Canine Hindlimb Anatomy

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Introduction

The hindlimb skeleton of the canine includes the pelvic girdle, consisting of the fused ilium, ischium, and pubis, and the bones of the hindlimb. The bones of the hindlimb are femur, patella, fabella, tibia, fibula, tarsus and meta-tarsus. The size of hindlimb bones varies due to the significant variation in size for breeds of dogs.

Osteology of Pelvic Limb

The Pelvic limb bears 40-45% of the weight and provides the majority of the propulsion for locomotion.

Os coxae

• Tuber coxae end tubes sacrale both palpable
• Tuber ischii underneath hamstrings

Femur

• Heaviest and largest canine bone
• Has a relatively thick and short femoral neck with relatively short and wide shaft with a narrow isthmus in the middle
• Greater trochanter lateral to the head of the humerus
• Lesser trochanter distal to head of humerus
• Trochanteric fossa: Caudal depression  between  the  trochanters
• Third trochanter: Lateral aspect distal to greater trochanter
• Extensor fossa: depression on lat condyle for insertion of long digital extensor.
• Femoral trochlea: Groove on cran femur for articulating with patella bound by two ridges of which the medial is thicker.

Patella

• The canine patella, or kneecap, is the largest sesamoid bone in the body.
• It is an ossification in the quadriceps femoris muscle.
• The patella alters the pull, increases the moment arm, and protects the quadriceps tendon, and provides a greater contact surface for the tendon on the trochlea of the femur than would exist without the patella. The canine patellar articular surface is mildly convex

Fabellae

• Two small sesamoid bones embedded in the heads of the gastrocnemius muscle

1. Sesamoid in the lateral head is the largest, is palpable, and articulates with the lateral femoral condyle,
2. Sesamoid in the medial head is smaller and may not have a distinct facet on the medial femoral condyle.

Tibia

• Major bone in the crus.
• Proximal tibia is wider than the distal cylindrical tibia.
• Medial and lateral tibial condyles, an intercondylar eminence, and a tibial tuberosity are on the proximal tibia.
• Large tibial tuberosity  -  patellar ligament
• Tibial plateau slopes distally from cranial to caudal. The extensor groove, on the cranial tibia and lateral to the tibial tuberosity, provides a pathway for the long digital extensor muscle. There is a popliteal notch on the caudal tibia in the midline, where the popliteal vessels course.
• Tibia articulates with the fibula proximally, along the interosseous crest, and distally.
• The tibial cochlea articulate with the trochlea of the talus to form the talocrural joint.
• Cochlea = two grooves separated by a ridge.

Fibula

• Does not bear much weight.
• Is a long, slender bone that articulates with the tibia and also serves as a site for muscle attachment.
• A distinctive groove exists in the lateral malleolus, the sulcus malleolaris lateralis, through which course the tendons of the lateral digital extensor and peroneus brevis muscles.

Tarsals and metatarsals

• Dogs and cats have 7 tarsal bones
• Tarsus, or hock, consists of the talus, calcaneus, a central tarsal bone, and tarsal bones I to IV.
• Talus articulates with the distal tibia and has prominent ridges. At the talocrural joint, two convex ridges of the trochlea of the talus articulate with two reciprocal concave grooves of the cochlea of the tibia.
• Orientation of the grooves and ridges deviates laterally approximately 25 degrees from the sagittal plane. This deviation allows the hindpaws to pass lateral to the forepaws when dogs gallop.
• Calcaneus is large and serves as the insertion of the common calcaneal tendon.
• Central tarsal bone lies between the talus and the numbered tarsal bones I to III.
• Tarsal IV is large and articulates with the calcaneus and metatarsal bones, spanning this entire region.
• Hindpaw has five metatarsal bone
• Reduced first MT and digit (dew claw) often absent

Joints of the pelvic limb

Sacro-iliac

Type:

• Synchondrosis ( synovial joint - sacropelvic surface of ilium
• Joint capsule present

ROM:

• Minimal Designed for stability
• Accessory movements =  rotations

Supporting structures:

• Dorsal and ventral Sacroiliac ligaments
• Sacrotuberous

Hip

Type:

• Ball and socket
• Femoral head and acetabulum of the ilium, ischium and pubis
• A band of fibrocartilage on the rim of the acetabulum deepens acetabulium

ROM:

• Flexion & Extension
• Minimal - adduction & abduction

Supporting structures:

• Acetabular lip (fibrocartilage) continues as transverse ligament
• Ligament of the femoral head
• Synovial structures and tendon sheaths:

• Large joint capsule
• Internal obturator

Stifle

Type:

• Hinge joint with  two cartilages/menisci
• Femur & tibia - femorotibial (condylar)
• Femur & patella – femoropatellar (gliding joint)

ROM:

• Flexion and Extension
• At the end of flexion there is int rot
• At the end of extension there is external rotation

Supporting structures:

• Patellar ligament (patella is a sesamoid within the quadriceps  tendon)  
• Medial collateral ligament fused with joint capsule and med meniscus
• Lateral collateral ligament: Separated from lateral meniscus by popliteus tendon
• Cranial cruciate ligament: Caudolateral femur to cranial tibial. Prevents anterior translation of tibial relative to femur
• Caudal cruciate ligament: Craniomedial femur to caudal tibia. Prevents caudal translation of tibial relative to femur
• Lateral meniscus has extra ligament— meniscofemoral ligament
  1. Connects caudal lateral meniscus to femur
  2. Femoropatellar ligaments – lateral and medial
  3. Extend from epicondyles to patella

Hock (tarsal)

