Equine Proximal Hindlimb

Page 1: Overview of Equine Proximal Limb

  • Focus on functional anatomy of the equine proximal limb

  • Key areas of study:

    • Regions & Bones

    • Differences in:

      • Pelvis

      • Hip Joint

      • Femur & Stifle joint

      • Tibia & Fibula

Page 2: Learning Outcomes

  1. Describe the surface anatomy and skeletal/muscular anatomy of the equine hindlimb and proximal limb.

  2. Describe the joints of the equine hindlimb and their movements.

  3. Identify supportive and synovial structures of the hindlimb and describe the patellar locking mechanism.

Page 3: Hindlimb Regions & Bones

  • Predominantly similar to dog anatomy.

  • Distal to tarsus:

    • Similar to forelimb in structure.

    • 3rd digit as weight-bearing component.

  • Anatomical distinctions:

    • Forelimbs: Main weight bearers.

    • Hindlimbs: Primarily for propulsion.

    • Clinical significance: Important in disciplines like dressage.

  • Key components:

    • Hip

    • Pelvis

    • Thigh

    • Femur

    • Patella

    • Stifle

    • Crus

    • Tibia & Fibula

    • Hock or tarsus

    • Pes

    • Metatarsus

    • Digit

Page 4: Pelvis Anatomy

  • Components of Pelvis:

    • Ilium

    • Ischium

    • Pubis

    • Acetabulum

  • Lateral view features:

    • Tuber Sacral (highest point)

    • Wing of ilium

  • Dorsal view features:

    • Tuber coxae

    • Tuber ischium

  • Orientation of wing of ilium:

    • Horizontal in horses, vertical in dogs.

Page 5: Palpable Features of Pelvis

  • Notable palpable landmarks:

    • Tuber Sacrale (difficult to palpate)

    • Tuber Coxae (palpable)

    • Tuber Ischium (requires deep palpation)

Page 6: Sacroiliac Joint

  • Anatomy:

    • Composed of 5 fused sacral vertebrae in horses (compared to 3 in dogs).

    • Location: Between lateral sacrum and medial aspect of ilium wings.

  • Joint type: Partly cartilaginous, partly synovial with small capsule.

  • Movement capabilities: Limited.

  • Functionality: Transfers forces during locomotion; softens during parturition.

Page 7: Sacrotuberous & Broad Ligament

  • Description: Strong fibrous ligaments from dorsal sacrum and first coccygeal vertebra to ischiatic tuberosity.

  • Forms lateral wall of pelvic cavity.

  • Types:

    • Dorsal sacroiliac ligament (DSL)

    • Ventral/lateral sacroiliac ligament (VSL)

  • Clinical significance: Both relax at parturition.

Page 8: Nerve Pathways and Muscle Origins

  • Greater ischiatic foramen: Contains the gluteal nerve.

  • Lesser ischiatic foramen: Contains the sciatic nerve and is associated with certain muscle origins (biceps femoris, superficial gluteal, piriformis, tenuissimus).

  • Notable absence of the structure in cats.

Page 9: Hip Joint Anatomy

  • Key components of acetabulum:

    • Lunate surface

    • Acetabular fossa (deep)

    • Transverse ligament

  • Femoral head features: Large fovea for ligament attachments.

Page 10: Accessory Ligament of Hip Joint

  • Continuation of the prepubic tendon.

  • Anatomy: Runs from pecten and grooves in ventral pubis under transverse ligament.

  • Functional role: Provides tension due to weight of abdominal contents.

Page 11: Hindlimb Retractor Muscles

  • Major muscles:

    • Biceps femoris

    • Semitendinosus

    • Semimembranosus

  • Originates from ischium and lumbosacral fascia.

  • Notable characteristics: Rounded rump, referred to as "croup."

Page 12: Gluteal Muscles Function

  • Well-developed in horses.

  • Originates from sacrum and pelvis, inserts at greater trochanter.

  • Functions primarily in limb retraction and hip extension.

  • Abduction not possible in horse's hindlimb due to anatomical differences.

Page 13: Vertebral Column & Propulsion

  • Features a relatively rigid vertebral column.

  • Powerful hindlimb retractor/hip extensor muscles facilitate propulsion.

  • Dynamics allow horse to perform galloping, rearing, bucking/kicking, and jumping actions.

Page 14: Hip Movement Dynamics

  • Hip movement constrained by ligaments and muscle mass.

  • Notable limitation: Only flexion & extension allowed, no abduction (unlike dogs).

  • Dislocations are rare and largely disastrous.

Page 15: Femur Anatomy (Proximal End)

  • Key features:

    • Greater trochanter (2 parts)

    • Lesser trochanter

    • Third trochanter (lateral aspect, also known as trochanter tertius)

  • Anatomical landmarks:

    • Neck

    • Head of femur (fovea)

    • Various condyles (medial/lateral) and epicondyles.

Page 16: Femur Anatomy (Distal End)

  • Features:

    • Medial & lateral condyles

    • Medial trochlear ridge larger than lateral.

    • Trochlear groove divided into parts for different articular surfaces.

Page 17: Patella and Associated Components

  • Features:

    • Large medial projection and extensive parapatellar cartilage that forms a medial hook.

    • Associated muscles include Quadriceps and Sartorius.

    • Presence of 3 patellar ligaments:

      • Medial

      • Middle

      • Lateral

  • Notable absence of fabellae and popliteal sesamoid.

Page 18: Stifle Joint Anatomy

  • Femorotibial similar to dog anatomy.

  • Unique elements:

    • Lateral and medial femoro-patellar ligaments to stabilize stifle joint against dislocation.

Page 19: Patellar Locking Mechanism

  • Mechanism:

    • Upon stifle extension, patella moves proximally and rotates medially.

    • Engages horizontal/resting surface locking the joint in extension.

    • Patella must then move back to midline to unlock.

  • Critical for 'stay apparatus' to lock leg and allow rest.

Page 20: Clinical Significance of Patellar Locking

  • 'Locked' patella could improve muscle strength issues.

  • Surgical interventions like cutting the medial straight patellar ligament may be necessary.

Page 21: Stifle Joint Compartmentalization

  • Joint capsule divided into 3 main compartments:

    • Femoropatellar (FP)

    • Lateral femorotibial (LFT)

    • Medial femorotibial (MFT)

  • Communication characteristics among compartments:

    • LFT & FP: 25% communication.

    • MFT & FP: Most horses show communication.

Page 22: Tibia & Fibula Overview

  • Tibia: Weight-bearing bone with a medial malleolus.

  • Fibula: Reduced size, fused half-way down the tibia, with a distal lateral malleolus.

Page 23: Palpable Landmarks of Hindlimb

  • Notable landmarks for assessment:

    • Greater trochanter

    • Third trochanter

    • Lateral & medial condyles

    • Tibial tuberosity

    • Patella

    • Medial & lateral malleoli

  • Assessments should consider both flexion & extension.