LOWER LIMB

LECTURE 1: PELVIC GIRDLE

The pelvic girdle is a crucial structure in the lower limb, consisting of various muscles that facilitate movement and stability. The highlighted points are essential for memorization, while the remaining content should be reviewed for comprehension.

Muscles of the Pelvic Girdle

Anatomical Overview:
- The anterior compartment includes:
  - Psoas major
  - Psoas minor
  - Iliacus
Iliopsoas Muscle:
- Composed of the psoas major and iliacus muscles.
- Attachments:
  - Proximal:
    - Psoas major: Sides of T12 to L5 vertebrae and intervertebral discs.
    - Psoas minor: Sides of T12 to L1 vertebrae.
    - Iliacus: Iliac crest, iliac fossa, ala of sacrum, anterior sacroiliac ligaments.
  - Distal:
    - Psoas major: Lesser trochanter of femur.
    - Psoas minor: Pectineal line, iliopectineal eminence.
    - Iliacus: Tendon of psoas major, lesser trochanter, femur distal to it.
- Innervation:
  - Psoas major: Ventral rami of lumbar nerves (L1, L2, L3).
  - Psoas minor: Ventral rami of lumbar nerves (L1, L2).
  - Iliacus: Femoral nerve (L2, L3).
- Main Action:
  - Chief flexor of the thigh; flexes the trunk on the hip when the thigh is fixed.
  - Acts as a postural muscle, preventing hyperextension of the hip joint during standing.

Gluteal Region

Anatomical Overview:
- Located posterior to the pelvis, between the iliac crests and the inferior borders of the gluteus maximus.
- Intergluteal cleft separates the buttocks; gluteal sulcus marks the boundary between buttock and thigh.
Gluteal Muscles:
- Composed of three large muscles primarily responsible for thigh extension and abduction:
  - Gluteus maximus
  - Gluteus medius
  - Gluteus minimus
- A deeper group of smaller muscles that serve as lateral rotators and stabilize the hip joint:
  - Piriformis
  - Obturator internus
  - Obturator externus
  - Gemelli (superior and inferior)
  - Quadratus femoris

Gluteus Maximus

Anatomical Features:
- Most superficial and largest gluteal muscle.
- Covers other gluteal muscles except the posterior third of gluteus medius.
- Forms a pad over the ischial tuberosity.
Attachments:
- Proximal:
  - Ilium (posterior to the posterior gluteal line).
  - Dorsal surface of sacrum and coccyx.
  - Sacrotuberous ligament.
- Distal:
  - Most fibers end in the iliotibial tract; some insert on the gluteal tuberosity of the femur.
Innervation:
- Inferior gluteal nerve (L5, S1, S2).
Actions:
- Extension and lateral rotation of the thigh at the hip joint.
- Adduction of the thigh.
- Active during forceful movements such as rising from a seated position or running.
- Stabilizes the knee via the iliotibial tract.

Iliotibial Tract

Deep fascia of the thigh known as fascia lata.
Lateral part thickened to form the iliotibial tract, a broad band of fibers.
Extends from the iliac tubercle to the lateral condyle of the tibia, crossing the knee joint.

Tensor of Fascia Lata

Attachments:
- Proximal:
  - Anterior superior iliac spine.
  - Anterior part of iliac crest.
- Distal:
  - Iliotibial tract.
Innervation:
- Superior gluteal nerve (L4, L5).
Actions:
- Abduction, medial rotation, and flexion of the thigh.
- Helps to keep the knee extended and stabilizes the trunk on the thigh.

Gluteus Medius and Minimus

Fan-shaped muscles with fibers running in the same direction.
Same actions, nerve, and arterial supply.
Attachments:
- Proximal:
  - Gluteus medius: External surface of ilium between anterior and posterior gluteal lines.
  - Gluteus minimus: External surface of ilium between anterior and inferior gluteal lines.
- Distal:
  - Gluteus medius: Lateral surface of greater trochanter.
  - Gluteus minimus: Anterior surface of greater trochanter.
Innervation:
- Superior gluteal nerve (L5, S1).
Actions:
- Abduction and medial rotation of the thigh.
- Essential for maintaining pelvic stability during locomotion.
- Prevents sagging of the unsupported side of the pelvis during walking.

Piriformis

Narrow, pear-shaped muscle located on the posterior wall of the lesser pelvis and posterior to the hip joint.
Attachments:
- Proximal:
  - Anterior surface of sacrum.
  - Sacrotuberous ligament.
- Distal:
  - Superior border of greater trochanter of femur.
Innervation:
- Branches of ventral rami of S1 and S2.
Key anatomical landmark in the gluteal region, influencing the naming of associated blood vessels and nerves.

Obturator Internus and Gemelli (Superior and Inferior)

These muscles form a tricipital (three-headed) muscle known as the triceps coxae.
Located between the piriformis and quadratus femoris muscles.
Obturator Internus:
- Partly located in the pelvis, covering most of the lateral wall.
- Attachments:
  - Proximal:
    - Pelvic surface of obturator membrane and surrounding bones.
  - Distal:
    - Leaves pelvis through the lesser sciatic foramen, attaching to the medial surface of the greater trochanter.
- Innervation:
  - With superior gemellus muscle (L5, S1).
Superior and Inferior Gemelli:
- Assist the obturator internus in its functions.

