Anterior Pelvic Girdle & Thigh: Comprehensive Study Notes

Surface Anatomy

• Key regions & palpable landmarks
  • Anterior abdominal wall
  • Back / Gluteal region
  • Anterior Superior Iliac Spine (ASIS)
  • Inguinal ligament (runs ASIS → pubic tubercle)
  • Pubic tubercle & pubic symphysis
  • Iliac crest (outer & inner lips, intermediate zone)
  • Gluteal fold (inferior border gluteus maximus)
  • Anterior & posterior thigh, knee joint, leg, ankle joint, foot

Femoral Triangle

• Boundaries
  • Superior: inguinal ligament
  • Lateral: medial margin of sartorius
  • Medial: medial margin adductor longus
  • Floor: iliopsoas (lat) + pectineus (med)
  • Roof: fascia lata & skin
• Contents (lat → med):
  • Femoral nerve (+ terminal branches)
  • Femoral artery
  • Femoral vein
  • Lymphatics (femoral canal)
  • Mnemonic: NAVeL (Nerve–Artery–Vein–empty space–Lacunar lig.)
• Surface landmarks: ASIS, pubic tubercle, pubic symphysis

Posterior Leg & Popliteal Fossa

• Boundaries formed by biceps femoris, semimembranosus/semitendinosus, gastrocnemius heads
• Contents (superficial → deep)
  • Small saphenous vein (penetrates deep fascia)
  • Tibial nerve & common fibular nerve bifurcating from sciatic
  • Popliteal artery (continuation femoral) & popliteal vein
  • Head of fibula as palpable lateral landmark

Bones of the Lower Limb

• Pelvic bone (hip/coxal): ilium, ischium, pubis fused at acetabulum
• Femur (largest, longest, strongest)
• Patella (sesamoid in quadriceps tendon)
• Tibia (weight-bearing) & Fibula (lateral support)
• Tarsals, metatarsals, phalanges

Key Joints & Classification

• Hip: Ball-and-socket,
  \text{multiaxial synovial}
  
• Knee
  • \text{Femur + Tibia: modified hinge} (flex/extend, slight rotation)
  • \text{Femur + Patella: plane} (sesamoid glide)
• Proximal tibiofibular: plane synovial
• Distal tibiofibular: fibrous syndesmosis
• Ankle (talocrural): hinge, uniaxial synovial
• Intertarsal & tarsometatarsal: plane synovial
• Metatarsophalangeal: condyloid synovial
• Interphalangeal: hinge uniaxial

Pelvic (Innominate) Bone Landmarks

Ilium

• ASIS, AIIS, PSIS, PIIS
• Iliac crest (outer/inner lips, intermediate zone, tuberculum)
• Gluteal lines: anterior, posterior, inferior (origins gluteal mm.)
• Greater sciatic notch, iliac fossa, arcuate line, iliac tuberosity, auricular surface for sacrum

Pubis

• Body, superior & inferior pubic rami
• Pubic tubercle, symphyseal surface, pecten pubis (pectineal line)
• Obturator crest, obturator foramen (closed by obturator membrane)

Ischium

• Ischial spine, ischial tuberosity ("sit bone"), ramus of ischium
• Lesser sciatic notch

Acetabulum

• Lunate articular surface, acetabular notch, limbus (margin)

Pelvic Ligaments & Sciatic Foramina

• Sacrospinous: attaches sacrum → ischial spine; converts greater sciatic notch to greater sciatic foramen
• Sacrotuberous: sacrum → ischial tuberosity; closes lesser sciatic foramen posteriorly/inferiorly
• Sacroiliac (anterior & posterior), iliolumbar, pubofemoral, iliofemoral, ischiofemoral reinforce pelvis & hip
• Greater Sciatic Foramen contents
  • Piriformis (lands mark muscle)
  • Superior to piriformis: superior gluteal nerve & vessels
  • Inferior to piriformis: "POPS IQ"—Pudendal nerve, n. to Obturator internus, Posterior femoral cutaneous, Sciatic, Inferior gluteal vessels/nerve, n. to Quadratus femoris
• Lesser Sciatic Foramen contents: pudendal neurovascular bundle & obturator internus tendon/nerve

