Mcl tear but no pain?

I have torn my mcl, May be acl but i know for a fact one of them is torn.. But why is there only pain when i bend it or straighten it all the way?? Like i heard the pop and all that.. had the mri and its torn but why doesnt it hurt? I still feel unstable when i try and walk on it and it buckles and all that stuff i just wanna know why it doesnt hurt except to bend it or straighten it.. Thanks :)