So, I was watching this weekend's nightmare - I mean Packer game - and in jumping up and down all night, apparently repeatedly banged my calf against the wooden chair seat. At the time it was happening, I didn't notice it, so I wasn't banging it very hard. Later is started to hurt, so I moved seats. Later Sunday night I discovered a massive bruise on my leg (like 4 inches square!). Is this normal? It seems like an extreme bruise for not being hit by a baseball bat or something. What could cause this?