Muscles and Nerves of the Foot

Muscles of the Lateral Compartment of the Sole

Abductor digiti minimi:
- Function: Abducts and flexes the 5th digit (little toe).
Flexor digiti minimi brevis:
- Function: Flexes the proximal phalanx of the 5th digit.
Opponens digiti minimi:
- Function: Assists in the opposition of the 5th digit.

Muscles of the Central Compartment of the Sole

Flexor digitorum brevis:
- Function: Flexes the proximal phalanges of the 4 lateral digits (2nd to 5th).
Quadratus plantae:
- Function: Assists the flexor digitorum longus in flexing the lateral 4 digits (2nd to 5th).
Lumbricals:
- Function: Flexes proximal phalanges and extends middle and distal phalanges of the lateral 4 digits (2nd to 5th).
Plantar interossei:
- Function: Adducts digits 3 to 5 towards the 2nd digit and flexes metatarsophalangeal joints.
Dorsal interossei:
- Function: Abducts digits 2 to 4 away from the 2nd digit and flexes metatarsophalangeal joints.

Nerves of the Foot

Superficial Fibular Nerve:
- Supplies skin on the distal part of the anterior surface of the leg and nearly the dorsum of the foot.
Deep Fibular Nerve:
- Supplies skin on contiguous sides of the 1st and 2nd toes.
Tibial Nerve:
- Located posteroinferior to the medial malleolus, divides into the medial and lateral plantar nerves.
- Compression of the medial plantar nerve may occur during repetitive eversion of the foot (e.g., during gymnastics and running).
Sural Nerve:
- Formed by branches of the tibial nerve and the lateral sural cutaneous nerve.
- Supplies skin of the lateral and posterior part of the inferior third of the leg and the lateral sides of the foot.
- Used for nerve grafting in procedures to repair nerve defects from wounds.

Arteries of the Lower Limb

Femoral Artery:
- Chief artery to the lower limb; continuation of the external iliac artery.
Deep Artery of the Thigh:
- Chief artery to the thigh.
Popliteal Artery:
- Continuation of the femoral artery.
Anterior and Posterior Tibial Arteries:

Anterior Tibial Artery

Ends at the ankle joint and becomes the dorsalis pedis artery.

Dorsalis Pedis Artery (Dorsal Artery of the Foot)

Continuation of the anterior tibial artery.
Begins midway between the malleoli and runs anteromedially, deep to the inferior extensor retinaculum.
Divides into:
- Deep plantar artery (passes to the sole).
- 1st dorsal metatarsal artery.
- Arcuate artery.
Dorsalis Pedis Pulse: Used in physical examination of the peripheral vascular system.

Arcuate Artery

Runs across the bases of the lateral four metatarsals, deep to the extensor tendons.
Gives rise to the 2nd, 3rd, and 4th dorsal metatarsal arteries.
Provides perforating branches to the plantar metatarsal arteries and dorsal digital arteries.

Posterior Tibial Artery

Located deep to the flexor retinaculum and the origin of the abductor hallucis; divides into the medial and lateral plantar arteries.

Medial and Lateral Plantar Arteries

Run parallel to the similarly named nerves.
Medial Plantar Artery:
- Smaller; mainly supplies muscles of the great toe.
Lateral Plantar Artery:
- Larger than the medial plantar artery; runs laterally and anteriorly, arches medially across the foot to form the deep plantar arch.

Deep Plantar Arch

Begins opposite the base of the 5th metatarsal.
Completed medially by the union with the deep plantar artery, a branch of the dorsal artery of the foot.
Gives off four plantar metatarsal arteries, which provide the plantar digital arteries.

Superficial Veins of the Lower Limb

Located in the subcutaneous tissue.
Have valves, but fewer than deep veins.
Two Major Superficial Veins:
- Great saphenous vein (long).
- Small saphenous vein (short).

The Small (Short) Saphenous Vein

Arises on the lateral side of the foot from the union of the dorsal vein of the small toe with the dorsal venous arch.
Ascends posterior to the lateral malleolus as a continuation of the lateral marginal vein.
Passes along the lateral border of the calcaneal tendon.
Inclines to the midline of the fibula and penetrates the deep fascia.
Ascends between the heads of the gastrocnemius muscle.
Empties into the popliteal vein in the popliteal fossa.

The Great (Long) Saphenous Vein

Formed by the union of the dorsal vein of the great toe and the dorsal venous arch of the foot (medial marginal vein).
Ascends anterior to the medial malleolus.
Anastomoses freely with the small saphenous vein.
Contains 10 to 12 valves, more numerous in the leg than in the thigh.
Commonly used for coronary arterial bypass due to:
- Accessibility.
- Sufficient distance between segments.

