Our son has been watching too much TV. In a mock kung-fu move, he kicked his leg out and then punched a two-by-four intending to break it in half. All he accomplished was breaking the knuckle of his little finger. Right now, when he makes a fist, that finger is flat where the knuckle should be. Will this pop back out and heal?
You have described the Boxer’s knuckle perfectly. Most people with this injury also report painful swelling as well. Treatment is usually by splinting the affected finger together. A special gutter splint is used to hold the fingers in a position of partial flexion.

X-rays are taken two weeks after the injury to check the position of the bones and joints. If the placement is worse instead of better, then adjustments must be made to the splint position. The fingers are held still for four to six weeks to encourage healing.

After this period of immobilization, six weeks of hand therapy in an aggressive rehab program is advised. Flexibility and strength are eventually restored but the knuckle may not ever return to its original appearance.