Joints
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Shoulder joint
 Medial/lateral collateral ligaments
 Transverse humeral ligament
Elbow joint
 Lateral collateral ligament (origin of the lateral digital extensor m.)
 Medial collateral ligament (origin of the pronator teres m.)
 Annular ligament (ring-shaped structure around the head of the radius)
 Oblique ligament (cranial surface of elbow joint; may function synergistically with medial collateral
ligament)
Hip joint
 Sacrotuberous ligament
 Ligament of the head of the femur
 Transverse acetabular ligament
Stifle joint
 Connect tibia to femur
 Cranial cruciate ligament
 Caudal cruciate ligament
 Medial collateral ligament
 Lateral collateral ligament
 Connect menisci to femur and tibia
o Transverse meniscal ligament
 Connects cranial ends of menisci
o Menisco-femoral ligament
 Attaches lateral meniscus to distal femur
 Allows lateral meniscus more mobility
 Connect patella to fabellae
o Lateral femoropatellar ligament
o Medial femoropatellar ligament
 Patellar ligament
o Connects patella to tibia (distal to patella)
 Tendon of the quadriceps m.
o Connect the patella to the femur (proximal to patella)
What happens in rupture of the cranial cruciate ligament?
Results in “anterior (or cranial) drawer syndrome”, where cranial displacement of the tibia in relation to distal femur and
medial rotation of the tibia results in injuries to the medial meniscus. Injuries result only to the medial meniscus because it,
unlike the lateral meniscus, is attached to the medial collateral ligament and cannot move away to avoid pressure (The
lateral meniscus is not attached to the lateral collateral ligament because popliteus tendon of origin runs between the lateral
meniscus and lateral collateral)
What is the labra articularia and 2 joints that exhibit this?
Well-defined marginal cartilage (fibrocartilage) that cushions the joint. Both the shoulder and hip joint exhibit this.
Vertebrae
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Vertebral formula for dog and cat
 C7, T13, L7, S3, Ca~20
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Each vertebrae consists of 3 structures
 Body
o Dorsal aspect usually exhibits 2 foramina for blood vessels
 2 transverse processes
 Arch enclosing the vertebral foramen
o Lateral walls of the arch are formed by pedicles
o Roof of the arch is formed by lamina
Clinical Note***Pedicalectomy involves removing part of the pedicle to relieve pressure on the spinal nerves.
Laminectomy involved removing the lamina to reduce spinal cord compression (i.e. from disc herniation)
Cervical vertebrae
- 7 (in dog and cat)
 C7
o Lacks transverse foramina
o May present small articular facet (demifacet) for head of 1 st rib
- Atlas (C1)
 Body is dens of the axis
 Cranial articular surface
o Two, large oval cavities that articulate with occipital condyles of the skull (cranial articular
fovea)
 Caudal articular surface
o Two articular facets that articulate with the cranial articular surfaces of the axis
 On each wing there are two foramina
o Lateral vertebral foramen (rostral)
 transmits 1st cervical n.
o Transverse foramen (caudal)
 transmits the vertebral artery and vein
- Axis (C2)
 Dens
o Rod-shaped cranial process
o Represents the body of the atlas during early development
o Articulates with fovea on floor of vertebral foramen of atlas
o Lies ventral to spinal cord
 Spinous process
 Transverse processes
o Each has transverse foramen at base
 Cranial vertebral notches
o With atlas, form the intervertebral foramen
- Atlanto-occipital joint
 Dens of axis is attached to occipital bone by 3 ligaments
o Apical ligament
 Extends from dens to floor of foramen magnum (skull)
o Alar ligaments (paired)
 Extend from dens to medial aspect of occipital condyles
o Transverse atlantal ligament
 Prevents the dens from moving toward the spinal cord
 Extends from dorsal aspect of dens to floor of the atlas
- Atlanto-axial joint
 Dorsal atlanto-axial ligament
o Extends from dorsal aspect of atlas to the spinous process of axis
Clinical note***During early development, the dens is formed from the fusion of cells destined to form the body of the atlas
and cells of the axis body. Congenital malformation of the dens can lead to disorders, instability of the atlanto-axial joint,
and compression of the spinal cord. These are more common in toy or miniature dog breeds. The most severe compression
of the spinal cord results from an intact dens with absence or rupture of the transverse atlantal ligament. Affected animals
may show signs of pain in upper cervical region and present varying degrees of motor dysfunction. Treatment consists of
stabilization of joint (wiring spinous process of axis to vertebral arch of atlas) and decompression of spinal cord.
