worse, but I want to be sure he is comfortable, and I want to know what is going on. I put him on a trailer, and hauled him to the vet I have used for years in Apex, “Dr. M.” He is the same vet that helped me through Red’s Sidewinder story. I saw Dr. M on Monday this week. and he did the normal check up. Pip is healthy in all his vitals signs (heart, breathing, etc.). But with hand walking and trotting the vet could see the odd tracking to the left. He pulled Pip’s tail to the sides. In one direction Pip moved easily. In the other direction he would not move. Dr. M also placed Pip’s back feet across each other in both directions. One way, Pip moved his feet immediately back to the normal way they are supposed to be. The other way, though, Pip just left his legs crossed. It was as though he did not know there was something odd.
Dr. M knew what was going through my head. He drew blood for an EPM test. I am in a waiting pattern until the results come back next Monday.
It was interesting talking with him about EPM. He said most horses here in North Carolina have been exposed to EPM, and will have some antibodies in their blood. ( It is like chicken pox in a human. Once you have had it, you will always have some antibodies in your blood. However while you have chicken pox, the antibodies will be off the chart high.) So if Pip has EPM, his bloodwork will show it. EPM is treatable with either Marquis, which is an oral medicine, or with a newer medicine which is a top dressing for his grain. Both are similarly effective in treating it.
It is strange to think I am hoping that Pip has EPM. When my mare Windy had it, she was about four years old. We successfully treated it with Marquis, and I had years of riding with her afterwards. If it is not EPM, I don’t know where we go from here. I’ll keep you posted…
NorthCarolinaHorseFarm 
Thanks for sharing this. My 25 year old appendix quarter horse has this same stance, but on the opposite side. I treated with Marquis thinking it was EPM but saw no improvement. He was injured going over a jump several years ago (before he was in my care) and is now “retired” at my home. My vet called it “sidewinders syndrome” which is usually progressive and fatal, but I’ve had him for 3 years in my care and he has improved slightly (no longer leaning on the stall wall for support) but it’s very hard to trim his right hind, because he seems unable to bear continued weight on the affected left hind. this has resulted in lower leg swelling and hoof problems on his right side because it bears most of his weight, most of the time. I’ll be interested to know how things go for you. My horse was my granddaughters lesson horse for many years and when he became injured and developed this problem, I took him in….he was a great lesson horse and deserves a good retirement. He’s over 16 hh and a registered appendix quarter horse – I don’t know if the Thoroughbred lines have anything to do with this, but I suspect a neurologic injury or progressive neuroligic degeneration. I’ve seen some other signs of neurologic issues now, like quaking in his front legs and twice he has fallen for no reason. (thanks to Barn Cameras I can tell what happened.) he now stays out and is never confined to a stall because of the likelihood of falling on the forehand.
Thank you for this info. It is so hard to find info on Sidewinders syndrome. It seems more and more common as horses live longer. My first exposure to it was my thoroughbred, Red, whose symptoms progressed; he lost weight and muscle tone, and finally lost control. Pip is a Belgian Warmbood with no thoroughbred in his bloodlines.
I think that’s how I found you. I was researching sidewinders and came across your post. So sorry you lost Red. If I recall it was pretty fast deterioration. My horse “Trip” has actually gotten some better . I am just now trying Equi Bone Supplement – just started – I’ll let you know if I see any improvement. I’ts curious that thay have the same stance, just on opposite sides. If you send me a cell phone number I’ll send you some photos of my guy – if that helps in the research dept.