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Equis ISSN 2398-2977

Musculoskeletal: conformation

Contributor(s): Steve Adair, Graham Munroe, Vetstream Ltd, Chris Whitton

Conformation and performance

Introduction
  • Conformation, when used for veterinary purposes, describes anatomical form in relation to biomechanical function.
  • Traditionally, conformation is a subjective analysis of body outline or shape, but attempts to assess a horse's soundness by subjective judgement of skeletal lengths and angles is unreliable.
  • Exact relationship between conformation, performance and soundness is yet to be described.
  • Poor conformation contributes to or causes some lamenesses - it may determine the useful working life of a horse; but it is rare to find a horse with 'perfect' conformation.

Objective measuring techniques

  • Paper markers: glued to palpable and identifiable anatomical landmarks for standard reference points.
  • Measuring tape: to measure circumference of carpus, cannon, chest and some distances.
  • Box level measuring standard: height at withers, back and croup.
  • Cross-bar: for lengths of body, head, limbs; depth of chest, width of breast and pelvis.
  • Calipers: for width of head, cannon bones.
  • Goniometer: joint angles, inclinations of shoulder and pelvis.
  • For comparison with other horses, measurements are expressed in percentage of height of withers; or limb details as percentage of limb length.

Relationship with performance

  • Little scientific information; most studies use objective measurements to compare good and bad performers.
  • Standardbred  Standardbred  : possible that up to 10% of variation in performance can be attributed to conformation; better performers have the following characteristics:
    • Light weight.
    • Tall withers.
    • Normal size hooves.
    • Not tied-in at knees or hocks.
    • Outwardly rotated limb axes.
    • Large shoulder and stifle angles.
  • Showjumpers:
    • Wider breast and pelvis.
    • Greater chest girth.
    • Longer pelvis.
    • Smaller angle between femur and horizontal plane.
    • Compared to dressage horses, showjumpers tend to be higher at the withers.
    • Height at withers and large hock angles may correlate with competitive performance in both types.
  • Warmblood  Dutch warmblood  :
    • Showjumpers and dressage horses: higher at the withers and more sloping scapulae and larger hock angles.
    • Showjumpers: smaller pelvic inclination, smaller hip and fetlock angles.
    • Dressage horses: shorter neck and tibia, larger elbow angle, larger angle between the femur and the horizontal plane.

Relationship with soundness

  • Little scientific information, but relationship between bone health and conformation is of interest to researchers and private practitioners.
  • Divergence from correct conformation   →   increase stress to bones and joints and leads to injury.
  • Standardbred  Standardbred  : better if straight limb and toe-axes; poorer soundness noted if:
    • Very big or small.
    • Relatively short limbs.
    • Abnormally sized hooves.
    • Tied in at knees or hocks.
    • Curby or sickle hocks   Hindlimb: sickle hocks 01    Hindlimb: sickle hocks 02  .
    • Angled fetlocks.
  • In addition, those with hock osteochondrosis   Bone: osteochondrosis  are likely to be heavier, have higher weight gain, a larger circumference of the carpus and cannon; some relationship between outward rotation of hindlimb axes and osteochondrosis lesions in the hock, and plantar fragments in the fetlock.

Body conformation

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Forelimb conformation

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Hindlimb conformation

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Foot conformation

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Terminology

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Further Reading

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