Ben Williamson wrote:

Anyway, if you've ever been elbow blocked (thai kickbox style for
example) right above the foot, you know what I'm talking about... it hurts
like hell.  I'm also not sure about the stance in the fanfic, but if the
defending martial artist were good enough, they could not only lower the
stance to strengthen it, but also reposition their leg such that the
sweepers's extended limb struck at a weak point(of the attacker).  In
short... given factors such as Ranma's youth and lack of understanding of
his female form, and even a little bad luck thrown in for poetic license,
this is by no means unrealistic.

Sorry for gibbering... but martial arts is my main hobby.  Hertza Haeon!

In that case he would not break the bone as was suggested but would be
damaging the joint. which is the jist of what I was telling him.