Tennis elbow may be caused by:

• A poor backhand technique in tennis.
• A racket grip that is too small.
• Strings that are too tight.
• Playing with wet, heavy balls.
• Repetitive activities such as using a screwdriver, painting or typing.

Two types of onset are commonly seen:
Sudden Onset: Sudden onset of tennis elbow occurs in a single instance of exertion such as a late back hand where the extensors of the wrist become strained. This is thought to correspond to micro-tearing of the tendon.
Late Onset: This normally takes place within 24-72 hours after an intensive term of unaccustomed wrist extension. Examples may be a tennis player using a new racket or even a person who's spent a weekend doing DIY.