Do curveballs hurt your arm

Answer 1

Yes, it does place some pressure on the tendons, however, when you supinate (turn arm clockwise if right handed) your radius and humerus ram together and rub together. If you are not old enough, you can also seriously damage your growth plates.

Answer 2

No, it does not, if you throw it correctly. Many pitchers who throw the knuckleball have pitched late into their 40's and been successful, Hoyt Wilhelm and Phil Neikro come to mind.

Actually, some pitchers have been forced to throw the knuckleball to survive in Baseball after suffering some arm injury.

One such pitcher is Major Leaguer R. A. Dickey.

Answer 3

It depends on what type you are throwing. I'm 11 and I throw a 12-6 curveball. you put your index finger at the top and put your thumb at the bottom. Throw this like a fastball (Don't flick your wrist). This will make it curve a lot without hurting your arm.