The document summarizes the anatomy of the equine forelimb and shoulder. It describes the bones, joints, muscles and other structures. Key points include: - The scapula lacks an acromion and has a tuber scapular halfway along its spine. The radius and ulna are fused. - Major muscles include the trapezius, brachiocephalic, latissimus dorsi, and pectoral which act to protract and retract the limb. - The shoulder and elbow joints are synovial joints surrounded by capsules. The carpal joint is a compound joint between the radius/ulna, carpal bones, and metacarpals. - Extrinsic

1. Forelimb and Shoulder
Scapula
 The horse lacks an acromion.
 It has a tuber scapular half way along the spine.
 The scapular cartilage is reasonably extensive compared to
other species.
 supraglenoid tubecle large and separate from glenoid
cavity
Humerus
 Greater tubercle have a cranial & caudal part
 Intermediate tubercle
 lesser tubercle similar size
 Double intertubercular groove.
Radius and Ulna
 The two bones are fused, so all movement is in a sagittal
plane with very little /if any pronation and supination.
 Radius is weight bearing
 The ulna tapers out distally at the middle of the radius
shaft.
 For the proximal quarter of the radius the bones are joined
by ligaments, then there is an interosseous space for the
passage of blood vessels, distal to this the bones are fused.
 The lateral styloid process of the radius is in fact
developmentally the distal end of the ulna. It appears as a
seperate ossification centre in a foal until it fuses at about a
year old.

2. Joints of the Proximal Forelimb
ShoulderJoint
 The joint capsule attaches a very short distance from the
periphery of the articular surfaces.
 The intertubercular (bicipital) bursa lies between the
humeral tubercles cushioning the bicipital tendon.
 The bursa and tendon are held in place by the transverse
humeral retinaculum running between the greater and
lesser tubercles of the humerus.
Elbow Joint
 The joint capsule attaches to the articular surface of the
condyle, the periphery of the olecranon fossa and the
articular cartilage of the trochlear notch of the ulna. It
fuses with the collateral ligaments.
 Paired collateral ligaments attach the epicondyles to the
tuberosities of the radius and ulna.
Structures of the Distal Forelimb
Carpal bones
Carpal bones comprise two rows:
 Proximally, (mediolaterally), radial, intermediate, ulnar
and accessory bones
 Distally, 1st carpal bone is small or absent, II-IV are all
present
Metacarpal and digital bones:
 3rd MC is largest and weightbearing = canon bone
 2nd & 4th = splint bone
 1st= absent or chestnut

3.  5th =absent
 Proximal phalanx= long pastern bone
 Midle phalanx= short pastern bone
 Distal Phalanx = Coffin Bone
Sesamoids:
 2 x Distal sesamoids on the palmar part of MC3
 1 x DIP joint= Navicular bone – guides DDFT over DIP
joint
Joints of the Distal Forelimb
Carpal Joint
The carpal joint is a compound joint composed of:
 The (antebrachiocarpal joint) between the radius/ulna
and the proximal carpal bones – most movement
 The( middle carpal joint) between the two rows of carpal
bones
 The( carpometacarpal joint) between the distal carpal
bones and the proximal metacarpals- least movement
The joint is a synovial joint, comprised of a common outer
fibrous capsule and three inner synovial pouches, one for each
joint.
 (Collateral ligaments) extend from the radius to the
metacarpal bones on the medial and lateral aspect of the
carpus.
 The carpal canal houses both the superficial and deep
digital flexor tendon within a common synovial sheath.

4. Muscles of the Forelimb
ExtrinsicMusculature
.
Trapezius:
 Origin: mid-dorsal raphe and supraspinous ligament
 Insertion: spine of the scapula
 Body: two parts, cervical and thoracic separated by
aponeurosis
 Action: raises scapula against the trunk and swings
cranially to advance the limb
Brachiocephalicm.:
 Origin: mastoid process of temporal bone, nuchal crest,
wing of atlas, transverse processes of the 2nd-4th cervical
vertebrae
 Insertion: deltoid tuberosity and crest of humerus
 Actions:
o advances the limb and extends the shoulder joint
when limb is in motion
o draws head and neck ventrally when limb is fixed
Latissimus dorsi:
 Origin: thoracolumbar fascia
 Insertion: teres tuberosity of the humerus
 Actions: antagonist to the brachiocephalic m.
o cranial fibers strap scapula to the chest
o retracts free limb and flexes shoulder joint
o draws trunk forward over the fixed limb

