I think the point you've missed is that a helmet is a magical device that projects a protective aura all around the cyclist, so if you had fallen off and broken your knee it was probably because you didn't have a helmet on. If you'd been wearing one, your knee would have been fine.
I believe they work using a combination of tiny crystals and magnets although I admit I am not completely up on all the sciency bits.
I think the point you've missed is that a helmet is a magical device that projects a protective aura all around the cyclist, so if you had fallen off and broken your knee it was probably because you didn't have a helmet on. If you'd been wearing one, your knee would have been fine.
I believe they work using a combination of tiny crystals and magnets although I admit I am not completely up on all the sciency bits.