Lower Limb Anatomy Overview

Key Vascular Structures

Femoral Artery: Major artery supplying blood to the lower limb.
Femoral Vein: Accompanies the femoral artery, draining blood from the lower limb.
Saphenous Nerve: Provides sensory innervation to the skin of the medial leg and foot.
Descending Genicular Artery: A branch of the femoral artery contributing to the blood supply around the knee.
Nerve to Vastus Medialis: Innervates the vastus medialis muscle, part of the quadriceps group.

Popliteal Fossa

The popliteal fossa is a diamond-shaped depression located at the posterior aspect of the knee. It is formed by:

Posterior Boundaries:
- Skin and fascia, including the superficial popliteal fascia which contains fat and the small saphenous vein.
- Deep popliteal fascia, a strong sheath providing protection for neurovascular structures.
Superolateral Boundary: Biceps femoris muscle.
Superomedial Boundary: Semimembranosus and semitendinosus muscles.
Inferolateral Boundary: Lateral head of the gastrocnemius muscle and plantaris muscle.
Inferomedial Boundary: Medial head of the gastrocnemius muscle.
Anterior Boundary: Popliteal surface of the femur, oblique popliteal ligament, and popliteus muscle.

Contents of the Popliteal Fossa

Common fibular nerve
Tibial nerve
Popliteal vein
Popliteal artery
Posterior cutaneous nerve of the thigh
Small saphenous vein
Popliteal lymph nodes and lymphatic vessels

Popliteal Artery

The popliteal artery is the continuation of the femoral artery and gives rise to five genicular arteries that form a network around the knee:

Superior lateral
Medial superior
Middle
Inferior lateral
Inferior medial

The popliteal artery ends at the lower border of the popliteus muscle, dividing into the anterior and posterior tibial arteries.

Crural Fascia (Deep Fascia of the Leg)

Attaches to the anterior and medial borders of the tibia.
Continuous with the tibial periosteum.
Forms thickened bands (retinacula) in the distal part.
Interosseous membrane and intermuscular septa divide the leg into three compartments.
Transverse intermuscular septum separates superficial and deep plantarflexor muscles.

Muscles of the Anterior Compartment

Tibialis Anterior Muscle:
- Slender muscle against the lateral surface of the tibia.
- Strongest dorsiflexor and inverter of the foot.
- Innervated by the deep fibular nerve.
Extensor Digitorum Longus Muscle:
- Most lateral of the anterior leg muscles.
- Extends the lateral four digits and dorsiflexes the ankle.
- Innervated by the deep fibular nerve.
Fibularis Tertius Muscle:
- Part of the extensor digitorum longus.
- Attaches to the 5th metatarsal.
- Not always present; aids in dorsiflexion and eversion of the foot.
- Innervated by the deep fibular nerve.
Extensor Hallucis Longus Muscle:
- Thin muscle that extends the great toe and dorsiflexes the ankle.
- Innervated by the deep fibular nerve.

Muscles of the Lateral Compartment

Fibularis Longus Muscle:
- Longer and more superficial than fibularis brevis.
- Everts the foot and weakly plantarflexes the ankle.
- Innervated by the superficial fibular nerve.
Fibularis Brevis Muscle:
- Shorter and lies deep to fibularis longus.
- Also everts the foot and weakly plantarflexes the ankle.
- Innervated by the superficial fibular nerve.

Muscles of the Posterior Compartment

Superficial Muscle Group:
- Includes gastrocnemius, soleus, and plantaris muscles.
- Powerful group responsible for plantarflexion of the foot.
- Gastrocnemius is a two-headed muscle acting on both the knee and ankle joints.
- Innervated by the tibial nerve.
Deep Muscle Group:
- Flexor Digitorum Longus Muscle:
  - Flexes the lateral four digits and plantarflexes the ankle.
  - Innervated by the tibial nerve.
- Flexor Hallucis Longus Muscle:
  - Flexes the great toe and supports the medial longitudinal arches of the foot.
  - Innervated by the tibial nerve.
- Tibialis Posterior Muscle:
  - Deepest muscle, plantarflexes and inverts the foot.
  - Innervated by the tibial nerve.
- Popliteus Muscle:
  - Forms the inferior part of the floor of the popliteal fossa.
  - Innervated by the tibial nerve.

Neurovascular Structures

Sural Nerve:
- Formed by branches of the tibial nerve and lateral sural cutaneous nerve.
- Supplies skin of the lateral and posterior part of the leg and lateral side of the foot.
Anterior Tibial Artery:
- Supplies structures in the anterior compartment.
- Becomes the dorsalis pedis artery at the ankle joint.
Posterior Tibial Artery:
- Larger terminal branch of the popliteal artery; main blood supply to the foot.
- Divides into medial and lateral plantar arteries.

Tarsal Tunnel

Located in the medial malleolar region, the tarsal tunnel allows neurovascular structures and deep flexor tendons to pass from the deep flexor compartment to the plantar side of the foot. Tarsal tunnel syndrome may present with:

Pain
Numbness
Tingling sensations

Foot Anatomy

The foot, located distal to the leg, supports body weight and plays a crucial role in locomotion. Key features include:

Plantar Surface: The part of the foot facing the ground.
Dorsal Surface: The part facing superiorly.
Thin deep fascia on the dorsum, continuous with the plantar fascia.

