Every year when the baseball season gets underway, doctors start seeing cases of "baseball finger." This condition, which is also called "mallet finger," is often caused when a ball hits the tip of your finger, bending it down.
Fingers can bend down (toward the palm of your hand) only about 35 to 40 degrees. The force of a batted ball can push the finger beyond that limit and tear the tendon that controls muscle movement in the finger. (Full story)