Lecture 7 -- Equine Proximal Limb Hindlimb Anatomy

What is a key difference in the ilium between horses and dogs?

The wing of the ilium has a horizontal orientation in horses, unlike the vertical orientation in dogs.

Which parts of the pelvis are more difficult to palpate in horses compared to dogs?

Tuber sacrale (Covered by gluteal muscles) + Tuber ischium (Covered by hamstring muscle)

How many sacral vertebrae are fused to form the sacrum in horses?

5

What type of joint is the sacroiliac joint? Is any movement allowed within it?

Cartilaginous joint + Synovial joint → Minimal movement is allowed

Unlike dogs, the sacrotuberous ligament in horses is much broader and divided into two parts. What are they? Where do these two ligaments originate?

1. Dorsal sacroiliac ligament

2. Ventral sacroiliac ligament

Origin: Dorsal sacrum + C1

During parturition, what happens with the broad ligament and sacrum?

Influenced by hormone during parturition, the sacrum is soften + relax sacrotuberous ligament → More flexibility of expansion of pelvis

There are two holes created by the dorsal sacroiliac ligament and ventral sacroiliac ligament. What are they called? What passes through the lesser ischiatic foramen?

1. Greater ischiatic foramen

   → Located above the greater ischiatic notch

   → Gluteal nerve pass through

2. Lesser ischiatic foramen

   → Located above the lesser ischiatic notch

   → Sciatic nerve pass through

Which muscles originate from the sacrotuberous ligament?

1. Biceps femoris

2. Superficial gluteal

3. Piriformis

4. Tenuissimus

What is a key feature of the head of the equine femur?

The large fovea on the head of the femur → Allow the attachment for round ligament + accessory ligament

What is the accessory ligament of the hip joint?

A continuation of the prepubic tendon that runs from the pecten under the transverse ligament

What are the differences between the hamstring muscles in horses and dogs?

Extra origin in horses: Lumbosacral fasica

What is the name of the rump in horses?

Rounded rump = Croup

What is the function of the gluteal muscles in the hindlimb?

Limb retraction and hip extension

NO abduction

Why dislocation of femur is uncommon in horses?

Horses have two ligaments (Round ligament and accessory ligament) → More stability

What are the main features of the proximal end of the equine femur?

→ Greater trochanter is divided into two parts: Cranial and caudal

→ Third trochanter in lateral aspect

What is the function of third trochanter?

Allow insertion of superficial gluteal muscle

Unlike dogs, how many ligaments do horses have?

3

Medial, middle and lateral

Where does the lateral and medial femora-patellar ligament originate and attach to?

Patella to femoral epicondyle

!! The ligament does not extend to the caudal aspect because horses do not have fabellar !!

What is the function of the femoro-patellar ligaments?

Holds patella on vertical / gliding surface.

What are the differences between the sesamoid bones in the stifle joint of horses and dogs?

No popliteal and fabellae

Describe the patellar locking mechanism.

The stifle is extended, the patella rotates medially → Medial patellar ligament hooks over the medial trochlear ridge → Locks the stifle in extension + Allow other hindlimb to rest

What is “locked” patella

Have difficulty in unlocking the patella → Need to cut medial straight patellar ligament → Allow to release some tension BUT the horse may loss the ability to lock the patellar

How many components do the joint capsule of stifle joint form?

3

1. Femoro-patellar

2. Lateral femoro-tibial

3. Medial femoro-tibial

What are the differences between those compartment in stifle joint in horses, compared to dogs?

Dogs: Three compartment have NO communication

Horses: Meidal femoro-tibial and lateral femora-tibial compartments have no communication BUT lateral femoro-tibial and femoro-patellar has 25% communication + medial femoro-tibial and femoro-patellar has most communication

Describe the equine fibula.

1. Reduced in size

2. Fuses halfway down the tibia → The lateral malleolus is part of the tibia as tibia and fibula fuse together BUT in dogs, the lateral malleolus is part of the fibula

What are the palpable landmarks of the equine hindlimb?

1. Greater trochanter

2. Third trochanter

3. Lateral & medial condyles

4. Tibial tuberosity

5. Patella

6. Medial & lateral malleoli