Clinical note***Proatlas of the dens (tip of dense exhibiting transient ossification during maturation of the axis) may
appear as a fracture of the dens, though is a vertebral remnant in extinct reptiles.
Thoracic vertebrae
- 13
- Mammillary processes
 Projections on transverse processes for muscular attachment
 Begin at T2 or T3
- Accessory processes
 Last few thoracic vertebrae
 Caudally-directed projections arising from the pedicles
 Near intervertebral foramen and may cause spinal nerve compression if overgrown
Cranial/Caudal costal fovea
 Demifacets for heads of ribs
- “Anticlinal vertebra” (T11)
 Name derived from its vertical spinous process, whereas the T 12 and T13 that follow have craniallydirected spines
 3 distinct features
o Vertical spinous process
o 1st vertebra to lose intercapital ligament and exhibit complete fovea for the rib
o Cranial articular facet begins to present itself at base of the mammillary process (continuous
though lumbar vertebrae)
Lumbar vertebrae
- 7
- Broad spinous processes
- Cranially-directed transverse processes
- Prominent mammillary processes
- Accessory processes gradually dimish in size and may be absent in last 2 vertebrae
- Cranial/caudal articular facets
 Lie in sagittal plane, limiting lateral flexion and maximizing dorsoventral flexion and extension
Sacrum
- Fusion of 3 sacral vertebrae
- No intervertebral discs
- Median sacral crest
 Fused spinous processes
- Intermediate sacral crest
 Fused mammilloarticular processes
- Lateral sacral crest
 Fused transverse processes
- Wings of the sacrum
 Enlarged, cranial parts of the sacrum
 Exhibit articular facets for ilial articulation
- Base
 Cranial part of sacrum
- Apex
 Caudal part of sacrum
- Dorsal surface
 2 pairs of dorsal sacral foramina (smaller)
- Ventral surface
 2 pairs of pelvic sacral foramina (larger)
Caudal vertebrae
- Variable in number (~20)
- Hemal arches
 On 4th, 5th, 6th vertebrae
 Separate bones that articulate with ventral surfaces of these vertebrae
 Median coccygeal artery travels caudally within hemal arches
- Hemal processes
 On 6th – 17th vertebrae
Ribs
- 13 pairs (dogs and cats)
- Sternal ribs
 First 9 rib pairs
 Articulate with sternum directly
- Asternal ribs
 Last 4 rib pairs
 Indirectly connected to the sternum by the costal arch
- Floating ribs
 Last rib pair
 Costal cartilages are not attached to the costal arch
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Rib anatomy
 Vertebral extremity
o Head (articulates with costal fovea on vertebral bodies)
o Neck
o Tubercle (exhibits facet that articulates with transverse process of same-numbered vertebra)
o Costotransverse foramen (space between head and tubercle as it articulates with vertebra)
 Sternal extremity
 Costal groove
o On caudal border of each rib
o Deep groove for intercostal vessels (artery/vein) and nerve
Sternum
- Made up of 8 individual bones called sternebrae
- Forms floor of thorax
- Intersternal cartilage
 Fibro-cartilage discs that connect all sternebrae
 All costal cartilages (except from 1st rib pair) articulate here
- Manubrium
 1st stenebra
 Articulates with costal cartilages of 1st rib pair
- Xiphoid process
 Last sternebra
 Extends caudally by xiphoid cartilage
Brachial Plexus
- Formed by primary ventral branches of C 6, C7, C8, T1, T2
- Suprascapular n.
 Larger nerve that enters the space between the supraspinatus and subscapularis muscles and runs along
the neck of the scapula
 Supplies the supraspinatus and infraspinatus muscles
 Damage to this nerve may result in a prominent scapular spine due to muscle atrophy or an abducted
shoulder, where the muscle atrophy would account for joint instability
- Subscapular n.
