Rocky Marchiano used to pummel the crap out of his opponent's arms in the first few rounds, until they couldn't maintain a tight guard, then he'd go to work on them.
That's about as realistic a real world sport fighting scenario as I can think of.
Police are taught to target the arms and leg muscles and not the joints with their nightsticks and pr24's. Probably more for preventing permanent injury to the joints and liability though. Most cops I've trained with the stick found that what they were taught on the force was useless against a larger, or drugged out, or adrenaline crazed attacker.
Let's also take into consideration that there are what we call, non-responders. Anyone doing point striking or chin-na has come into contact with these people. Sure, they won't feel the pain, until it's too late and the joint is broken.
"My Gung-Fu may not be Your Gung-Fu.
Gwok-Si, Gwok-Faht"
"I will not be part of the generation
that killed Kung-Fu."
....step.