Lower Limb Anatomy: Hip, Pelvis, and Thigh

Bones of the Lower Limb

  • Overview

    • The lower limb consists of the pelvic girdle and the free lower limb.
    • Pelvic Girdle: Includes the hip bone (1/2 of the pelvic girdle), iliac crest, lumbar vertebrae, sacrum, coccyx, bony pelvis, pubic symphysis, and ischiopubic ramus.
    • Free Lower Limb: Includes the thigh (femoral region), patella, knee region, knee joint, leg region, tibia, fibula, ankle region, lateral and medial malleoli, ankle joint, tarsus, foot region, metatarsus, and phalanges.

Bones of the Hip Joint

  • Os Coxa: Consists of the ilium, ischium, and pubis.

  • Acetabulum: Includes the acetabular notch, acetabular fossa, and lunate surface.

Bones of the Proximal Lower Limb

  • Femur: Key features include:

    • Head
    • Neck
    • Lesser trochanter
    • Greater trochanter
    • Intertrochanteric line
    • Femoral condyles
    • Patellar surface
    • Lateral epicondyle
    • Medial epicondyle
    • Adductor tubercle
    • Intertrochanteric crest
    • Trochanteric fossa
    • Linea aspera
    • Gluteal tuberosity
    • Spiral line
    • Pectineal line
    • Intercondylar fossa

  • Patella: The largest sesamoid bone.

Body Weight and the Lower Limb

  • Weight-bearing forces are concentrated at the condyles.

Fascia of the Lower Limb

  • Thigh

    • Superficial fascia
    • Deep fascia: Includes the fascia lata and iliotibial tract (IT band).

  • Compartments

    • Anterior
    • Medial
    • Posterior

  • The iliotibial (IT) band is a thickening of the fascia lata.

Venous Drainage of the Lower Limb

  • Superficial Veins
    • Great saphenous vein: Originates from the dorsal venous arch.
    • Accessory saphenous veins
    • Lateral and anterior cutaneous veins
    • Small saphenous vein
  • Perforating Veins: Connect superficial and deep veins.
  • Deep Veins
    • Venae comitantes: Two small veins accompanying arteries.
    • Potential site for deep vein thrombosis (DVT).

Varicose Veins

  • Venous stasis and ulceration can occur.
    Tissues breakdown, issues can't fight infections

Deep Vein Thrombosis (DVT) and Pulmonary Embolism

  • A clot (embolus) can travel from the leg to the lung.

Lymphatic Drainage of the Lower Limb

  • Lymphatic drainage tends to follow the veins.
  • Enters the lumbar lymphatic trunk, then the chyle cistern.
  • Flows to the thoracic duct and left venous angle.

Lower Limb Lymphedema

  • Occurs when lymphatic vessels and nodes are not functioning, impairing lymphatic drainage.
  • Different from deep vein thrombosis, which is a blood clot.

Dermatomes of the Lower Limb

  • L1: Inguinal region
  • L2: Medial thigh
  • L3: Medial knee
  • L4: Medial malleolus
  • L5: Lateral leg
  • S1: Lateral foot
  • S2: Medial heel
  • S3-S5: "Saddle" sensation

Cutaneous Innervation of the Lower Limb

  • Gluteal Region

    • Cutaneous branches of dorsal rami L1-L3 and sacral rami S1-S3
    • Lateral cutaneous branch of the iliohypogastric nerve
    • Lateral femoral cutaneous nerve, posterior branch

  • Posterior Thigh

    • Posterior femoral cutaneous nerve
    • Cutaneous branch of the obturator nerve
    • Lateral femoral cutaneous nerve
    • Medial femoral cutaneous nerve

  • Leg

    • Saphenous nerve
    • Lateral sural cutaneous nerve
    • Medial sural cutaneous nerve

  • Sole of Foot

    • Medial calcanean branch of the tibial nerve
    • Dorsal lateral cutaneous nerve of the foot
    • Lateral plantar nerve
    • Medial plantar nerve

  • Tarsal Tunnel Syndrome

Anterior and Medial Thigh

  • Key Topics

    • Femoral triangle
    • Muscles of the anterior and medial thigh
    • Nerves and vessels of the anterior and medial thigh
    • Adductor canal and hiatus