Muscles of the Dorsum of the Foot

Extensor Digitorum Brevis: Extends the 2nd to 4th digits at the metatarsophalangeal joints.
Extensor Hallucis Brevis: Extends the great toe.
Both muscles are innervated by the deep fibular nerve.

Deep Fascia of the Sole

This fascia holds the parts of the foot together, protects the plantar surface from injury, and supports the longitudinal arches of the foot. The plantar aponeurosis is a strong, thick central part of the deep fascia that divides into five bands, enclosing digital tendons.

Muscles of the Sole

Medial Compartment:
- Abductor Hallucis: Abducts and flexes the great toe.
- Flexor Hallucis Brevis: Flexes the proximal phalanx of the great toe.
- Adductor Hallucis: Adducts the great toe and assists in maintaining the transverse arch.
Lateral Compartment:
- Abductor Digiti Minimi: Abducts and flexes the 5th digit.
- Flexor Digiti Minimi Brevis: Flexes the proximal phalanx of the 5th digit.
Central Compartment:
- Flexor Digitorum Brevis: Flexes the 4 digits.
- Quadratus Plantae: Assists flexor digitorum longus in flexing the lateral four digits.
- Lumbricals: Flex proximal phalanges and extend middle and distal phalanges of the lateral four digits.

Lower Limb Anatomy: Anterior and Medial Thigh Muscles

Anterior Thigh Muscles

Sartorius
- Longest muscle in the body, approximately 15 cm long.
- Acts across two joints: hip and knee.
- Actions:
  - Flexes the hip joint.
  - Participates in knee flexion.
  - Weakly abducts and laterally rotates the thigh.
- Innervation: Primarily by the femoral nerve; sometimes by the intermediate cutaneous nerve of the thigh.
Quadriceps Femoris
- Four-headed muscle forming the bulk of the anterior thigh.
- Greatest extensor of the leg.
- Tendons of the four parts unite to form a broad distal tendon.
- Distal Attachment: Base of the patella and via the patellar ligament to the tibial tuberosity.
- Parts of Quadriceps Femoris:
  - Rectus Femoris
    - Runs straight down the thigh.
    - Assists iliopsoas in hip flexion.
    - Proximal attachment: Anterior inferior iliac spine and ilium, superior to acetabulum.
    - Innervation: Femoral nerve.
  - Vastus Lateralis
    - Largest component of the quadriceps.
    - Located on the lateral side of the thigh.
    - Proximal attachment: Greater trochanter of femur and lateral lip of linea aspera.
    - Innervation: Femoral nerve.
  - Vastus Medialis
    - Covers the medial side of the thigh.
    - Proximal attachment: Intertrochanteric line and medial lip of linea aspera of femur.
    - Innervation: Femoral nerve.
  - Vastus Intermedius
    - Located deep to the rectus femoris.
    - Proximal attachment: Anterior and lateral surfaces of the femur.
    - Innervation: Femoral nerve.
- Articular Muscle of the Knee
  - Small, flat muscle located deep to vastus intermedius.
  - Attaches to the anterior aspect of the femur and synovial membrane of the knee joint.
  - Actions:
    - Extends the leg at the knee joint.
    - Assists in climbing, running, jumping, and rising from a seated position.
    - Prevents compression of the synovial capsule during knee extension.

Medial Thigh Muscles

Gracilis
- Only medial thigh muscle that crosses the knee joint.
- Long, strap-like muscle located along the medial side of the thigh and knee.
- Attachment: Extends from the body and inferior ramus of the pubis to the medial surface of the tibia.
- Actions:
  - Adducts the thigh.
  - Flexes the leg.
  - Medially rotates the leg.
- Innervation: Anterior branch of the obturator nerve.
Pectineus
- Flat, quadrangular muscle located in the anterior part of the superomedial thigh.
- Attachment: Extends from the superior ramus of the pubis to the pectineal line of the femur.
- Actions:
  - Adducts the thigh.
  - Flexes the thigh.
  - Assists in medial rotation of the thigh.
- Innervation: Primarily by the femoral nerve; sometimes by the obturator nerve.
Adductor Longus
- Large, fan-shaped muscle, most anteriorly placed among the adductors.
- Attachment: Extends from the body of the pubis to the middle third of the linea aspera of the femur.
- Action: Adducts the thigh.
- Innervation: Anterior branch of the obturator nerve.
Adductor Brevis
- Short muscle located deep to pectineus and adductor longus.
- Attachment: Extends from the body and inferior ramus of the pubis to the pectineal line and proximal part of the linea aspera of the femur.
- Actions:
  - Adducts and flexes the thigh.
- Innervation: Obturator nerve.
Adductor Magnus
- Largest muscle of the medial thigh.
- Composite, triangular muscle with two parts.
- Adductor Part: Extends from the inferior ramus of the pubis.

