No guy wants to even think about anything happening to their 'little man.' But a penis can break. But don't worry, it's much like any other breaking body part--it will heal. That is, it will heal if you get help. Too many men might be embarrased, but would you rather be embarrassed over the fact that during sex you broke your penis, or that during sex later on you can't get hard because you now have erectile dysfunction?
A penis can only 'break' while it is hard. During an erection, blood rushes through the penis. If it is bent or hit quite hard while in this state, the blood can break through one of two 'cylinders' in the penis. If this happens, it will make a loud 'popping' sound, and the penis will quickly turn colors. It will become bruised and red, and likely a large lump will appear. This is the pooling of blood underneath. If the urethra was damaged as well, sometimes the blood may appear at the opening on the head of the penis. Lots of articles and information refer to the broken shape as a 'boomerang' shape.
This typically happens in girl-on-top position or positions from behind (doggie-style). The woman may move in a quick, jerking manner, bending the penis, or the man may pull out to thrust and 'miss' the vagina, hitting either his partner or a close object near them. If this happens, go to the doctor. Even for mild fractures that don't cause much pain. It can cause more pain down the line, erectile dysfunction, or your penis may stay in that slightly-bent shape. This can happen at any age, so please don't hold off going to the doctor!! Yes, there is a short period of time you will have to abstain from sex, but isn't it worth it?
Eric P. , Castle, M.D. "Sexual Health ." Mayo Clinic n. pag. Web. 12 Jul 2011.
Friedman, Emily. "Penile Fractures: More Than a Sex Myth on 'Grey's Anatomy.'." ABC News(Health) 23 January 2009: n. pag. Web. 12 Jul 2011.
Image: "Penile Fracture." NY-Presbyterian Emergency Medicine. Web. 12 Jul 2011.