5. Pectoral muscle.:
 Two superficial parts, cranial and caudal
o Origin: cranial sternum
o Insertion:
 cranial (descending): crest of the humerus
distal to the deltoid tuberosity
 caudal (transverse): covers elbow joint to
insert on the medial fascia of the forearm
o Action: adduct the forelimb, assist in protraction and
retraction
 One deep part (pectoralis profundus), with cranial and
caudal parts
o Origin: ventral sternum and adjacent cartilage
o Insertions:
 cranial (subclavius): supraspinatus m.
 caudal (pectoralis ascendens): lesser tubercle of
the humerus
o Actions:
 slinging trunk between forelimbs
 may also retract free limbs
 draw trunk forward when limb is fixed
Serratisventralis:
 Origin: C4 to 10th rib
 Insertion: medial scapula and scapular cartilage
 Action: supporting the weight of the trunk
o reinforced by strong fascia
o cervical portion can retract the limb
o caudal portion can advance the limb

6. Rhomboids:
 Origin: median connective tissue from poll to withers,
lying deep to the trapezius
 Insertion: dorsal border and adjacent scapula
 Action: retracting the limb, may also raise limb
Intrinsic Musculature
Muscles of the Shoulder
 Lateral:
o Origin: the fossae of the scapula
o Insertion: both tubercles of the humerus
o Action: brace the shoulder
o Clinical significance : bursa between the tendon of
the infraspinatus and lateral tubercle of the humerus
can be the site of inflammation
 Medial:
o Supscapularis: Subscapular n. from the brachial
plexus
 Origin: Deep surface of the scapula
 Insertion: medial tubercle of the humerus
 Action: braces medial shoulder joint, potential
adductor
o Coracobrachialis : Musculocutaneous n. of the
brachial plexus
 Origin: medial supraglenoid tubercle
 Insertion: proximal shaft of the humerus
 Action: fixator
 Caudal (Flexors
o Deltoids:
 Origin: caudal border and spine of the scapula
 One head in the horse and two in species
with an acromion (site of second origin)
 Insertion: deltoid tuberosity on the humerus

7. Teres Major:
 Origin: dorsal part of the caudal scapula
 Insertion: teres tuberosity midway down
humerus
o Teres Minor:
Ventral extremety of scapula.it is inserted in the teres minor
tuberosity .It leads to flexion of the shoulder.
Muscles of the Elbow
Extensors:
 Triceps brachii:
o Long head: caudal margin of the scapula
o Lateral and medial heads: shaft of the humerus
o Insertion: olecranon, proteced by tricipital bursa
against the bone and subcutaneous bursa against the
skin
 Tensor fasciae antebrachii:
o Overlies triceps extending from scapula to olecranon
 Anconeus:
o Origin: distal humerus
o Insertion: lateral olecranon
Flexors:
 Biceps brachii
o Origin: supraglenoid tubercle of the scapula
o Insertion: medial tuberosity of proximal radius and
adjacent ulna
o Runs through the intertubercular groove of the
humerus
 Brachialis
o Origin: proximocaudal humerus
o Insertion: spirals to insert next to biceps

8. Muscles of the Carpal and Digital Joints
Extensors: Radial n. from the brachial plexus Craniolateral
position on the forearm Almost all originate from the lateral
epicondyle of the humerus
 Extensor carpi radialis: most medial, metacarpal
tuberosity
 Ulnaris lateralis: most lateral, inserts on accessory carpal
bone
 Extensor carpi obliquus:
o Origin: cranial radius
o Insertion: head of the metacarpal II
 Common Digital Extensor :
o Insertion: extensor process of the distal phalanx
 Lateral Digital Extensor:
o Insertion: dorsal proximal phalanx
 Flexors: Median or Ulnar n. of the brachial plexus. Caudal
position on the forearm
 Originate from the caaudal medial epicondyle of the
humerus
 Flexor carpi radialis: most medial, inserts on proximal
part metacarpal II
 Flexor carpi ulnaris: most lateral, inserts on the accessory
carpal bone
 Superficial Digital Flexor:
o Insertion: promial extremity of middle phalanx,
distal extremity of proximal phalanx
 Deep Digital Flexor:
o Passes through carpal canal before branching and
continues to palmar distal phalanx.

9. With all pleasure