Question: I have a 14 year-old 14-2hh dressage pony mainly tb. We have had him since last July. Around one month ago while my daughter was having a jumping lesson with him he started hyper-extending his left fore leg, only in the trot and perhaps only 3 times that day, as if he had some rubber from my arena stuck in his boot. That week my daughter rode him 4 times and he increasingly did this extending thing with the left leg and by the end of the week was doing it in walk and trot with both front legs. I called my physio who, although could find a few issues with soreness, nothing that would cause this strange behavior. I called a vet out, checked for lameness and he is sound!, Then we lunged him, with side reins and without, no hyper extension. As soon as I got on him he started doing this thing again both in walk and trot and on both reins and with both front legs. Our Vet put the pony on bute and suggested we keep working him. The next day worked him – he was much worse, tried him on just a headcollar and he still did it. I felt it was conditioned behavior as he only did it twice with the headcollar on. But when I was finished he was breathing really heavy, which was not like him, he is very fit worked by myself 4/5 times a week. I called the vet again and he told me to perhaps rest him. That night had to call vet out on emergency as horse not breathing properly. The vet diagnosed mild pneumonia. Put him on antibiotics for two weeks and Ventapulmin. He had a further week off. Vet checked him and declared him fit to start work. He came back into work yesterday and is still doing the hyper-extension thing, only with front left at the moment. I only rode him for around 10/15 min. Today he has been coughing, no mucous. I have no idea what it could be or where to go from here any suggestions would be welcome.
Answer by April Reeves: I just spend the day speaking with many people/vets/professionals who have lost horses or had unusual symptoms with them. Several ideas came from these conversations.
1. Some virus’s can do very unusual things to horses. We live in a world of super-virus’ that are resistant to our many drugs. The symptoms we are seeing today never existed twenty years ago. Virus’s are difficult to diagnose at times. They need to run their course and antibiotics will not help at all.
2. Thirty years ago you never heard of a horse with cancer, but today the horse next to mine is dying from it, and his last stall friend also passed away last year from tumors in his face. I don’t want to alarm you but your symptoms were very similar to this past horse. He had breathing problems, and extended his back legs when standing, walking and sometimes trotting. One of the tumors in his head put pressure on the part of his brain that controlled motor functions.
3. My take on it is a pinched nerve deep behind the top of the scapula. One of my students horses was throwing her shoulder and leg out forward in a weird way, so we put a thick sheepskin under the saddle and the horse has completely changed her gaits. This mare also had problems with teeth and nose infections, so several days ago we had her head drilled and found an abscess deep within her skull. Hours later she looks happy and is eating! This mare had 2 things wrong with her at the same time, and one diagnosis was not enough to solve her problems.
Perhaps your pony has several things at the same time, confusing it for a single problem. It could be a nerve causing the leg extension and a virus causing the breathing and pneumonia problem.
I have trouble seeing this problem as a training issue or a conditioned response. Horses move erratically because they are uncomfortable, not because they choose to just to mess with humans. Your pony quit doing it when you got off her back.
I never write these things to alarm anyone, but I do tell it the way it is when asked. Often you need another persons POV, which may trigger an idea or something a vet may not have thought of.
As humans experience dramatic changes on earth, our horses are experiencing changes too for the first time. We are doing such damage to our world and I believe we are on the precipice of seeing some very disturbing results of this. While humans are not enduring the changes well, our animals are an obvious and blatant indication that we, as humans, need to make dramatic changes and fast. Twenty years from now we will look back on these times and wonder why we sat idle.
aprilreeveshorsetraining 
nice post