Crippled? ( Spoiler!!! )

This was a pretty good B picture but I've got a little problem with the ending. Eric's nephew Carl hobbles around the entire movie on a cane, apparently badly crippled. Then, at the very end of the movie he get's into a terrific, knock down, drag out fist fight with Eric, even gets shoved down the stairs! But he still manages to beat the tar out of Eric and push him out onto the faulty balcony. What gives?