Joints of the Thoracic Limb
Articulation of the Thoracic Limb to the Trunk:
The forelimb connects to the skeleton via muscles, tendons, and fascia, forming a synsarcosis.
This connection lacks a conventional joint - the ability to move.
Shoulder (Humerus) Joint:
A spheroidal (ball and socket) synovial joint formed by the humeral head and the glenoid cavity of the scapula.
Movement: Universal, but limited primarily to hinge joint type of movement (flexion and extension) due to surrounding muscles. Carnivores have limited rotation, abduction, and adduction, unlike other domestic animals.
Ligaments:
Collateral ligaments are absent.
Medial and lateral glenohumeral ligaments are present in all species.
Ungulates possess an additional coracohumeral ligament.
Carnivores have a transverse humeral ligament.
Joint Capsule Pouches: Differ across species.
Horses and oxen: three cranial and two caudal pouches.
Carnivores: two cranial and one caudal pouch.
Bicipital Tendon:
In carnivores, pigs, and sheep, the joint capsule partially surrounds the bicipital tendon, forming a synovial sheath.
In horses and oxen, an intertubercular bursa replaces this sheath.
Elbow Joint:
A hinge (ginglymus) joint allowing primarily extension and flexion.
Formed by the humeral condyle, the trochlear notch of the ulna, and the radial head of the radius.
Movement Restriction: Prominent olecranon tuber, ridges, and grooves on trochlear surfaces prevent lateral or rotational movement.
Extension Range:
Cats and dogs: up to 140 degrees.
Large animals: limited extension and flexion.
The elbow joint in horses and oxen is known as the snap joint.
Supporting Ligaments:
Lateral (radial) collateral ligament (with cranial and caudal parts, except the horse which lacks the caudal part).
Medial (ulnar) collateral ligaments.
Olecranon ligament (in small animals like dogs and cats) reinforces the joint capsule.
Radial Joints:
In carnivores, there are two separate synovial articulations:
Proximal radial joint: between the circumference of the radius and the radial notch of the ulna.
Distal radial joint: between the articular circumference of the ulna and the ulnar notch of the radius.
Movement:
Large animals: rotational movement is restricted.
Cats and dogs: limited supination in dogs and up to 100° supination in cats.
Radius and Ulna Articulation:
In pigs, the radius and ulna are firmly articulated, forming an amphiarthrosis (immovable joint).
In oxen and horses, the proximal parts of the radius and ulna are united by fibrous and elastic tissues, which ossify with age, leading to fusion.
Supporting Ligaments (Proximal Radial Joint):
Interosseous membrane of the antebrachium.
Annular ligament and interosseous ligament of the antebrachium.
Supporting Ligaments (Distal Radial Joint):
Radioulnar ligament (distinct in dogs).
In cats, the radioulnar ligament consists of fibers embedded in the joint capsule.
Distal Radial Joint in Carnivores and Pigs: A proximal extension of the antebrachiocarpal joint.
Articulation of the Manus (Carpal Joints):
Composed of four major joints:
Ulnocarpal and radiocarpal joint: between the radius, ulna, and proximal carpal bones.
Middle carpal joint: between the proximal and distal carpal bones, including the joint formed by the accessory carpal joint.
Intercarpal joint: between individual carpal bones.
Carpometacarpal joints: between the metacarpal bones and the distal carpal bones.
Supporting Ligaments:
Long lateral and medial carpal collateral ligaments (absent in the shoulder joint).
Short ligaments: vertical, horizontal, and short ligaments.
Dorsal carporadiocarpal ligament.
Lateral ulnar and accessory carpal ligament.
Collateral Ligaments in Carnivores: Carnivores lack a long, continuous collateral ligament seen in other species.
Short Transverse Ligaments: Support the proximal rows of carpal bones.
Carpometacarpal Ligaments: Support the articulation between distal carpal bones and metacarpals.
Accessory Ulnar Ligament: Supports the articulation between the accessory carpal bone to the ulnar carpal bone.
