Extensor Tendon Subluxation / Boxer’s Knuckle

Subluxation or snapping of the tendons on the back of the hand can occur for different reasons. It’s often due to a trauma, such as punching a hard object. That’s why some refer to this injury as ‘Boxer’s Knuckle’. It can also happen when a ball or other object strikes the finger, or from a generalized condition, such as rheumatoid arthritis. The middle finger is the most commonly affected.

When the injured finger is moved the tendon on the back of the hand snaps back and forth. This is an annoying, sometimes painful problem that can greatly affect hand function. If it’s due to an injury that happened no more than 2 weeks previously, a minimally restrictive brace can be tried. This can take two forms: one is a pen-like cylindrical object under the base of the affected digit, on top of the other fingers. This keeps the injured finger’s MP (metacarpophalangeal) joint, the big joint that connects the finger to the hand, from fully flexing. The other type of brace fits into the palm of the hand and also prevents the affected finger’s MP joint from fully flexing.

However, if the tendon subluxation has been going on for over two weeks, or if it’s due to a systemic problem, bracing will probably not work. In these cases, the extensor tendon subluxation is either accepted or treated surgically. Surgically, a strip of the subluxating extensor tendon is used to reconstruct the torn ligament (the sagittal band) that normally keeps the tendon stable. This is an outpatient procedure that is not very painful. It does, however, leave a scar on the back of the hand. After surgery, one of the two braces mentioned above is worn for 4 weeks. The hand can be used, but full MP joint flexion should be avoided for 4 weeks, except under the supervision of a hand therapist.

So if extensor tendon subluxation is causing problems, please know that there is a very simple, effective, and reliable cure for it.