Equis ISSN 2398-2977

Proximal sesamoid: sesamoiditis

Contributor(s): Graham Munroe


  • Local inflammation of the proximal sesamoid bones at the site of ligament attachment in racing horses.
  • Two forms of the disease have been described.
  • Signs: can present as an acute, or more usually chronic, forelimb lameness in horses in race training with swelling of the palmar fetlock and palpable pain.
  • Diagnosis: regional anesthesia, radiography and ultrasonography are essential.
  • Treatment: involves rest, modification of work programmes, cold therapy, support bandaging and topical/systemic anti-inflammatory medications.
  • Prognosis: guarded.


Predisposing factors

  • Hard training or racing.
  • Abnormal limb conformation.
  • Previous injury to suspensory apparatus.


  • Term used to describe proliferative or degenerative bony changes of the proximal sesamoid bones.
  • Two forms have been described:
    • Periostitis.
    • Osteitis.
  • 2 forms of seamoiditis have been described.

Periostitis form

  • Acute or chronic injury to the suspensory ligament, distal sesamoidean ligaments and/or palmar/plantar annular ligament of fetlock.
  • Leads to damage at bone-ligament interface (entheses) with proximal sesamoid bones.
  • Osseous metaplasia of fibrous scar tissue and periostitis   →   formation of enthesiophytes + changes in bone contour.

Osteitis form

  • Degenerative condition - is sesamoiditis the right term?
  • Arteriosclerosis and thrombosis of nutrient arteries with subsequent local ischemic necrosis has been suggested as causing demineralized vascular channels within sesamoid bones.
  • Others have suggested that they are normal variations in appearance.
  • Enthesiopathy at the insertion site of the suspensory ligament branches between the nutrient foramina may   →   to the impression of radiolucency and enlargement of vascular channels.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • McLellan J & Plevin S (2014) Do radiographic signs of sesamoiditis in yearling Thoroughbreds predispose the development of suspensory ligament branch injury? Equine Vet J 46 (4), 446-450 PubMed.
  • Zekas L J et al (1999) Characterization of the type and location of fractures of the third metacarpal/metatarsal condyles in 135 horses in central Kentucky (1986-1994). Equine Vet J 31 (4), 304-308 PubMed.
  • Trumble T N et al (1995) Clinical relevance of the microvasculature of the equine proximal sesamaoid bone. Am J Vet Res 56 (6), 720-724 PubMed.
  • Reeves M (1991) Sesamoiditis. JAVMA 199 (6), 682-683 PubMed.
  • Hardy J et al (1991) Clinical relevance of radiographic findings in proximal sesamoid bones of two year-old Standardbreds in their first year of race training. JAVMA 198 (12), 2089-2094 PubMed.
  • Nemeth F (1973) Sesamoiditis in the horse. Tijdschr Diergeneeskd 98 (20), 988-994 PubMed.
  • Nemeth F (1973) The pathology of sesamoiditis. Tijdschr Diergeneeskd 98 (20), 1003-1021 PubMed.