Knuckle pads

Knuckle pads

Knuckle pads are a benign condition characterized by localized thickening of the skin over the interphalangeal and metacarpophalangeal joints of the fingers. The ICD-10 code is M72.1.

Primary (true) knuckle pads and secondary (acquired) pseudoknuckle pads are distinguished. According to Norwegian researchers, the prevalence of the condition reaches 8.8%. According to Norwegian researchers, the prevalence of the condition is 8.8%. There are no gender or ethnic differences.

Primary juvenile knuckle pads typically appear between the ages of 5 and 30. The pathogenesis is unclear, but it is thought to involve fibroblast proliferation. The following subtypes are identified:

  • Idiopathic (sporadic)
  • Familial, inherited in autosomal dominant manner:
    • Bart–Pumphrey syndrome (leukonychia and sensorineural hearing loss)
    • Knuckle pads in combination with esophageal cancer, hyperkeratosis, and oral leukoplakia
    • Familial without other systemic or cutaneous symptoms
  • Associated with other inherited disorders:
    • Keratoderma hereditarian mutilans (Vohwinkel syndrome)
    • Epidermolytic palmoplantar keratoderma with keratin 9 mutation
    • Costa's acrokeratoelastoidosis
    • Congenital palmar fibromatosis
    • Familial pachyonychia
    • Camptodactyly
    • Pseudoxanthoma elasticum
    • Amyotrophy

Primary knuckle pads in mature and elderly individuals are associated with the following conditions:

  • Palmar fibromatosis (Dupuytren's contracture) – found in 40% of cases
  • Fibroplastic induration (Peyronie's disease)
  • Plantar fibromatosis (Ledderhose's disease)

Secondary (acquired) or "pseudoknuckle pads" are associated with repeated local trauma, disturbed regional blood flow, and joint fissures. Terms such as heloderma, subcutaneous fibroma, joint tylosis, or discrete keratoderma are often used to describe them. The following subtypes are identified:

  • Occupational – in carpet weavers, sheep shearers, tailors, etc.
  • Sports-related (sportsman's nodes) – in boxers, footballers, surfers, tennis players, rowers, etc.
  • Childhood – in children who bite their finger joints (bitten calluses, chewing pads) or play video games
  • Russell's sign – formation of knuckle pads due to contact between joint surfaces and teeth during attempts to induce vomiting by placing hands in the mouth in patients with bulimia or anorexia.

The condition is characterized by the appearance of well-defined, rounded, tumor-like growths that develop gradually over several months to years. These growths are firm in consistency, skin-colored or pink in appearance, and may be hypo- or hyperpigmented. They are typically 5-15 mm in diameter (cases as large as 40 mm have been described). The surface of the growths is often smooth, but may be hyperkeratotic or verrucous. The formations are elevated about 3-6 mm above the skin surface and are easily moved in relation to the underlying tissue. The lesions are usually multiple, but may be solitary, and are often symmetrical.

The preferred location for these growths is the areas overlying the dorsum of the interphalangeal (middle and distal) and metacarpophalangeal joints of the fingers, but skin areas over the knee and ankle joints may also be involved. There are no subjective sensations.

The diagnosis is based on the clinical presentation and information from family and professional history. Biopsy may reveal hyperkeratosis, acanthosis, a slight perivascular infiltrate in the dermis, and pronounced connective tissue proliferation. Ultrasound imaging of the growths can also be used for differential diagnosis.

  • Scars
  • Keloids
  • Callus
  • Gottron's papules
  • Fibroma
  • Granuloma annulare
  • Gout
  • Xanthomas
  • Rheumatic nodules
  • Heberden's nodes
  • Milker's nodules
  • Foreign body granuloma
  • Erythema elevatum diutinum
  • Pachydermodactyly
  • Lichen simplex chronicus
  • Warts
  • Papules due to acrocyanosis or frostbite

Treatment is generally not very effective. In cases of secondary involvement, simple removal of irritating factors may lead to spontaneous resolution of the lesions.

There are reports of successful use of 25% urea lotion for 1 month, intralesional corticosteroid injections (significant effect was achieved with a combination of 50 mg/ml 5-fluorouracil with 0.1 ml triamcinolone acetonide), and silicone gel occlusive dressings.

Surgical excision and laser therapy are often associated with unfavorable postoperative complications such as scarring, keloids, and disease recurrence.