Weight Transfer Pathway

\text{Vertebral column} \rightarrow \text{Sacroiliac joints} \rightarrow \text{Ilium (dense column)} \rightarrow \text{Acetabulum} \rightarrow \text{Femoral head/neck} \rightarrow \text{Femoral shaft} \rightarrow \text{Tibia}

• Thick iliac column + thin ala for muscle attachment
• Line of gravity passes posterior to hip joint, anterior to knee, through ankle

Femur: Detailed Anatomy

Proximal

• Head (fovea capitis for ligamentum teres)
• Neck (common # site)
• Greater trochanter (sup/lat), lesser trochanter (med/inf) – joined anteriorly by intertrochanteric line, posteriorly by intertrochanteric crest (with trochanteric fossa)
• Calcar femorale: internal strut reinforcing neck

Shaft

• Linea aspera (medial & lateral lips)
  • Pectineal line (medial branch) & gluteal tuberosity (lateral branch)
• Nutrient foramen (directed superiorly)

Distal

• Medial & lateral condyles (articulate with tibia)
• Medial & lateral epicondyles (ligament attachment)
• Intercondylar fossa (cruciate lig. residence)
• Adductor tubercle (insertion adductor magnus hamstring part)
• Supracondylar lines (continuation linea aspera)

Tibia, Fibula, Patella

Tibia

• Medial & lateral condyles → tibial plateaus (articulate with femur)
• Intercondylar eminence (ACL/PCL attach)
• Tibial tuberosity (patellar ligament attachment) – Osgood-Schlatter disease (traction apophysitis)
• Medial malleolus (ankle mortise)

Fibula

• Head (biceps femoris insertion, common fibular nerve wraps)
• Shaft + lateral malleolus (forms lateral ankle mortise)

Patella

• Triangular sesamoid within quadriceps tendon
• Posterior surface articulates with femoral trochlea (femoral groove)
• Variants
  • Patella alta: positioned proximally in trochlear groove → instability
  • Patella baja: distal position, often post-operative/trauma → pain

Lumbosacral Plexus Overview

Lumbar Plexus (L1–L4, in psoas major)

• Femoral n.
  • Motor: anterior thigh (quadriceps, sartorius, iliacus, pectineus)
  • Cutaneous: anterior thigh, medial leg/foot via saphenous
• Obturator n.
  • Motor: adductor group
  • Sensory: medial thigh, hip & knee joints
• Lateral femoral cutaneous n.: skin of lateral thigh (entrapment = meralgia paresthetica)
• Genitofemoral n.: skin scrotum/labia, anterior thigh; motor to cremaster

Sacral Plexus (L4–S4, anterior to piriformis)

• Sciatic n. (tibial + common fibular divisions)
  • Tibial division: posterior leg, sole (motor & sensory)
  • Common fibular division: anterior/lateral leg & dorsum foot (motor & sensory)
• Superior gluteal n.: gluteus medius, minimus, TFL
• Inferior gluteal n.: gluteus maximus
• Posterior femoral cutaneous n.: inferior buttock, posterior thigh, popliteal fossa
• Pudendal n.: perineum sensory & motor (external genitalia, anal sphincters)

Cutaneous Nerves of Lower Extremity

• Illustrated anterior & posterior maps; include clunial (buttocks), saphenous, sural, superficial & deep fibular, etc.

