A broken leg (leg fracture) will be severely painful and may be swollen or bruised. You usually won't be able to walk on it. If it's a severe fracture, the leg may be an odd shape and the bone may even be poking out of the skin.
Disclaimer: The information provided here should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. The information is provided solely for educational purpose and should not be considered a substitute for medical advice.