I kind of had a problem with this. I was attempt to get my mare to lope (the previous owner said she used to, but didn't like to anymore. I chalked it up to being out of shape, but have discovered it to be her hip so chiro time!) ANYWAY, she was being a butt and my BO, who does endurance racing, asked if I wanted to go on a 10 mile conditioning workout with her and their trainer.
I said yes and used one of their saddles because mine was actually meant for a kid. I'm skinny, but taller, so the stirrups make me look like a jockey. I'm selling it now.
And 2 years ago I had torn my MCL in my right knee (completely unhorse related), but it was misdiagnosed for a year and a half, so I never got the surgery I needed and had/still somewhat have a limp because of the way I learned to carry my hip. Now when I post, I naturally put more weight on my left leg or my right knee will twist out of place (a brace doesn't help enough).
5 miles in, I rolled my left ankle in the stirrup. I was okay and asked to walk for while. When we started again, I rolled it again. I tried putting the majority of my weight on my right leg, but inturn, messed up my knee. It got to the point where I couldn't stand.
This was all with a horse I had never ridden or even met before.
The point of this rant was that he had an odd trot that wasn't smooth and I had a ridiculous time trying to get the right rhythm. I've been told I post like an English rider. Especially because of an accident last year where I work as a wrangler, we have to now wear helmets. I looked very English. (Nothing against them, of course, but we all ride Western.)