Knuckle pads are circumscribed, keratotic, fibrous growths over the dorsa of the interphalangeal joints. Knuckle pads are well-defined, round, plaque-like, fibrous thickening that may develop at any age, and grow to be 10 to 15mm in diameter in the course of a few weeks or months, then persist permanently. Knuckle pads are sometimes associated with Dupuytren's contracture

Dupuytren's contracture

Dupuytren's contracture , is a fixed flexion contracture of the hand where the fingers bend towards the palm and cannot be fully extended...

 and camptodactyly

Camptodactyly

Camptodactyly is a medical condition involving fixed flexion deformity of the interphalangeal joints of the little finger. This involves permanent flexure of one or more phalanges...

, and histologically, the lesions are fibromas.