Although at this point my shoulders are “almost” normal, I’ll add my story.
Back in late 1999, before I started riding again, my shoulder joints started “freezing.” I gradually lost range of motion until I couldn’t raise my hands above elbow level (I was teaching at the time, and it was back in the blackboard days, so this was a problem.) I have Type 1 diabetes, which makes me more prone to stuff like this. I did a round of PT, but continued to get worse, and finally ended up having surgery on both shoulders at the same time.
“Frozen shoulder” is a condition where the joint develops adhesions, so the surgery (simple version) is to put you under, yank your shoulder around to break up the adhesions, and get you into PT that same day, because the adhesions can re-form very quickly. For the right shoulder, that’s what the surgeon did, but for the left he had to go in with a scope and break up the adhesions. I was in PT 5 hours after surgery and continued with PT 3-5 times a week for 8 weeks (at which point I joined a gym, because my insurer wouldn’t pay for more PT.) I went from about 50% ROM before surgery to 90% in the left and 95% in the right. It’s been 13 years and my shoulders still get a bit cranky, especially in cold weather. But riding really helps.
In 2006 I started riding again, and in 2008 had a riding accident that trashed my left collarbone (I also broke 5 ribs on the left side, and partially collapsed my lung. Fainted while riding at a hand-gallopy pace between jumps, slipped right off and landed on the point of my left shoulder.) So my left shoulder is collapsed in, and the hardware holding the collarbone together means I can’t “uncollapse” it. I can’t turn my torso to the right as much as to the left, so I am an “asymmetrical” rider. Luckily I can still ride; it would be a problem if I was trying to ride at the upper levels, but since I’m really just your average middle aged adult re-rider, it’s more of a frustration.
But yeah, this isn’t fun stuff.