A knuckle pad, alternatively known as a Garrod pad or holoderma, refers to a clearly demarcated thickening that occurs over a joint in the finger. It belongs to the category of fibromatoses, which also includes conditions such as palmar fibromatosis (Dupuytren contracture), plantar fibromatosis (Ledderhose syndrome), and pachydermodactyly.

Knuckle pads can develop as a result of an inherited syndrome, sporadic occurrence, or may run in families who have other forms of fibromatosis. Genetic syndromes associated with knuckle pads include Bart-Pumphrey syndrome and Camptodactyly.

The origin of true knuckle pads is a subject of debate, as they may develop as a response to trauma (calluses). It is believed they are callosities caused by repetitive pressure or friction, such as those caused by certain occupations, sports, finger sucking or chewing, or bulimia nervosa.

Furthermore, some experts differentiate between “Dupuytren nodules” and “dorsal cutaneous pads.” While the former exclusively affects patients with Dupuytren contracture, the latter occurs in both individuals with and without the condition.

Typically, knuckle pads appear after the age of 30. In individuals with a family history of knuckle pads, they appear at about the same age within a family. It is important to keep in mind that the age of onset varies between families. In affected children, usually, there is no apparent cause. 

A knuckle pad tends to be more frequently found over the proximal interphalangeal (second) joint rather than over the knuckle (metacarpophalangeal/first joint) or the distal interphalangeal (third) joint. It can appear over one or several joints, and while it is commonly observed in the hands, it may also affect other joints such as the feet and knees.

Knuckle pads are well-defined, smooth, and firm thickenings that are usually flat or more obvious and dome-shaped. These lesions are generally asymptomatic but can be tender or painful for some patients. 

Knuckle pads are usually diagnosed clinically, but may be confused with other conditions such as granuloma annulare, pachydermodactyly, rheumatoid nodules, and synovitis that lead to swollen joints. In these cases, ultrasound can be helpful in distinguishing knuckle pads from synovitis.

Skin biopsy can also aid in the diagnosis of knuckle pads. The histology is expected to show hyperkeratosis and acanthosis of the epidermis, thickening of the dermis, and individual collagen fibers. When knuckle pad is associated with a keratin 9 gene mutation, as seen in epidermolytic palmoplantar keratoderma, suprabasal epidermolysis is also evident.

In general, treatment is not necessary for knuckle pads. However, avoiding repetitive behavior that may aggravate the condition can be beneficial. If the knuckle pads are hyperkeratotic, moisturizers may help. While surgery has been utilized in some cases, it can lead to the development of keloid scars and is therefore not typically recommended.

Centre for Medical and Surgical Dermatology offers unique and personalized treatment options for knuckle pads for each patient.