You can injure the UCL if you stress it over and over again. This is called an “overuse” injury. Repeated overhand throwing can weaken, stretch and irritate the ligament. It can partially or completely tear the ligament, or cause one end to pull away from the bone.
A UCL injury causes pain on the inner side of the elbow. Your elbow may feel weak and unstable, and you may not be able to throw as fast as you like. If you tear the UCL, you may feel a pop when it happens. This is painful. It prevents you from throwing. You may also have a tingling or numbness in the last two fingers of your hand.
Treatment depends on how badly you’ve injured the ligament. You may benefit from rest, medications and injections. Physical therapy may help. A complete tear can be fixed with surgery.