I've had broken ribs from being bucked off on three separate occasions. I also broke my foot one winter when I stepped on a frozen horse apple and my foot rolled off of it. The worst injuries I've had were all from big horses as well, and all happened within the last ten years, even though I've had horses and rode all my life.
First one, ten years ago... I had gotten a new horse and was saddle training it. He was doing very well in the round pen. It was late May and I bathed him and put Show Sheen on him to show off his beautiful blood-bay coloring as we were having company. For some stupid reason, before the company arrived, I decided to get on him bareback and ride him down a trail. He saw a rabbit and spooked. I fell to the ground, because the danged Show Sheen was so slippery! The horse reared and came down on my upper arm. The pain was incredible! Went to the ER and found his hoof print on my upper arm! He'd also pulled the bicep muscle completely off the bone. I had several surgeries to repin it to the bone, but so many lymph nodes were also crushed that it was a year of physical therapy, in which they had to do some weird stimulation of all the major lymph nodes in my body. It was over a year before I could use that arm without terrible pain, and it's never been the same.
Then, about 7 years ago, I was riding the same horse and we were in a sandy area, and suddenly I could feel the horse starting to go down, as if he were going to go down and roll in the sand! I tried pulling him up but couldn't, so i tried to jump out of the saddle, and *almost* made it. Not quite, though. My one foot was still caught in the stirrup and when the horse went down he twisted my leg under him, tearing the ACL and popping my knee cap. Back to surgery again.
Then, just over three years ago, the SAME D@MNED HORSE.... we were riding on our trails, with my husband and a friend riding behind us. My horse was always such a fast walker, and the others were lagging far behind. So, we were going down a very slight hill and I pulled my horse up to wait for the others. He stood there for maybe two minutes, and then suddenly out of the blue, he gave a totally unexpected wild buck, which threw me out of the saddle and into a tree. I broke my collar bone and completely tore my rotator cuff in half. Another surgery and five months of recuperation.
I still love that horse like crazy, but I just don't ride him any more, LOL! He's got incredible ground manners and is so pretty!