Lower Limb Anatomy: Back of the Thigh

Introduction

• Topic: Back of the Thigh
• Also known as:
  • Posterior Compartment
  • Flexor Compartment
• Opposite of upper limb anatomy

Compartments of the Thigh

• Formed by deep fascia:
  • Anterior Compartment
  • Posterior Compartment
  • Medial Compartment

Cutaneous Innervation

• Supplied by branches from:
  • Posterior Cutaneous Nerve of the Thigh

Hamstring Muscles

• Collective name for muscles in the back of the thigh
• Muscles included:
  • Semitendinosus
  • Semimembranosus
  • Long head of Biceps Femoris
  • Ischial head of Adductor Magnus

Characteristics of Hamstring Muscles

1. Origin from ischial tuberosity
2. Insert into bones of the leg (tibia/fibula)
3. Supplied by the tibial part of the sciatic nerve
4. Function: Flex knee and extend hip

Importance of Hamstring Muscles

• Essential for walking and running
• Length varies among individuals, affecting flexibility

Muscle Attachments

• Semitendinosus:
  • Origin: Inferior medial impression on upper part of ischial tuberosity
  • Insertion: Upper part of medial surface of tibia
• Semimembranosus:
  • Origin: Superior lateral impression on upper part of ischial tuberosity
  • Insertion: Tibia
• Long Head of Biceps Femoris:
  • Origin: Ischial tuberosity (with semitendinosus)
  • Insertion: Fibula
• Adductor Magnus:
  • Largest muscle in the back of the thigh
  • Hybrid muscle (double nerve supply)
  • Functions: Adduct thigh and assist in flexing the knee

Sciatic Nerve

• Thickest nerve in the body
• Branches from sacral plexus (L4, L5, S1, S2, S3)
• Divided into:
  • Tibial Part
  • Common Peroneal Part

Course and Relations of Sciatic Nerve

• Enters back of thigh at lower border of gluteus maximus
• Relations:
  • Superficial: Long head of biceps
  • Deep: Adductor Magnus
  • Medial: Semimembranosus, Semitendinosus
  • Lateral: Biceps Femoris

Arterial Supply

• Supplied by terminal branches of profunda femoris artery
• Perforating branches (four in number) supply posterior compartment

Anastomosis

• Trochanteric Anastomosis:
  • Between gluteal arteries (internal iliac) and circumflex arteries (external iliac)
• Cruciate Anastomosis:
  • Between branches of medial/lateral circumflex and perforating branches of profunda femoris

Clinical Relevance

• Sciatica: Compression of sciatic nerve leading to pain
• Semimembranous bursitis: Inflammation of bursa
• Baker's cyst: Herniation of synovial membrane
• Injury to sciatic nerve: Muscle wasting and weakness