Why don't professional athletes use local anesthesia instead of cortisone during games?

Potentially bad: Pain is the body's way of telling you there is something wrong. If you numb it up with a local anesthetic, and you mask the signals coming from that region, you can hurt it worse. Steroids are anti-inflammatory agents that reduce swelling and inflammation but don't mask the issues. This way you treat the underlying condition and allow more function.

Numbness: The numbess of local anesthesia not only reduces pain, it also reduces feedback, control and strength of your limbs. Think of how your mouth works after being numbed for dental work. Now imagine trying to throw a ball with a numb, heavy arm. You won't feel shoulder pain, but you also won't be able to perform athletic skills.

Effects: Local anesthetics not only numb the site of injury, but they can also cause motor weakness. This effect would not make it a good choice for athletes.