Femoral Triangle

  • Boundaries

    • Inguinal ligament
    • Adductor longus
    • Sartorius

  • Femoral Sheath

    • Femoral artery
    • Femoral vein
    • Femoral canal (contains lymph nodes and vessels)

  • Floor

    • Iliopsoas
    • Pectineus

  • Contents

    • Femoral nerve
    • Femoral sheath
    • Femoral artery
    • Femoral vein

Anterior Thigh Muscles

  • Pectineus

    • Innervation: Femoral nerve (L2, L3)
    • Actions: Adduct, flex hip, and medially rotate hip

  • Iliopsoas

    • Chief hip flexor (discussed previously)

Anterior Thigh Muscles

  • Sartorius

    • Attachments: ASIS (Anterior Superior Iliac Spine) to the superior part of the medial condyle of the femur (Pes anserine insertion)
    • Innervation: Femoral nerve (L2, L3)
    • Actions: Flex, abduct, and externally rotate hip; flex knee (“tailor sitting” muscle)

  • Quadriceps Femoris

    • Attachments: Patellar tendon to tibial tuberosity
    • Rectus Femoris: AIIS (Anterior Inferior Iliac Spine)
    • Vastus Lateralis: Greater trochanter and lateral lip of linea aspera
    • Vastus Medialis: Intertrochanteric line and medial lip of linea aspera
    • Vastus Intermedius: Anterior and lateral surfaces of the body of the femur
    • Innervation: Femoral nerve (L2, L3, L4)
    • Actions: Extend knee joint; rectus femoris also flexes the hip joint

Medial Thigh Muscles

  • Adductor Longus

    • Innervation: Obturator nerve (L3)
    • Actions: Adduct hip

  • Adductor Brevis

    • Innervation: Obturator nerve (L3)
    • Actions: Adduct and weakly flex hip

Medial Thigh Muscles

  • Adductor Magnus

    • Innervation: Obturator nerve (L3) and tibial part of the sciatic nerve (L3, L4)
    • Actions: Adduct and flex/extend hip

  • Gracilis

    • Attachments: Body and inferior ramus of pubis to the superior part of the medial surface of the tibia (Pes anserine insertion)
    • Innervation: Obturator nerve (L2)
    • Actions: Adduct hip, medially rotate, and flex knee

Medial Thigh Muscles

  • Obturator Externus

    • Attachments: Margins of obturator foramen and obturator membrane to the trochanteric fossa of the femur
    • Innervation: Obturator nerve
    • Action: Laterally rotates hip

Nerve of the Anterior Thigh

  • Femoral Nerve

    • Largest branch of the lumbar plexus
    • Branches into the saphenous nerve

Nerve of the Medial Thigh

  • Obturator Nerve

    • Anterior branch: Supplies adductor longus and adductor brevis
    • Posterior branch: Supplies adductor magnus

Obturator Nerve Summary

  • Origin: Lumbar plexus (L2, L3, L4)
  • Motor Innervation: Obturator externus, adductor brevis, adductor longus, adductor portion of adductor magnus, and gracilis
  • Sensory Innervation: Medial thigh skin over adductors
  • Twig to Pectineus: Sometimes/rarely innervated by the obturator nerve.

The Lumbar Plexus Summary

  • Femoral Nerve

    • Muscular innervation of the anterior thigh: iliacus, sartorius, rectus femoris, vastus intermedius, vastus medialis, vastus lateralis, pectineus

  • Obturator Nerve

    • Muscular innervation: Obturator externus, adductor brevis, adductor longus, adductor magnus, gracilis
    • Cutaneous innervation of the medial thigh

Arteries of the Thigh

  • Femoral Artery

    • Deep artery of the thigh (profunda femoris)
    • Circumflex femoral arteries (medial and lateral)
    • Obturator artery

Adductor Canal/Hiatus

  • Adductor Canal

    • Deep to sartorius
    • Boundaries: Anteriorly and laterally by vastus medialis; posteriorly by adductors longus and magnus; medially by sartorius
    • Contents: Femoral artery, femoral vein, nerve to vastus medialis

  • Adductor Hiatus

    • The junction/window for the saphenous nerve behind the knee.
    • Saphenous nerve exits into the popliteal fossa.