Phalangeal Joints:
Three major joints:
Metacarpophalangeal joint (fetlock joint in ungulates): articulation of the metacarpals to the first phalanx.
Proximal interphalangeal joint (pastern joint in ungulates): between the long and short pastern in ungulates.
Distal interphalangeal joint (coffin joint in ungulates): between the short pastern and the coffin bone.
Carnivores:
Metacarpophalangeal joints: five joints between metacarpals and first phalanx.
Proximal interphalangeal joints: between proximal and distal phalanx.
Distal phalangeal joint: at the end of the digit.
Ungulates (Hoofed Animals):
Metacarpophalangeal Joint (Fetlock):
Formed by sesamoid bones, long pastern, and metacarpal bone.
Hinge joint between the distal end of the metacarpal bone, the proximal end of the first phalanx, and the sesamoid bones.
Proximal sesamoid bones at the back.
Supporting ligaments: collateral and sesamoid ligaments (proximal, middle, and distal).
In ruminants and horses, the proximal ligament is replaced by a suspensory ligament.
Interdigital ligaments.
Fetlock Joint of Ruminants:
Formed by the trochlea of the third and fourth metacarpal bones to the articular surfaces of the first phalanges.
Two proximal sesamoid bones on the palmar surface.
Supported by proximal interdigital, abaxial, and axial collateral ligaments.
Fetlock Joint of the Horse:
Formed by the articulation between the third metacarpal bone (cannon bone) and the proximal articular surface of the first phalanx and the proximal sesamoid bone.
Movements: flexion and extension, with partial flexion at a standing position.
Ligaments: collateral and sesamoid ligaments (proximal, middle, and distal).
Proximal Interphalangeal Joint (Pastern Joint):
A subtle joint with concavo-convex articular surfaces.
Ligaments: collateral, palmar, and additional ligaments.
In ruminants, located between the articular surfaces of the first and second phalanges.
Ligaments: abaxial and axial collateral ligaments and palmar ligaments.
Distal Interphalangeal Joint (Coffin Joint):
Similar to the proximal interphalangeal joints in carnivores.
Ligaments: interdigital ligaments, dorsal ligaments, lateral collateral ligaments, and abaxial collateral ligaments.
In the horse, formed by the distal trochlea of the second phalanx, the third phalanx, and the distal sesamoid (navicular) bone.
Synovial bursa between the navicular bone and the deep digital flexor tendon.
Ligaments: medial and lateral collateral ligaments, ligaments of the distal sesamoid bones, and ligaments of the cartilages of the distal phalanx.
Carnivores:
Metacarpophalangeal joints: five metacarpophalangeal joints formed by the distal trochlea of metacarpal bones one to five, proximal sesamoid bones, and articular surfaces of the first phalanges.
Proximal ligaments are replaced by interosseous muscles.
Ruminants:
Fetlock joint formed by the trochlea of the third and fourth metacarpal bones to the articular surfaces of the first phalanges.
Two proximal sesamoid bones on the palmar surface.
Supported by proximal interdigital ligaments and abaxial and axial collateral ligaments.
Horse:
Fetlock joint formed by the articulation between the third metacarpal bone (cannon bone) and the proximal articular surface of the first phalanx and the proximal sesamoid bone.
Movements include flexion and extension, with partial flexion at a standing position.
Ligaments include collateral and sesamoid ligaments (proximal, middle, and distal).
Proximal Interphalangeal Joint (Pastern Joint): Formed by the proximal end of the second phalanx and the distal end of the first phalanx.
Ligaments: collateral and palmar ligaments.
Coffin Joint: A subtle joint similar to the proximal interphalangeal joints in carnivores.
Formed by the distal trochlea of the second and third phalanges and the distal sesamoid or navicular bone.
Synovial bursa between the navicular bone and the deep digital flexor tendon.
Ligaments: medial and lateral collateral ligaments, ligaments of the distal sesamoid bones, and ligaments of the cartilage cartilages of the distal phalanx.