Equis ISSN 2398-2977

Tarsus: capped hock

Contributor(s): Graham Munroe, Jessica A Kidd

Introduction

  • A swelling over the point of the hock which does not cause lameness and which is a cosmetic issue. It must be distinguished from other hock swellings which do cause lameness and are more serious conditions.
  • Cause: persistent, usually self-inflicted, direct blunt trauma to the subcutaneous bursa over the point of the hock leading to inflammation within the bursa and surrounding subcutaneous tissue/skin.
  • Signs: swelling over point of hock, often soft fluid-filled and non-painful; no lameness.
  • Diagnosis: clinical history and signs with palpation; ultrasound examination +/- radiographs of plantar hock.
  • Treatment: acute inflammatory treatments in early cases; intrabursal corticosteroids +/- pressure bandaging; prevention of trauma.
  • Prognosis: good for athletic soundness; guarded for cosmesis.
Print off the Owner factsheet on Capped hock to give to your clients.

Pathogenesis

Etiology

  • There are 3 potential bursae at the point of the hock:
    • The intertendinous bursa (also called the calcaneal bursa) lies between the dorsal surface of the SDFT and the gastrocnemius tendon.
    • The gastrocnemius bursa is located dorsal to the insertion of the gastrocnemius tendon on the tuber calcanei.
    • The variable present subcutaneous bursa located just distal to the tuber calcanei.
    • There are variable degrees of connection between these structures.
  • Whilst all three bursae may be involved in tarsal bursitis   Calcaneal bursa: bursitis  , a 'capped hock' is an acquired swelling at the point of the hock (tuber calcanei) related to persistent direct blunt trauma to the area. The swelling involves a distension of the already present subcutaneous bursa, or development of an acquired bursa over the top of the tuber calcanei. Both occur following repetitive trauma such as stable wall kicking or leaning backwards on its hocks during traveling.
  •  Infection due to wounds or focal penetrations are rare in these cases and if they occur, should be treated similarly to other calcaneal bursal infections    Calcaneal bursa: bursitis  .
  • 'Deep capped hock' is a misleading term used to describe distension of the intertendinous bursa and is considered elsewhere   Calcaneal bursa: bursitis  .
  • In some cases the chronic repetitive trauma leads to minimal fluid distension of any of the bursae, but instead causes a marked thickening of the skin and subcutaneous fibrosis to occur.
  • There is usually no associated lameness and they are often considered as cosmetic blemishes.
  • Uni- or bilateral cases can occur.

Predisposing factors

General
  • External trauma to the point of the hock, usually persistent and repetitive.

Specific

  • Persistent kicking of the walls or door of the stable.
  • Kicking or banging the hocks against partitions or doors in trailers or horse transporters.
  • Poor or inadequate bedding in the stable.

Pathophysiology

  • Trauma leads to inflammation of the already present subcutaneous bursa or the formation of an acquired bursa in this position.
  • The inflammation leads to an increased synovial fluid production within the bursa.
  • There may be chronic changes in the skin with thickening and fibrosis; in some cases there is additional fibrosis subcutaneously.

Timecourse

  • Often the fluid swelling appears suddenly and then may persist for long periods of time.
  • Spontaneous resolution may occur if the inciting factors are removed.
  • The degree of fluid swelling can vary over time and will fluctuate with the amount of trauma that persists.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references fromPubMedandVetMedResource.
  • Post E M, Singer E R & Clegg P D (2007)An anatomic study of the calcaneal bursae in the horse.Vet Surg36(1), 3-9PubMed.
  • Post E Met al(2003)Retrospective study of 24 cases of septic calcaneal bursitis in the horse.Equine Vet J35(7), 662-668PubMed.
  • van Pelt R W & Riley W F Jr (1986)Traumatic subcutaneous calcaneal bursitis (capped hock) in the horse.JAVMA153(9), 1176-1180PubMed.


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