A finger that bends down at the end joint and cannot be straightened is called a mallet finger. It is caused by an injury to the tendon that straightens the finger. A splint worn day and night for 6-8 weeks will cure the problem in most cases.
A mallet finger is where the end of a finger is bent (flexed) towards the palm and cannot straighten.
The usual cause is an injury to the end of the finger. The injury tears the the tendon that straightens (extends) the end of the finger.
It is sometimes called baseball finger as it is a common injury when trying to catch a fast, hard ball. If the catch is missed slightly then the ball hits the straight finger. This may force the end of the finger to bend (flex) further than normal and tear the tendon. Without the use of this tendon, the finger stays bent (flexed).
Sports injuries are the common cause of mallet finger, but any injury that forces the end joint of a finger to over-bend can cause it. (Sometimes the tendon does not tear but the injury causes a piece of bone to be pulled off the finger where the tendon is attached. The result is the same, as the tendon then cannot pull on the bone.)
After the injury, the end of your finger may become painful and swollen. The end of that finger will lie in a bent position and you will not be able to straighten it at the end.
A splint is worn for 6-8 weeks to keep the finger straight with the end joint bent backwards slightly (overextended). It must be worn all the time, day and night. There are many different types of splints available. The type of splint given often depends on the size and shape of your finger.
You must not take the splint off at any time during this treatment! If you do need to take it off (for example to wash) then you must keep that finger straight and not allow it to bend. This allows the two ends of the torn tendon or bone to stay together and heal. About 3 in 4 cases heal well with this treatment.
Surgery is needed to repair the torn tendon if the above fails. (Surgery may be advised straight away if there is an open wound, but most injuries that cause mallet finger do not cut the skin.)
It may take several months for your finger to regain function properly at the end. Any redness, swelling and tenderness of your skin over the end of your finger may persist for the first few months after the injury. These symptoms will usually improve eventually.