A penis fracture
A penis can’t actually break because it’s not a bone. However, if a large object falls on a penis while it is erect, or it is bent rapidly in one direction, the blood vessels can break. And this is extremely painful.
What to do
This one is pretty serious. If this happens to your partner, go to the emergency room immediately. Your doctor will most likely have to perform surgery. If a penis fracture is not treated right away, the man can lose his ability to have future erections.