KnotesFree Orthopaedic & FRCS Notes
Foot and Ankle

Subungual Exostosis

Foot and Ankle

Aetiology

  • Fibrocartilaginous exostosis occurring from distal phalanx of the big toe
  • May also occur in hand or lesser toes – rare
  • Many are actually osteochondromas with a hyaline cartilage cap

Clinical Features

  • Pain and breach of the nail
  • Inflammation and elevation around the medial nail fold (more common)
  • Often previously misdiagnosed as an ingrown toenail due to similar appearance

Differential Diagnosis

  • Ingrown toenail
  • Subungual melanoma or Squamous Cell Carcinoma (SCC)
  • Glomus tumor

Imaging

X-ray (XR)

  • Clearly shows exostosis

Management

  • Excision
  • Try to preserve nail fold and bed, but usually not possible
  • Often leads to an abnormally shaped nail
  • Recurrence rate: 10% despite complete excision

Related FRCS revision notes

Ingrowing ToenailAchilles TendinopathyHallux RigidusFoot DropFreiberg’s InfractionOsteochondral Lesions of the Talus

Linked from

← Foot and Ankle← Ingrowing Toenail

Written/reviewed by Kishore Puthezhath

Professor of Orthopaedics and Consultant Paediatric Orthopaedic Surgeon

FRCS (Tr & Orth) revision resource

Reviewed: September 2026

Core revision references: Miller's Review of Orthopaedics; Campbell's Operative Orthopaedics; Orthobullets. Current specialty guidelines are linked within individual notes where applicable.