I've had some do that kind of mess. Farrier came out a couple of weeks ago and we did the colt - well, you would've thought it was his first time of being handled - acted like an idiot. Got tired of messing with him and fighting him, so we twitched him - problem solved.
Think of these young'uns as oh, say 13-year olds! All of a sudden, it's a No, I don't think I will. No, I'm not gonna. They usually see the same reaction from me as my sons would if they told me no - they get a rude awakening!
As far as leading, get you a dressage whip - that work wonders, as you go, tap, if need be, with your left arm. My thing is, if I'm walking, you better be coming. If I turn to face a horse, it's for them to set up, or to stand up and stop immediately. If I walk towards them, it means back your hindend up NOW! (Isn't as harsh as it sounds... HA!)
And if a horse is stupid enough to kick me - well, I kick back. With those little ones, I'm usually lifting them off the ground!
But, yep, mine get stupid every once in a while, too. Last year, right before I broke my arm, and was getting the horses ready, Scamp decided he forgot how to work off the golfcart - now, I ask you... how many months the year before did we do that... I went straight back to the barn, got Kid's stud chain, and oops, all of a sudden he remembered. Yep, thought so.
Sorry about your knee/leg, though... I know that hurts!!!!