Femur and Associated Muscles

The femur is the longest bone in the human body, playing a crucial role in supporting the weight of the body and facilitating movement. Understanding the muscles associated with the femur, particularly those involved in hip joint movement, is essential for comprehending lower limb mechanics.

Obturator Internus Muscle

Location: Partly situated in the pelvis, covering most of the lateral wall.
Attachments:
- Proximal: Pelvic surface of the obturator membrane and surrounding bones.
- Distal: Exits the pelvis through the lesser sciatic foramen, becoming tendinous as it attaches to the medial surface of the greater trochanter.
Innervation: Innervated by the nerve to the obturator internus (L5 and S1), along with the superior gemellus muscle.

Superior and Inferior Gemelli

Assist the obturator internus muscle.
Origins:
- Superior Gemellus: Arises from the ischial spine.
- Inferior Gemellus: Arises from the ischial tuberosity.
Function: Both run to the medial surface of the greater trochanter (trochanteric fossa) of the femur, aiding in lateral rotation of the extended thigh and abduction of the flexed thigh, while stabilizing the femoral head in the acetabulum.

Quadratus Femoris

Description: A short, flat, quadrangular muscle located inferior to the obturator internus and gemelli muscles.
Attachments:
- Runs from the lateral border of the ischial tuberosity to the quadrate tubercle on the intertrochanteric crest of the femur and the area inferior to it.
Innervation: Innervated by the nerve to quadratus femoris (L5 and S1).
Action: Primarily responsible for lateral rotation of the thigh and stabilizing the femoral head in the acetabulum.

Obturator Externus

Location: Deep in the thigh, posterior to the pectineus and superior ends of the adductor muscles.
Attachments:
- Originates from the obturator foramen and membrane.
- The tendon passes deep to the quadratus femoris to attach to the trochanteric fossa of the femur.
Function: Stabilizes the head of the femur in the acetabulum, acts as a lateral rotator of the thigh, and assists in adduction.

Movements of the Hip Joint

Flexors:
- Iliopsoas (strongest flexor)
- Sartorius
- Tensor of fascia lata
- Rectus femoris
- Pectineus
- Adductor muscles: Longus, Brevis, Magnus (anterior part), Gracilis
Extensors:
- Hamstrings: Semitendinosus, Semimembranosus, Biceps femoris (long head)
- Adductor magnus (posterior part)
- Gluteus maximus
Abductors:
- Gluteus medius
- Gluteus minimus
- Tensor of fascia lata
Adductors:
- Adductor muscles: Longus, Brevis, Magnus, Gracilis, Pectineus, Obturator externus
Medial Rotators:
- Gluteus medius (anterior part)
- Gluteus minimus (anterior part)
- Tensor of fascia lata
Lateral Rotators:
- Obturator externus
- Obturator internus
- Gemelli (superior and inferior)
- Piriformis
- Quadratus femoris
- Gluteus maximus

Greater and Lesser Sciatic Foramen

Greater Sciatic Foramen:
- Bordered by the greater sciatic notch and the sacrospinous ligament.
- Allows passage of the piriformis muscle and structures entering or leaving the pelvis, including:
  - Superior gluteal vessels and nerve (superior orifice)
  - Inferior gluteal vessels and nerve (inferior orifice)
  - Sciatic nerve
  - Posterior cutaneous nerve of the thigh
  - Internal pudendal vessels
  - Pudendal nerve
Lesser Sciatic Foramen:
- Bounded by the lesser sciatic notch, sacrospinous ligament, and sacrotuberous ligament.
- Allows passage of the tendon of the obturator internus muscle, pudendal nerve, and internal pudendal vessels.

Lumbar Plexus

Location: Found in the posterior part of the psoas major muscle, anterior to the lumbar transverse processes.
Composition: Formed by the ventral rami of L1 through L4 nerves, receiving gray communicating rami from the sympathetic trunks.
Major Branches:
- Femoral nerve
- Obturator nerve
- Lumbosacral trunk: Descends into the pelvis to form the sacral plexus.
- Ilioinguinal and iliohypogastric nerves: Supply the skin of the suprapubic and inguinal regions.
- Genitofemoral nerve: Divides into femoral and genital branches after piercing the psoas major muscle.
- Lateral femoral cutaneous nerve: Supplies the anterolateral surface of the thigh.

Femoral Nerve

Overview: The largest branch of the lumbar plexus, composed of L2 through L4.
Pathway: Emerges from the lateral border of the psoas major muscle, descends through the pelvis, and passes deep to the inguinal ligament into the femoral triangle.
Branches: Divides into several branches supplying the anterior thigh muscles and providing articular branches to the hip and knee joints.
Saphenous Nerve: The terminal cutaneous branch that accompanies the femoral artery and vein through the adductor canal, supplying the skin and fascia on the anteromedial aspect of the knee, leg, and foot.

Obturator Nerve

Origin: Arises from the lumbar plexus in the abdomen and enters the lesser pelvis.
Pathway: Runs in the extraperitoneal fat along the lateral wall of the pelvis to the obturator canal.
Function: Divides into anterior and posterior parts, supplying the medial thigh muscles (adductor muscles).

