My baby didn't fall down the steps but my hubby did! He was carrying her down to bed and slipped on one of her toys on the steps. He went sliding/tumbling all the way to the bottom but was able to safely put her down as he began to fall. The sound was terrible and my first thought was not if hubby was ok, but whether he had fallen on Maggie!
He was sore for a while, but I don't think anything hurt for long.
Moral? Always make sure the toys are off the steps!
I hope your baby feels better soon. I dread the day my girl should needs surgery because she is a bundle of running and jumping up and down from furniture. I don't know how we would handle the restrictions. I'm afraid her activity will lead to bad knees. Luckily she is 9.5 pounds, so I think she is big enough for jumping on and off sofa safely.
At least your baby is young enough that the habits of jumping on and off furniture are probably not as set, and you should be able to train her to stay down. Good luck and I hope she feels better soon!