Equis ISSN 2398-2977

Tarsal joint: disease - overview

Synonym(s): Hock joint disease

Contributor(s): Stephen Adams, Graham Munroe, Vetstream Ltd


  • The tarsus is the most common site for hindlimb lameness in performance horses (particularly bilateral).
  • Cause: trauma is the most common cause. 
  • Signs: mild to severe, hindlimb lameness. 
  • Diagnosis: clinical examination and range of ancillary aids including joint and synovial membrane anesthesia Hindlimb: joint anesthesia, ultrasonography Ultrasonography: bone / joints and radiography Hindlimb: radiography
  • Treatment: depends on cause. 
  • Prognosis: depends on cause.





Congenital and neonatal conditions


  • Osteochondrosis is an important cause of tarsal lameness in young horses, especially in the tarsocrural joint Tarsus: osteochondrosis. Fragmentation of the articular cartilage can occur  → fragments in the proximal intertarsal joint.
  • Tarsocrural synovitis bog spavin   Tarsus: tarsocrural synovitis (bog spavin)   which may be acute or chronic has many causes, including osteochondrosis, osteoarthritis, trauma, poor conformation, hemarthrosis, infection and idiopathic.
  • Osteoarthritis: secondary to any tarsal joint injury or without obvious cause; can affect any of the joints in the tarsus - most frequently the centrodistal and tarsometatarsal joints; a common condition in working horses of all types Tarsus: osteoarthritis (bone spavin) Musculoskeletal: osteoarthritis (joint disease).
  • Osseous cyst-like lesions Bone: osseous cyst-like lesions have been recorded in the tarsus, including the medial and lateral malleoli of the distal tibia, intertrochlear groove of the talus, the cranial intermediate ridge of the distal tibia, and the tuber calcanei.
  • Distension of the tendon sheaths of the dorsal aspect of the hock have varying significance and etiology.



  • Tumors are extremely rare.
  • Osteochondroma has been reported in the 3rd tarsal bone, tuber calcanei, MT3 and MT4.

Predisposing factors


  • Conformation may affect kinematics and kinetics of the tarsal joint influencing both performance and soundness:
    • In horses with large tarsal angles (straight hocks), less concussion is absorbed during the impact phase of the stride, which may be a factor in the development of degenerative joint disease. Also the propulsive phase of the stride may be limited, but this may reduce the risk of plantar ligament desmitis. Some people believe that horses with small tarsal angles (sickle hocks) may be predisposed to osteoarthritis of the distal hock joints, curb, plantar distal hock soft tissue injuries and fractures of the central and third tarsal bones.
  • Septic conditions: 


  • The tarsus is a complicated joint comprising the articulations between the distal tibia, the talus, the calcaneus, the small tarsal bones (central, first and second fused, third and fourth) and the second, third and fourth metatarsal bones:
    • The tarsocrural (tibiotarsal) joint is the articulation between the distal tibia and the trochlear of the talus and is where the majority of the flexion/extension movement of the tarsus takes place.
    • The talocalcaneal joint is the articulation between the talus and calcaneus.
    • The proximal intertarsal (talocalcaneal-centroquatral) joint is the articulation between the talus, calcaneus and central tarsal bones.
    • The distal intertarsal (centrodistal) joint is the articulation between the central tarsal bone and the distal row of tarsal bones.
    • The tarsometatarsal (TMT) joint is the articulation between the distal row of tarsal bones and the three metatarsal bones.
    • All joints but the tarsocrural joint are plane or low-motion joints allowing only a small amount of gliding or shear movement.
  • An extensive system of ligaments (collateral - one large and 3 short medially and laterally, one long plantar, one dorsal tarsal, numerous short intertarsal) runs within and between the bones of the entire tarsus and adjacent bones.
  • The tarsus is composed of 4 synovial compartments: 
    • Tarsocrural:
      • Lines: tarsocrural joint + cranial aspect of proximal intertarsal joint.
      • Composed of 4 pouches: dorsolateral, dorsomedial, plantarolateral, plantaromedial.
    • Proximal intertarsal:
      • Lines: talus + calcaneus + plantar aspect of central and 3rd tarsal bones.
      • Communicates with tarsocrural joint.
    • Centrodistal:
      • Lines central + 3rd tarsal bones.
    • Tarsometatarsal:
      • Lines: 2nd + 3rd + 4th tarsal bones + proximal metatarsal bones.
  • Variable physical communication between centrodistal and tarsometatarsal joints between horses and between limbs in the same horse. Injected substances can, however, easily diffuse between these adjacent joints whether there is a physical communication or not.
  • A small percentage of horses have a communication between the tarsocrural joint and the distal tarsal joints.
  • The proximal intertarsal joints communicate with the talocalcaneal joint and the tarsocrural joint, therefore joint conditions of one can affect the others Talocalcaneal joint: disease - overview.
  • All of the joint capsules in the tarsus are superficially located making them particularly susceptible to traumatic wounds and penetrations.
  • See Joint: synovial pathobiology Joint: synovial pathobiology.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Raes E et al (2014) Computed tomographic features of lesions detected in horses with tarsal lameness. Equine Vet J 46 (2), 189-193 PubMed.
  • Lempe-Troillet A et al (2013) Magnetic resonance imaging of plantar soft tissue structures of the tarsus and proximal metatarsus in foals and adult horses. Vet Comp Orthop Traumatol 26 (3), 192-197 PubMed.
  • Daniel A J et al (2012) Comparison of radiography, nuclear scintigraphy, and magnetic resonance imaging for detection of specific conditions of the distal tarsal bones of horses: 20 cases (2006-2010). JAVMA 240 (9), 1109-1114 PubMed.
  • Raes E V et al (2010) Ultrasonographic findings in 100 horses with tarsal region disorders. Vet J 186 (2), 201-209 PubMed.
  • Byam-Cook K L & Singer E R (2009) Is there a relationship between clinical presentation, diagnostic and radiographic findings and outcome in horses with osteoarthritis of the small tarsal joints? Equine Vet J 41 (2), 118-123 PubMed.
  • Vanderperren K et al (2009) Diagnostic imaging of the equine tarsal region using radiography and ultrasonography. Part 1: the soft tissues. Vet J 179 (2), 179-187 PubMed.
  • Vanderperren K et al (2009) Diagnostic imaging of the equine tarsal region using radiography and ultrasonography. Part 2: bony disorders. Vet J 179 (2), 188-196 PubMed.
  • Branch M V, Murray R C, Dyson S J & Goodship A E (2007) Alteration of distal tarsal subchondral bone thickness pattern in horses with tarsal pain. Equine Vet J 39 (2), 101-105 PubMed.

Other sources of information

  • Dyson S J & Ross M W (2003) The Tarsus. In: Diagnosis & Management of Lameness in the Horse. Eds: Ross M W & Dyson S J. Elsevier, Saunders, Missouri. pp 508-526.
  • Sullins K E (2002) The Tarsus. In: Adams Lameness in Horses. 5th edn. Lippincott, Williams & Wilkins, Baltimore. pp 930-987.