Left Leg hard to straighten and is very uncomfortable?!

This night I was just walking normally until then my left leg feels weird. It's like pain when I straighten it, and seems it can't be cracked (crack your knuckles, sort of thing). It hurts the most when I try and straighten and stretch it, and hurts the least when I bend my knee. It hurts on the left side of my left leg, and I got a feeling it must need to be cracked or something. But when I try and straighten it, it hurts.

At first I got some cramps, then this happened...

(Jumping to conclusions: I hope my left leg is not broken)

What is it, what caused it, and how to stop it?



It doesn't really hurt when I fold my left leg.