wow, that kid gets rocked lol. One punch knock out, and he may of broke or messed up his foot too. He was knocked out cold and his weight may have messed his foot up too heh.
Nothing is wrong with his foot. He just got knocked out and his leg had a spasm from the resulting blow. The impact sent the pain all along his nervous system resulting in the leg being locked up and the foot twitching.
Some say that his heart ticks like a watch, and that he’s confused by stairs... All we know is he's called The Stig.