Knuckle pads are round, hard, callous-looking skin lesions that develop on the middle knuckle or distal knuckle located near the fingertip. These pads are produced by a thickening and hardening of the epidermis, the most superficial layer of the skin. They are often referred to as heloderma because the pads resemble the scaly skin of a Gila monster.
Benign and typically painless, knuckle pads do not usually interfere with finger movement. The main problem with these pads is cosmetic. The pads on the knuckles are quite noticeable due to their size and because the appearance of the pads is sometimes a shade lighter than normal skin tone. Knuckle pads can be as small as 0.1 inch (3 mm) or as large as 0.8 inch (20 mm) and cover the entire knuckle.
The exact cause of this skin condition is unknown. Knuckle pads are associated with repeated trauma to the knuckles or knuckle bites after injury or an insect bite. They are often found in the hands of boxers and people doing physical labor that frequently traumatizes the fingers. Children are prone to this condition as they are more likely to bite an injury or bite.
Knuckle pads are sometimes found in people with bulimia who use their fingers or knuckles to induce vomiting. This skin problem is also strongly associated with Dupuytren's contracture, a condition in which scar tissue develops in the palm of the hand. These pads are also associated with camptodactyly, a condition in which the fingers progressively and permanently bend. The propensity to develop knucklebones tends to run in families, suggesting that there is a genetic component to the manifestation of this condition.
These skin lesions sometimes shrink spontaneously and disappear over time. This is usually true when the knuckle pads were caused by trauma or a puncture and these problems have stopped. If heloderma persists, there are a few treatment options. Knuckle pads can be treated with corticosteroid injections, which soften the pads and gradually reduce their size.
When this condition does not respond to steroid injections and does not shrink on its own, outpatient surgery is the last resort. During surgery, a local anesthetic is used to numb the finger, and then the thickened superficial skin is cut away. Great care must be taken after surgery to avoid trauma to the wound and to prevent another pad from growing over the surgical site.