Obturator Canal

Definition: Bounded by the obturator groove and opening in the obturator membrane, allowing passage of the obturator nerve and vessels from the pelvic cavity into the thigh.

Sacral Plexus

Location: Situated on the posterolateral wall of the lesser pelvis, related to the anterior surface of the piriformis muscle.
Composition: Formed by the ventral rami of L5 through S4 nerves, with connections to the lumbar plexus via the lumbosacral trunk.
Main Nerves: Includes the sciatic and pudendal nerves, which lie external to the parietal pelvic fascia.
Branches: Most exit the pelvis through the greater sciatic foramen.

Sciatic Nerve

Overview: The largest nerve in the body, composed of L4 to S3.
Pathway: Passes through the greater sciatic foramen, inferior to the piriformis, entering the gluteal region.
Function: Descends along the posterior aspect of the thigh, supplying the knee flexors and all muscles in the leg and foot.

Pudendal Nerve

Origin: Composed of S2 to S4.
Function: The main nerve of the perineum and chief sensory nerve of the external genitalia, accompanied by internal pudendal vessels.
Pathway: Leaves the pelvis through the greater sciatic foramen, hooks around the ischial spine and sacrospinous ligament, and enters the perineum through the lesser sciatic foramen.

Superior and Inferior Gluteal Nerves

Superior Gluteal Nerve:
- Origin: L4 to S1.
- Pathway: Leaves the pelvis through the greater sciatic foramen superior to the piriformis.
- Function: Supplies the gluteus medius, gluteus minimus, and tensor of fascia lata.
Inferior Gluteal Nerve:
- Origin: L5 to S2.
- Pathway: Leaves the pelvis through the greater sciatic foramen inferior to the piriformis and superficial to the sciatic nerve.
- Function: Supplies the gluteus maximus.

Posterior Femoral Cutaneous Nerve

Origin: Composed of S2 to S3.
Pathway: Leaves the pelvis through the greater sciatic foramen inferior to the piriformis.
Function: Supplies the skin of the buttock and uppermost medial and posterior surfaces of the thigh.

Common Iliac Artery

Origin: Begins at the aortic bifurcation at the level of L4.
Pathway: Diverges and runs inferolaterally, following the medial border of the psoas muscles to the pelvic brim.
Branches: At the pelvic brim, each artery divides into the internal and external iliac arteries.

Posterior Femoral Cutaneous Nerve

The posterior femoral cutaneous nerve is a significant nerve that originates from the sacral plexus, specifically from the S2 to S3 spinal nerves.

Pathway: It exits the pelvis through the greater sciatic foramen, located inferior to the piriformis muscle.
Function: This nerve supplies sensation to the skin of the buttock and the uppermost medial and posterior surfaces of the thigh.

Common Iliac Artery

The common iliac arteries are major blood vessels that begin at the bifurcation of the aorta at the level of L4.

Pathway: They diverge and run inferolaterally, following the medial border of the psoas muscles until they reach the pelvic brim.
Division: At the pelvic brim, each common iliac artery divides into the internal and external iliac arteries.

External Iliac Artery

The external iliac artery is a continuation of the common iliac artery and plays a crucial role in supplying blood to the lower limb.

Pathway: It follows the iliopsoas muscle and gives rise to two important branches before leaving the abdomen:

Inferior Epigastric Artery: Supplies the anterolateral abdominal wall and runs superiorly into the rectus sheath, deep to the rectus abdominis muscle.
Deep Circumflex Iliac Artery: Runs parallel to the inguinal ligament and supplies the iliacus muscle and the inferior part of the anterolateral abdominal wall.

Termination: The external iliac artery ends at the inguinal ligament, where it continues as the femoral artery.

Femoral Sheath

The femoral sheath is a funnel-shaped fascial tube that plays a vital role in the anatomy of the femoral vessels.

Structure: It extends 3 to 4 cm inferior to the inguinal ligament and encloses the proximal parts of the femoral vessels and the femoral canal.
Composition: Formed by an inferior prolongation of the transversalis and iliopsoas fascia from the abdomen.
Exclusions: The femoral sheath does not enclose the femoral nerve.
Function: It allows the femoral artery and vein to glide beneath the inguinal ligament during hip joint movements.
Compartments: The femoral sheath is divided into three compartments by vertical septa:

Lateral compartment for the femoral artery
Intermediate compartment for the femoral vein
Medial compartment, known as the femoral canal

Internal Iliac Artery

The internal iliac artery is a critical vessel of the pelvis, providing blood supply to various pelvic structures.

