I have a wonderful horse who at ages 3 and 4 was the most tractable and easy animal on the planet. Then he turned 5 and was a raging lunatic for a year. At 6 was a baby green horse. At 7 he was a horse.
Once a year, usually in august, he would explode in a bucking fit out of nowhere and dump every rider who rode him for a week or so. Flatting, jumping, you name it. That week, everyone ate dirt. Violent fits. And then they were over like they never happened.
This happened from age 3-11. And then at 11 he suddenly started stopping at jumps which was new for him. He had a full work up and that’s when we discovered the kissing spine and the accompanying soft tissue injuries in both front feet.
This horse was so stoic and kind, he would literally go until he couldn’t and then explode. He showed all summer and by the end of august it was more than he could take.
I tell this story to say a couple things—- if you suspect it’s physical, get it checked. What’s the harm? If the vet check is clean that’s a helpful data point. I don’t think even green babies explode, truly explode, out of just freshness. Exploding and carrying on is more energy than working and a sign of resistance that often reflects some physical pain. A little play is not the same as a full on hard bucking spree.
If it comes out of nowhere and doesn’t seem to be prompted by inexperience, suspect a physical component. A horse that is fresh after seeing something for the first time, that seems green to me. A horse that has done the thing several times and then suddenly has a significant reaction to doing the same thing seems more physical to me.
And, check the feet and back. These are places where pain doesn’t always show as “lameness.” Especially bilateral foot pain can be hard to spot.
FWIW my horse had the happiest of endings. I did the ligament snipping surgery, rested him, restarted him slow, and he’s better than ever and has been going for years since then. He does an easier job now than he used to but he’s also older and he’s packing my sorry ass around (for which he deserves a medal) and I don’t care to jump the height he used to. But he’s totally sound and happy and useful. I wish I had picked up on what he was trying to tell me sooner 