 Innervates the subscapularis m.
 Clinically unimportant (damage to this nerve does not result in dysfunction because the subscapularis m.
is also innervated by the axillary n.)
- Axillary n.
 Enters the “axillary space” between the subscapularis and teres major muscles and emerges on the lateral
aspect
 Supplies the subscapularis and teres major muscles on the medial aspect of the scapula and the teres
minor and deltoid muscles on the lateral aspect
 Damage to this nerve does not result in any overt gait defects, though exhibits a prominent acromial
process
 Continuation of axillary n. is the cranial lateral cutaneous brachial n.
o Supplies a small AZ on the lateral aspect of the brachium
o Associated with the axillobrachial vein
o Continues on the antebrachium where it is called the cranial cutaneous antebrachial n. It is here
on the antebrachium that the radial n. overlaps with innervation of the cutaneous branch of the
axillary n.
- Thoracodorsal n.
 Enters the latissimus dorsi m.
 Loss of this nerve is not clinically significant
- Caudal pectoral nerves
 Supply the superficial pectoral muscles
- Cranial pectoral nerves
 Supplies deep pectoral m.
- Nerve of the brachiocephalicus m.
 Sits on the deep surface of the coracobrachialis m.
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Small AZ along the cranial aspect of the brachium
Loss of this nerve is not clinically significant (because the brachiocephalicus m. is supplied by many
nerves)
Radial n.
 Largest nerve of the brachial plexus
 Enters the triceps m. between the long and medial heads, runs in the brachialis groove, emerges on the
lateral aspect of the brachium
 Supplies triceps m. (all heads) and tensor fascia antebrachii m.
 Branching occurs at the level of the shoulder joint
o Superficial branch (2 divisions lie on either side of the cephalic vein, prone to damage during an
improper venipuncture)
 Medial branch (digits 1 and 2)
 Lateral branch (digits 3-5)
o Deep branch
 Motor function to the extensor muscles
- Ulnaris lateralis m.
- CDE m.
- LDE .
- Abductor pollicis longus m.
- Supinator m.
- Tensor fascia antebrachii m.
- Anconeus m.
- Triceps m.
- Extensor carpi radialis m.
 Damage to the radial n. at the level of the shoulder joint prevents the animal from bearing weight
 Damage to the median branch of the radial n. is indicated by the animal chewing skin over digits 1 and 2
 Damage to the lateral branch of the radial n. is indicated by the animal chewing skin over digits 3-5
 Damage to the deep branch of the radial n. results in inability to extend the carpus or digits, which will be
knuckled
Ulnar n.
 Runs along the medial head of the triceps m. and the medial aspect of the olecranon process (“funny
bone”)
 Gives off a long caudal cutaneous antebrachial n.
o Supplies AZ on the caudal antebrachium
 Dorsal branch
o Runs to the abaxial surface of the fifth digit
 Palmar branch
o Overlaps with median n. on palmar aspect of digits
 Supplies 4 muscles
o DDF m. (humeral head)
o DDF m. (ulnar head)
o Flexor carpi ulnaris m.
o Interosseus m.
 Damage to ulnar n. causes no obvious gait defects, as the median n. can compensate for carpal and digital
flexion
 Damage to the ulnar n. will result in cutaneous deficit on the caudal antebrachium (AZ)
Median n.
 Supplies 6 muscles
o Pronator teres m.
o Pronator quadratus m.
o Flexor carpi radialis m.
o SDF m.
o DDF m. (radial head)
o DDF m. (humeral head)
 Loss of median n. may not cause any gait deficits because of overlap from ulnar n., which can
compensate for carpal and digital flexion
Musculocutaneous n.
 Proximal muscular branches
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o Biceps brachii m.
o Coracobrachialis m.
 Communicating branch to median n.
 Distal muscular branch
o Brachialis m.
 Medial cutaneous antebrachial n.
o Supplies AZ
 Damage to the musculocutaneous n. may result in extremely weak flexion of the elbow
 Definitive diagnosis of damage is demonstrated by lack of sensation on medial antebrachium
Lateral thoracic n.
