Fetlock joint of forelimb

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Ox

There are two Fetlock joint of forelimb for each limb. Each is a ginglymus formed between the distal extremity of the large metacarpal, the proximal extremity of the first phalanx below and the proximal sesamoids behind.

  • Ligaments
    1. The joint has a capsular, collateral and sesamoidean ligaments.
    2. The capsular ligaments enclose the joints and adherent to the extensor tendons passing over the metacarpal.
    3. The collateral ligaments are in the form of axial and abaxial ligaments.
    4.  The abaxial ligaments extend from the lateral aspects of the distal extremity of the large metacarpal to the abaxial sesamoids and the proximal extremity of the first phalanx below.
    5. The axial ligaments arise common from the cleft of the large metacarpal bone and each spreads out on the cleft of the large metacarpal bone. It then spreads out and attached to the proximal part of the interdigital space of the first phalanx, where its fibres blend with the superior interdigital ligament.
    6. The sesamoidean ligaments are superior, inferior, collateral and inter sesamoidean.
    7.  The superior sesamoidean or suspensory ligament (musculus interossei) arises from the volar face of the distal row of carpal bones and the proximal extremity of the large metacarpal descends on the volar face of the latter and divides about its middle into two branches-anterior and posterior.
      • The posterior branch soon bifurcates at the distal end of the large metacarpus and each unites with one the divisions of the tendon of the superficial flexor of the digit behind the fetlock to form a ring for the passage of the tendon of the deep flexor of the digit.
      • The anterior branch divides into six branches, which are in three pairs-abaxial, middle and axial.
        • The abaxial and middle slips are attached to the abaxial and axial sesamoids of each digit. The slips passing to the abaxial sesamoids detaches a slip which passes downwards the and forwards on the abaxial face of each digit to join the extensor tendon of the respective digit on the dorsal aspect.
        • The two axial slips pass into the cleft of the large metacarpal bone enter the inter-digital space and here join the same extensor tendons.
      •  The suspensory ligament prevents extensive dorsal flexion of the fetlock joint and its slips prevent excessive volar flexion. In the young, the superior sesamoidean ligament is muscular while in the adult it becomes fibrous.
    8. The inter-sesamoidean ligaments are three for each limb has three such ligament placed between four sesamoids.
    9. The collateral sesamoidean ligaments extend between the corresponding faces of abaxial sesamoids to the proximal extremity of the first phalanx and the lateral aspects of the large metacarpal.
    10. The inferior sesamoidean are two straight and two oblique.
      • The straight ones are vertical, connecting the bases of the sesamoids to the upper end of the first phalanx.
      • The oblique ligaments are placed deeper, also extended from the base of the sesamoids, they cross and get attached to joint the first phalanx.
  • Motion
    1. Extension and flexion.
Horse
  • There is only one metacarpo phalangeal joint for each limb and hence there are only two collateral and one inter-sesamoidean ligament for the whole joint.
  • The inferior sesamoidean ligament is made up of three parts-superficial, middle and deep.
    • The superficial or straight (Y-shaped) connects bases of two sesamoids to the first phalanx.
    • The middle one connects the sesamoids to the ‘V’ shaped area on the volar face of the second phalanx.
    • The deep or cruciate (X-shaped) ligament connects the base of each sesamoid to the phalanx. The suspensory ligament passes in the channel between the large and small metacarpal bones and divides above the fetlock into two branches. Each of these is attached to the superior and lateral faces of each sesamoid and then passes obliquely forward and downward to the dorsal face of the first phalanx and joins the tendon of the extensor pedis to form broad ligament.
Dog
  • There are five metacarpo-phalangeal joints in the dog.
  • Each joint has its own capsule and indistinct collateral ligaments.
  • A small dorsal sesamoid bone occurs in the anterior of each capsule over which the corresponding extensor tendon plays.
  • The cruciate inferior sesamoidean ligaments are present on the volar aspect.
  • The suspensory ligament is placed by interosseous muscles.
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