Origin: Each internal iliac artery begins anterior to the sacroiliac joint at the bifurcation of the common iliac artery and descends posteriorly to the greater sciatic foramen.
Branches: The internal iliac artery typically ends at the superior edge of the greater sciatic foramen, dividing into anterior and posterior divisions.
Anterior Division: Primarily visceral branches supplying the bladder, rectum, and reproductive organs, along with two parietal branches to the buttock and thigh.
Key Branches of the Anterior Division:

Umbilical Artery
Obturator Artery: Arises close to the umbilical artery, runs anterolaterally, and supplies medial thigh muscles.
Inferior Vesical Artery
Middle Rectal Artery
Vaginal Artery
Uterine Artery
Internal Pudendal Artery: Supplies the perineum, dividing into deep and dorsal arteries of the penis and clitoris.
Inferior Gluteal Artery: Supplies muscles and skin of the buttock and posterior thigh.
Superior Gluteal Artery: Supplies gluteal muscles and leaves the pelvis via the superior part of the greater sciatic foramen.
Iliolumbar and Lateral Sacral Arteries

Anterior Thigh Muscles

The anterior compartment of the thigh contains several important muscles, including the sartorius.

Sartorius: The longest muscle in the body, approximately 15 cm long.
Function: Acts across two joints, primarily flexing the hip joint and assisting in the flexion of the knee.

Connective Tissue and Vascular Structures of the Lower Limb

Connective Tissue Layers

A dense layer of connective tissue is situated between the subcutaneous tissue and muscles, serving several critical functions:

Fibrous Septa Formation: This connective tissue forms fibrous septa, both lateral and medial, which separate muscles from one another and invest them.
Muscle Contraction Efficiency: By preventing the bulging of muscles during contraction, this tissue enhances the efficiency of muscular contractions, particularly in pumping blood toward the heart.
Attachment Points: It attaches to various anatomical landmarks, including:
- Inguinal ligament
- Pubic arch
- Body of pubis
- Pubic tubercle
- Iliac crest
- Sacrum
- Coccyx
- Sacrotuberous ligament
- Ischial tuberosity

Saphenous Opening

The saphenous opening is a significant anatomical feature characterized by:

Location: It is a deficiency in the fascia lata located inferior to the medial part of the inguinal ligament, approximately 4 cm inferolateral to the pubic tubercle.
Margins: The smooth medial margin is complemented by lateral, superior, and inferior margins that form the falciform margin.
Cribriform Fascia: This area contains fibrofatty tissue and is where the great saphenous vein drains into the femoral vein.
Lymphatic Drainage: Some efferent lymphatic vessels from the superficial inguinal lymph nodes enter the deep inguinal lymph nodes.

Femoral Canal

The femoral canal is the smallest of the three compartments within the femoral sheath:

Dimensions: It is short, measuring approximately 1.25 cm.
Shape: Though oval-shaped, the base of the abdominal end is directed superiorly and is referred to as the femoral ring.
Function: It extends distally to the proximal edge of the saphenous opening and allows for the expansion of the femoral vein.
Contents: The femoral canal contains:
- Loose connective tissue
- Fat
- Lymphatic vessels
- Deep inguinal lymph node (Rosenmüller lymph node)

Femoral Ring

The femoral ring is the small proximal opening of the femoral canal:

Closure: It is closed by extraperitoneal fatty tissue known as the femoral septum and is covered by parietal peritoneum.
Lymphatic Connections: It is pierced by lymphatic vessels that connect the inguinal and external iliac lymph nodes.
Boundaries: The femoral ring is defined by:
- Laterally: Between the femoral canal and femoral vein
- Posteriorly: The superior ramus of the pubis
- Medially: The lacunar ligament
- Anteriorly: The medial part of the inguinal canal

Femoral Artery

The femoral artery is the chief artery supplying the lower limb:

Origin: It is a continuation of the external iliac artery, beginning at the inguinal ligament and passing midway between the anterior superior iliac spine and the pubic symphysis.
Pulse Location: The femoral pulse can be palpated just inferior to the mid-inguinal point.
Course: It runs down to the adductor canal, passing through the adductor hiatus to become the popliteal artery.
Branches: It gives off the descending genicular artery.

Deep Artery of the Thigh

The deep artery of the thigh is the largest branch of the femoral artery:

Function: It serves as the chief artery to the thigh.
Location: It passes deeply into the thigh, lying posterior to the femoral artery and vein on the medial side of the femur.
Exit Point: It leaves the femoral triangle between the pectineus and adductor longus muscles.
Circumflex Femoral Arteries: The medial and lateral circumflex femoral arteries encircle the thigh and anastomose with each other and other arteries, with the medial circumflex being the most important source of blood to the femoral head and neck.

Femoral Triangle

The femoral triangle is a junctional region between the trunk and lower limb:

Location: It is a triangular fascial space located in the superoanterior third of the thigh.
Boundaries: The triangle is defined by:
- Superiorly: The inguinal ligament
- Medially: The adductor longus muscle
- Laterally: The sartorius muscle
- Muscular Floor: Iliopsoas and pectineus muscles
- Roof: Fascia lata, cribriform fascia, subcutaneous tissue, and skin
Contents: The femoral triangle contains:
- Femoral nerve and its branches
- Femoral artery and its branches
- Femoral vein and its proximal tributaries (including the great saphenous and deep femoral veins)
- Inguinal lymph nodes and lymphatic vessels

Adductor Canal

The adductor canal is a narrow fascial tunnel:

Length: Approximately 15 cm long, it runs from the apex of the femoral triangle to the adductor hiatus in the tendon of the adductor magnus muscle.
Boundaries: The canal is bordered by:
- Vastus medialis
- Adductor magnus
- Adductor longus
- Sartorius
- Anteromedial intermuscular septum
Contents: The adductor canal contains:
- Femoral artery
- Femoral vein
- Saphenous nerve
- Descending genicular artery
- Nerve to vastus medialis

Popliteal Fossa

The popliteal fossa is a diamond-shaped depression located at the posterior aspect of the knee:

Formation: It is formed posteriorly by skin and fascia, including:
- Superficial popliteal fascia, which contains fat and the small saphenous vein.

