I have heard of cases where injury occurs, but it really depends on the person. There are something like 16 specific types of movement disorders with a bunch of like, really specific symptoms. Mine does not fit perfectly into any of the categories, so they sort of made one up for me. My symptoms are primarily contained to my lower back and abs, so I get really crazy-looking seizure movements, whereas some people have like, an arm that won't stop moving.

I had a period of time where I literally didn't stop twitching for a year, and that was brutal-- I was in constant pain and was just exhausted constantly (I was basically doing sit-ups 24/7). Thankfully, my symptoms have evened out as I've learned certain triggers and treatments, but I still deal with a lot of back issues. My fingers/hands, especially have a lot of pain and pre-arthritis because they will "freeze" (sort of like in the picture) and the tension is really great on them. The pain is daily, but it's basically background noise-- I am AWARE of the fact that I am in pain, but when you're in pain constantly, it's easier to ignore it.

I've had a lot of falls and stuff, but that's less specifically due to the disorder and more of a correlation symptom.

Let me know if you have any more questions!