Knuckle pads are round, hard, callous-like skin lesions that develop on the middle knuckle or the distal knuckle located near the tip of the finger. These pads are produced by a thickening and hardening of the epidermis, the most superficial layer of skin. They are often referred to as heloderma because the pads look like the scaly skin of a Gila monster.
Benign and typically painless, knuckle pads do not usually hinder finger movement. The main issue with these pads is cosmetic. Pads on the knuckle are fairly noticeable due to their size and because the appearance of the pads is sometimes one shade lighter than the normal skin tone. The pads can be as small as 0.1 inch (3mm) or as large as 0.8 inch (20mm) and cover the entire knuckle.
The exact cause of this cutaneous condition is unknown. Knuckle pads are associated with repeated trauma to the knuckles or picking at the knuckles following an injury or an insect bite. They are often found on the hands of boxers and people who engage in physical work that frequently traumatizes fingers. Children are prone to this condition since they are more likely to pick at an injury or bite.
Knuckle pads are sometimes found on 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 on the palm of the hand. These pads are also associated with camptodactyly, a condition where the fingers become progressively and permanently bent. The propensity to develop these pads tends to run in families, suggesting that there is a genetic component to the manifestation of this condition.
These skin lesions will sometimes spontaneously shrink and disappear over time. This is often true when the knuckle pads were caused by trauma or picking and these issues are stopped. If heloderma persists, there are a few treatment options. Knuckle pads can be treated with corticosteroid injections, which tenderizes the pads and gradually reduces their size.
When this condition does not respond to steroid injections and does not shrink on its own, the last resort is outpatient surgery. During surgery, a local anesthesia is used to numb the finger and then the thickened, superficial skin is cut away. Great care must be taken following the surgery to prevent trauma to the wound and keep another pad from growing over the surgical site.