 Innervated cutaneous trunci m.
Long thoracic n.
 Innervated serratus ventralis m.
Vasculature of the Thoracic Limb
- Axillary artery
- Superficial cervical artery (find it in relation to the superficial cervical lymph node)
- Subscapular artery
 Thoracodorsal artery
 Caudal circumflex humeral artery
- Brachial artery
- Transverse cubital artery
- Common interosseus artery
- Cephalic vein
- Median cubital vein
- Axillobrachial vein
Lumbosacral plexus
- All nerves of the pelvic limb are derived from ventral branches of the spinal nerves
- Sciatic n.
 Largest nerve in the body
 Has spinal contributions from L6-S1/S2
 Supplies 6 muscles
o Gemelli m.
o Internal obturator m.
o Quadratus femoris m.
o Biceps femoris m.
o Semitendinosus m.
o Semimembranosus m.
 Terminal branches of sciatic n. (given off at level of lower 3 rd of femur)
o Tibial n.
o Common peroneal n.
 Cutaneous branches
o Caudal cutaneous sural n.
o Lateral cutaneous sural n.
 Damage to the sciatic n. can results from intramuscular injections, mid-shaft femoral fractures,
lacerations to the stifle, lumbo-sacral junction disc herniation, and fractures of the hipbone
 In damage to the sciatic n. at the level of the hip joint, the animals may still be able to exhibit weak
extension of hip joint (due to gracilis m., innervated by the obturator n.)
- Common peroneal n.
 Branches
o Superficial peroneal n.
o Deep peroneal n.
 Supplies 5 muscles
o Cranial tibial m.
o Long digital extensor m.
o Lateral digital extensor m.
o Peroneus longus m.
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o Peroneus brevis m.
 Damage to the common peroneal n. may result in inability to flex the hock or extend the digits
Tibial n.
 Runs into the popliteal space (space between the two heads of the gastrocnemius m.)
 Branches
o Medial plantar n.
o Lateral plantar n.
 Supplies 4 muscles
o Gastrocnemius m.
o SDF m.
o DDF m.
o Popliteus m.
 Damage to the tibial n. exhibits exactly opposite to common peroneal n. damage. The animal will show
weak extension of the hock, a total inability to flex the digits, and sensory deficits in the plantar aspect of
the pes. Animal is able to weakly extend hock because of the action of muscles innervated by sciatic
(semitendinosus m., biceps femoris m.) and obturator (gracilis m.) nerves
Femoral n.
 Originates from L5, with contributions from L4 and L6 (same as obturator n.)
 Main continuation is saphenous n.
o AZ on medial aspect of stifle region
o Supplies skin all the way to the abaxial aspect of the 2nd digit
 Damage to femoral n. results in loss of patellar reflex, inability to extend stifle, weak hip flexion
Gluteal n.
 Cranial gluteal n.
o Middle gluteas m.
o Deep gluteus m.
o Tensor fascia latae m.
 Caudal gluteal n.
o Superficial gluteus m.
o Middle gluteus m.
o Piriformis m.
 Fairly unimportant from clinical perspective
Obturator n.
 Main nerve is in pelvic cavity and runs through the obturator foramen
 Originates from L5, with contributions from L4 and L6 (same as femoral n.)
 Terminates in 4 muscles
o Pectineus m.
o Adductor m.
o External obturator m.
o Gracilis m.
 Damage results in inability to adduct affected limb, especially when on a smooth/slippery surface
Vasculature of Pelvic Limb
- Femoral triangle
 Defines the space between the sartorius (cranially), pectineus and gracilis (caudally), and vastus medialis
(laterally) muscles
 Occupied by 4 structures
o Saphenous n.
o Femoral artery
o Femoral vein
o Efferent lymphatics from popliteal lymph node
- Dorsal pedal artery
 Accompanied by the deep peroneal n.
 Artery is used for taking arterial blood sampling, blood pressure, and arterial pulse
- Superficial plantar venous arch
 On the plantar aspect of the digits
 Prone to cuts