Mallet finger typically occurs with jamming your finger, like hitting a basketball with a straight finger, forcing it to bend when not expected. If the tendon that attaches near the base of your fingernail is unable to withstand this sudden force, it avulses or rips out of the bone creating a droopy fingertip. Unless this tendon is reattached somehow, you will never be able to straighten the tip of your finger again. Typically, this does not interfere with your ability to do things. People seek treatment because they are more concerned about how their finger looks. A small percentage of mallet finger injuries can progress to a swan neck deformity where the tip of your finger is stuck pointing down and the middle knuckle is hyperextended in the opposite direction. This does interfere with finger function and treatment is typically necessary.
Treatment options for mallet finger vary depending on the length of time after injury that the droopy finger shows up (its not always immediate). Treatment is deemed successful if there is little or no extensor tendon lag, meaning you are able to straighten your finger fully.
The most conservative treatment option is long term splinting. This involves wearing a specially made finger brace that holds your finger in a neutral position in hopes that the tendon will reattach via scar tissue. This can be anywhere from six to 14 weeks. Most patients see acceptable success with splinting alone, their finger tip may be not quite straight but less noticeably bent, and do not seek further treatment.
Surgery is the next step if splinting does not work. However, recent review of the literature suggests that despite many different applications of surgical procedures, results are relatively no better than splinting alone.