What compels people to share all the gory details of injuries/surguries?

Two different times today I witnessed two different people sharing all the gory intimate details of their surgery or injury. One girl went on for a good five minutes (while I was waiting for an elevator) about all the things that were done to her knee during a recent surgery. It was graphic and gross and way too much information. During a class today, a guy who was using crutches gave every minute detail about how he came to need them, how awful it was, and how much it still hurt him. Why do some people feel the need to share in such detail?