Conformation
A problem with their hocks or stifles
Not working properly
Quite a few things really-just mentioned a few. My previous horse does it-she never had a problem soundness wise- just her poor conformation, in fact although she drags behons you cannot tell from riding her-apart from hearing her feet scrape on the tarmac on hacks. New owners had it breifly investigated and was given the all clear as far as i know to any problems.
Patches is 8 and has always, in the four years Just _Nigel owned her, dragged her feet. She passed a five stage vetting and I've owned her for 17 months now (wow that long!)
I had it looked at briefly by the vets and have been told that what she displays is typical for a horse with Bone spavins. However, her history doesn't suggest this as she's always done the same since a young horse (indeed she drags far less now than she did). Rarely does she drag in walk now on the roads but will sometimes drag, or as I prefer to describe it she taps her back feet back down during the stride, in trot. Conformationally her back legs look very long and she isn't overly well muscled in the second thigh area. Upon flexion she doesn't move any differently than she does before flexion. If you saw her you'd perhaps think she looked lame, but the vet assures me it's her gait and not a mechanical lameness.
She backs up well under saddle and in-hand and can cross her feet over when turning in a very tight circle. This rules out shivers and stringhalt. There is no sign of any sacroiliac joint/ligament damage which would also be a cause for some horse's dragging their toes.
My vet suspects she has a sort of delayed release of the patella locking mechanism which means that she doesn't suffer upward fixation of the patella, just a jerk as the leg is stretched out behind during the stride which means she snatches the foot and it taps back down on the floor.
However, I have also been warned by the vet to not rule out that at some point in the future she could end up with spavins as she is the type of horse, conformationally, that would suffer. Huge hocks.
It's common in young horses and certain heavier breeds. Patches moves very much like a couple of Clydesdales I saw at a show this summer, perhaps that's in her genetic make up...I have no idea of her breeding.
All of above and Can be a sign of wobblers but only if it is the dragging feet combined with general inco-ordination (unable to back up, unable to cross back legs over properly on a turn about the haunches, etc etc etc)
My old horse used to drag his toes in trot - this was due to a weak pelvis. There was nothing we could do and he used to get through the toes of his shoes within 4 weeks - expensive habit
Dragging back feet can be due to a horse not being fit I think. When I first brought my pony back into work after a few years rest he toe tapped a little at the back. After lots of fittening work he hardly does it now. I also agree with Patches response regarding toe tapping as he too is very long in his hind legs and I put this down as the reason. Hes also 20 years old now so that may have something to do with it! Although hes never worn his shoes down so doesnt do it badly.
My horse drags his hind toes in the school, never noticed it out on a hack. The sand wears his toes away slightly. He is a lazy boy and the school can ride deep so Ive never really give it much thought. Maybe I should keep an eye on it.