You are right to be nervous!
A few years ago, my fiance at the time and I had a kitten and when we came home from being gone all day at Thanksgiving with the family we couldn't find the kitten... we finally found her wedged behind a bookcase she had fallen behind.
She was not herself and just wanted to lay in bed (not normal for our very hyper kitten). We took her to the vet and found she had dislocated and cracked her hip!
She had surgery where they removed the hip ball and repositioned her hip between two muscles. It was TERRIBLE. Poor kitten looked like frankenstein. She recovered great although she always ran and hopped a little different than before, but I still feel terrible thinking about it.