We are, after all, dealing with someone who thinks that pain is forever so it's not hard to see that her belief that falling on her rump means that she'll be crippled for life and thus be sent away to an assisted living home for being useless to herself and everyone else is really why she fears sports. Her tendency to wring her hands and moan piteously about how evil, conflict-causing MEN want to ruin a good time by worrying about who wins is a smoke-screen meant to disguise her fear that playing hockey will inevitably lead to Michael ending up as a hopeless cripple she'll be stuck taking care of.
Well, there's that and her default hatred of any scenario in which the child DARES to set the agenda at his poooooooooooooor mother's expense. It isn't about having fun or winning trophies or making friends, it's about being a wicked, selfish, ungrateful brat dictating to an adult in defiance of all that is good and true and pure. Heh. If Mike did manage to end up with a steel plate in his head, Elly would think that he did it on purpose to mess up her life because he hates her.