Knee joint

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Knee joint is composite joint consisting of-

  1. Radio-ulnar-carpal  articulations
  2. Carpal articulations
    • Proximal carpal  articulations
    • Intercarpal articulations
    • Distal carpal articulations
  3. Carpo-metacarpal articulations.  

The joint as a whole is  having common ligaments and special ligaments

Common ligaments
  1. Capsular ligament is a loose sac. Its anterior part is called dorsal carpal ligament, which covers the joint in front and is adherent to the extensor tendons passing over it. The posterior part is called as volar carpal ligament covers the joint behind and its posterior face forms the anterior wall of the carpal sheath.
  2. Lateral and Medial carpal ligaments which arise from the distal extremity of the radius and ulna, pass down adherent to the carpal bones and are attached to the upper extremity of the large metacarpal below on the lateral and medial aspects of the joint.
  3. The carpal sheath or canal is formed by the volar capsular ligament in front and by the volar annular ligament behind, which extends from the posterior border of accessory carpal to the medial aspect, blending with the medial ligament of the carpus. The canal is lined by synovial membrane and serves for the passage of tendons of flexor perforans, deep division of flexor perforatus, median nerve, ulnar artery and vein.
Special ligaments

There are large number of special ligaments connecting the various bones of the carpal joint-

  1. Radio-ulnar carpal articulation
    • It is diarthrosis between the lower extremity of the radius, styloid process of ulna and upper row carpal bones. The radius articulates with all the three bones and the ulna articulate with ulnar carpal only.
    • Ligaments
      • One oblique and three posterior ligaments.
      • Oblique ligament  connects the radius and ulnar carpal obliquely on the dorsal aspect.
      • The  three posterior ligaments connects  the (1) radius and radial carpal (2) radius and intermediate carpal (3) ulnar and accessory carpal on the volar aspect. 
  2. Carpal articulations
    • Proximal carpal articulations
      • They are also diarthroses and between the bones of upper row.
      • Ligaments  
        • There are three anterior, two posterior and three interosseous ligaments.
        • The  three anterior ligaments are connecting viz.,  (1) radial carpal to intermediate carpal (2) intermediate to ulnar carpal (3) ulnar carpal to accessory carpal on the dorsal aspect.
        • The posterioe ligaments connects the(1) Intermediate to ulnar metacarpal (2) Ulnar carpal to accessory carpal on the volar aspect.
        •  Interosseous ligaments that connect adjacent bones.
    • Inter-carpal articulations
      • They are arthroid and between the bones of proximal row and distal row.
      • Ligaments
        • There are two oblique and three posterior ligaments.
        • The two oblique ligaments are connecting on the dorsal aspect viz.,(1)obliquely radial carpal and fourth carpal (2) ulnar carpal and fourth carpal fibres also extend below to the large and small connect metacarpal bones.
        • The three posterior ligaments are connecting on the volar aspect (1) radial carpal to fused second and third carpal. (2) ulnar carpal to fourth carpal (3) accessory carpal to fourth carpal
    • Distal carpal articulations
      • They are arthroid between the fused second and third carpal and fourth carpal.
      • Ligaments
        • A ligament connectssecond and third carpal to fourth carpal on dorsal aspect
        • An interosseous ligament
  3. Carpo-metacarpal articulation
    • They are formed between the distal row of carpal bones and proximal extremity of the metacarpal bone.
    • Ligaments
      • There are two anterior, two posterior and two interosseous ligaments. However, these short ligaments are sometime weak or inconstant in number.
      • The anterior ligaments connects  (1) second and third carpal to on large metacarpal (2) fourth carpal to large metacarpal on the dorsal aspect.
      • The posterior ligaments connects . (1) ulnar carpal to large metacarpal (postero lateral) (2) second and third carpal to large metacarpal (3) fourth carpal to large metacarpal on the volar aspect.
      • An interosseous ligament connects second and third carpal to large metacarpal. Two anterior and posterior ligaments hold the accessory carpal.
    • Synovial membranes
      • There are three large and one small synovial membrane.
    • Motion
      • Extension and flexion and to a small extent abduction and circumduction in the radio-ulnar carpal.
      • In the other joints motion is inappreciable.
Horse
  • There is minor difference due to the increased number of the carpal bones.
  • There are two other important ligaments peculiar to the horse called superior  and inferior check ligaments.
  • The superior check ligament (supracarpal) arises from the dorsal part of the medial border of the radius and is inserted to the tendon of the superficial flexor of the digit above the carpus.
  • The inferior check ligament (subcarpal) is a continuation of the volar capsular ligament of the carpus. It joins the tendon of the deep flexor of the digit about midway down the metacarpus. The check ligaments assist the flexor tendons after severe exertion to keep them tight and prevent flexion.
Dog
  • There are differences due to variation in the number of bones of the carpus.
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