Type:

• Tarsocrural joint (TCJ)- greatest movement
• Proximal &  distal intertarsal  joint
• Tarsometatarsal joint
• Intertarsal

ROM:

• TCJ - Flexion & Extension and Lateral & rotatory accessory movement
• Others - small amount or translatory and rotatory ROM

Ligaments of the tarsal joint:

• Medial & lateral collateral (both have long and short parts)
• Intertarsal ligaments
• Proximal extensor retinaculum
• Transverse ligament on distal tibia
• Holds down tendons of long digital extensor and cranial tibial
• Distal extensor retinaculum
• Hold down tendon of long digital extensor
• Long plantar ligament - connect calcaneus to metatarsus
• Flexor retinaculum - thickening of deep fascia over plantar aspect of tarsus
• Form the tarsal canal  with  the tarsal bones containing:
  • Tendon and sheath of Deep digital flexor
  • Plantar branch of saphenous artery & vein
  • Medial & Lateral plantar nerves

Muscles of the Hind Limb

Muscles of the Hip

Muscle	Origin	Insertion	Action	Nerve Supply
Pectineus	Pubis	Femur	Adduct the limb and flexes the hip	Obturator
Iliopsoas Iliacus Psoas	Ventral surface of lumbar vertebrae Ventral surface of the wing of Ilium	Lesser of trochanter of Femur	Flexes Hip and externally rotates the thigh	Ventral branches of Lumbar Spinal Nerves
Gracilis	Pubis Symphysis	Medial Tibia	Adduct limb	Obturator
Adductors	Pubic surface limb symphysis		Adduct limb	Obturator
Internal Obturator	Pelvic floor	Trochanteric fossa of the femur	Lateral rotation of femur	Ischiatic nerve
Gemelli	Ischium	Trochanteric fossa of the femur	Lateral rotation of femur	Ischiatic nerve
External Obturator	Ventral Surface of pubis Ischium	Trochanteric fossa of the femur	Adduct thigh	Ischiatic
Quadratus femoris	Ischium	Caudal surface of femur	Extenf hip and adduct thigh	Obturator
Deep Gluteal	Body of ischium	On or near greater trochanter	Extension Abduction	Gluteal

Muscles of the Hip and Stifle 1

Muscle	Origin	Insertion	Action	Nerve Supply
Superficial gluteal	Dorsal to hip joint	Third trochanter	Abduct hip	Gluteal
Tensore fascia lata	Tuber coxae	Lateral femoral fascia	Hip flexion and stifle extension via tension on the lateral femoral fascia	Gluteal
Biceps femoris	Ischiatic tuberosity	Greater trochanter	Extend and Abduct hip	Gluteal
Semitendinosus	Ischiatic tuberosity	Tibia and calcaneal tub	Extend hip, flex stifle, extend tarsus	Ischiatic
Semimembranosus	Ischiatic tuberosity	Femur and Tibia	Extends hip, Flexes or extends stifle	Ischiatic

Muscles of the Hip and Stifle 2

Muscles	Origin	Insertion	Action	Nerve supply
Middle gluteal	Wing of ilium	Greater trochanter	Extension and abduction	Gluteal
Rectus femoris	Ilium (cranioventral iliac spine)	Patella and patellar tuberosity	Flexes the hip and extends the stifle	Femoral
Vastus lateralis	Proximal femur	Patella and patellar tuberosity	Extends the stifle	Femoral
Vastus medialis	Proximal femur	Patella and patellar tuberosity	Extends	Femoral
Vastus intermedius	Proximal femur	Patella and patellar tuberosity	Extends	Femoral

Muscles of the Stifle, Hock and Pes

Muscles	Origin	Insertion	Action	Nerve Supply
Gastrocnemius	Distocaudal surface of the femur	Calcaneal tuberosity	Extends tarsus and flexes stifle	Tibial
Long digital extensors	Extensor fossa of femur	extensor processes of distal phalanges	Flexes hip and extends stifle	Peroneal
Soleus	Head of fibula	Tendon and lateral head of gastrocnemius	Extends tarsus	Tibial
Lateral digital extensor	Fibula	Lateral aspect of digit	Extend digit and flexes tarsus	Peroneal
Deep digital flexor	Tibia and fibula	Distal phalanges	Extends tarsus and flexes digit	Tibial
Superficial digital flexor	Caudal distal femur, deep to gastrocnemius	Calcaneal tuberosity and middle phalanx	Flexes stifle, extends tarsus and flexes digit	Tibial

Nerves of the Pelvic Limb

Femoral nerve (L4, L5 sometimes L3, L6)

• Muscle Innervation - Stifle extensors (quadriceps), llio-psoas.
• Cutaneous Innervation - Medial aspect of limb

Obturator nerve (L5, L6)

• Muscle Innervation - Adductors - obturator, add, gracilis
• Cutaneous Innervation - nil

Gluteal nerve (L6, L7, S1)

•  Muscle Innervation - Gluteals, TFL, Biceps femoris, Semitendinosus.
• Cutaneous Innervation - nil

Sciatic nerve (L6, L7, S1, S2)

• Muscle Innervation - Biceps Femoris, semitendinosus, semimembranosus
• Cutaneous Innervation - see tibial and fibula branches

Tibial nerve (S1, S2)

• Muscle Innervation - extensors of hock, flexors of digits
• Cutaneous Innervation - caudal aspects of the limb below stifle

Fibular nerve

• Muscle Innervation - flexors of the hock, extensors of the digits    
• Cutaneous Innervation - cranial and lateral aspects of limb