Deep Fascia and Veins of the Lower Limb

Deep Fascia

Deep fascia ascends between the heads of the gastrocnemius muscle.
It empties into the popliteal vein located in the popliteal fossa.

The Great (Long) Saphenous Vein

Formation:
- Formed by the union of the dorsal vein of the great toe and the dorsal venous arch of the foot.
- Also known as the medial marginal vein.
Pathway:
- Ascends anterior to the medial malleolus.
- Anastomoses freely with the small saphenous vein.
- Passes posterior to the medial condyle of the femur.
- Transverses the saphenous opening in the fascia lata.
- Empties into the femoral vein.
Valves:
- Contains 10 to 12 valves, which are more numerous in the leg than in the thigh.
Clinical Significance:
- Commonly used for coronary arterial bypass due to:
  - Readily accessible location.
  - Sufficient distance between tributaries and perforating veins allows for usable length to be harvested.
  - Higher percentage of muscular and elastic fibers in its walls compared to other superficial veins.
Receives tributaries from:
- Superficial circumflex iliac vein.
- Epigastric vein.
- External pudendal veins.

Deep Veins of the Lower Limb

Location:
- Located deep to the deep fascia.
- Accompany all major arteries and their branches.
Characteristics:
- Have more numerous valves than superficial veins.
- Usually occur as paired veins that frequently interconnect, flanking the artery they accompany.
- Contained within a vascular sheath along with the artery, where the artery's pulsations help compress and move blood in the veins.
Communication:
- Communicate with superficial veins through perforating veins (communicating veins), which accompany the perforating arteries from the deep artery of the thigh.
- More variable and anastomose more frequently than the arteries they accompany.

Deep Vein Thrombosis (DVT) in Ultrasonography

Diagnosis:
- A vein cannot be compressed if a clot is present, preventing the vein from collapsing.

Lymphatic Drainage of the Lower Limb

Types of Lymphatic Vessels:
- Superficial and deep lymphatic vessels.
- Superficial lymphatic vessels accompany the saphenous veins and their tributaries in the superficial fascia.
Drainage Pathway:
- Lymphatic vessels along the great saphenous vein and circumflex superficial iliac vein drain into the superficial inguinal nodes.
- From superficial lymph nodes, lymph passes directly to the external iliac lymph nodes or to the deep inguinal lymph nodes.

Popliteal Lymph Nodes

Location:
- The lymphatic vessels accompanying the small saphenous vein enter the popliteal lymph nodes surrounding the popliteal vein in the fat of the popliteal fossa.
- Deep lymphatic vessels from the leg accompany deep veins and enter the popliteal lymph nodes.
Drainage:
- Lymph from the popliteal nodes ascends through deep lymphatic vessels, accompanying deep blood vessels to the deep inguinal nodes.

Deep Inguinal Lymph Nodes

Location:
- Lie under the superficial fascia on the medial aspect of the femoral vein.
Drainage:
- Lymph from the deep inguinal lymph nodes passes to the external iliac lymph nodes.

External Iliac Lymph Nodes

Location:
- Located along the external iliac vein.
Drainage:
- Lymph from these nodes passes to the common iliac lymph nodes and then to the lumbar lymph nodes.
- Lumbar lymph nodes form lumbar lymphatic trunks.

Muscles of the Thigh

Adductor Muscles

Adductor Brevis
- Location: Lies deep to the pectineus and adductor longus muscles.
- Type: Short adductor muscle.
- Attachment: Extends from the body and inferior ramus of the pubis to the pectineal line and proximal part of the linea aspera of the femur.
- Action:
  - Adducts the thigh.
  - Flexes the thigh.
- Innervation: Obturator nerve.
Adductor Magnus
- Size: The largest muscle of the medial thigh.
- Type: Composite, triangular muscle with two parts.
- Attachments:
  - Adductor Part: Extends from the inferior ramus of the pubis to the gluteal tuberosity, linea aspera, and medial supracondylar line.
  - Hamstring Part: Extends from the ischial tuberosity to the adductor tubercle of the femur.
- Actions:
  - Adducts the thigh.
  - Adductor part flexes the thigh.
  - Hamstring part extends the thigh.
- Innervation:
  - Adductor part: Posterior branch of the obturator nerve.
  - Hamstring part: Sciatic nerve.

Actions of Med

Lower Limb Anatomy: Muscles, Nerves, and Vessels

Lower Limb Anatomy: Muscles, Nerves, and Vessels