Dermatomes & Myotomes (Key Testing Sites)

• Dermatomes (lower quarter)
  • L1: upper anterior thigh
  • L2: mid anterior thigh
  • L3: medial femoral condyle
  • L4: medial malleolus
  • L5: dorsum 3rd MTP
  • S1: lateral heel
  • S2: popliteal fossa
  • S3: ischial tuberosity
  • S4: perianal area
• Myotomes (motor screen)
  • L1-L3: \text{hip flexion}
  • L3-L4: \text{knee extension}
  • L4-L5: \text{dorsiflexion/inversion}
  • L5-S1: \text{great toe extension}

Blood Supply

Arterial Tree

• Abdominal aorta → common iliac → external & internal iliac
• Internal iliac branches
  • Superior & inferior gluteal arteries (to gluteal region)
  • Internal pudendal (perineum, external genitalia)
  • Obturator (through obturator canal to adductors)
• External iliac ⇒ passes under inguinal ligament ⇒ femoral artery
  • Profunda femoris (deep artery of thigh) → medial & lateral circumflex femoral arteries + perforating branches
  • Femoral ⇒ through adductor hiatus ⇒ popliteal artery
• Popliteal ⇒ anterior & posterior tibial; genicular branches to knee

Venous Drainage

• Deep veins accompany arteries → femoral → external iliac → IVC
• Superficial system
  • Dorsal venous arch → great saphenous (medial; drains into femoral) & small saphenous (posterior; drains into popliteal)

Muscles of Anterior Pelvis & Thigh

Iliopsoas Group

• Psoas major (T12–L5 bodies & discs → lesser trochanter): prime hip flexor
• Iliacus (iliac fossa → lesser trochanter)
• Psoas minor (T12–L1 → pectineal line/iliopectineal eminence); assists lumbar flexion, not a hip flexor

Tensor Fasciae Latae (TFL)

• PA: ASIS & anterior external lip iliac crest
• DA: IT band to Gerdy’s tubercle (lateral condyle tibia)
• Functions: hip flexion, abduction, medial rotation; maintains tension in ITB

Sartorius ("Tailor’s muscle")

• Longest muscle
• PA: ASIS & notch below
• DA: superior medial tibia (pes anserinus)
• Actions: flex, abduct, laterally rotate hip; flex knee

Quadriceps Femoris (4 heads)

1. Rectus femoris – PA AIIS & superior acetabulum
2. Vastus lateralis – PA greater trochanter & lateral linea aspera
3. Vastus medialis – PA intertrochanteric line & medial linea aspera
4. Vastus intermedius – PA anterior/lateral femoral shaft (deep)

• Common DA: quadriceps tendon → patella → patellar ligament → tibial tuberosity
• Function: knee extension; rectus also hip flexion

Medial (Adductor) Compartment

1. Pectineus – pecten pubis → pectineal line femur (hip flex/adduct)
2. Adductor longus – pubic body → middle linea aspera
3. Adductor brevis – pubic body & inferior ramus → pectineal line & proximal linea aspera
4. Gracilis – pubic body & inferior ramus → pes anserinus (only adductor crossing knee; assists flex/med-rot knee)
5. Adductor magnus
   • Adductor portion: inferior pubic ramus & ramus ischium → linea aspera & medial supracondylar line
   • Hamstring portion: ischial tuberosity → adductor tubercle (acts with hamstrings for hip extension)

Obturator Externus (deep, lateral rotator)

• PA: obturator membrane & foramen margins (external surface)
• DA: trochanteric fossa femur

Lateral Pelvis – IT Band Complex

• Gluteus maximus inserts into IT tract with TFL
• IT band → lateral condyle tibia (Gerdy’s tubercle); stabilises knee/hip

Pes Anserinus ("Say Grace before Tea/Supper")

• Medial proximal tibia tendinous confluence:
  1. Sartorius
  2. Gracilis
  3. Semitendinosus
• Underlain by pes anserine bursa (possible bursitis)

Femoral Triangle & Adductor Canal

• Femoral triangle boundaries/contents (see above)
• Adductor canal (Hunter’s): apex femoral triangle → adductor hiatus in adductor magnus
  • Contents: femoral artery & vein, saphenous nerve, nerve to vastus medialis
  • Ends as vessels become popliteal

Clinical Correlations & Pathologies

• Osgood–Schlatter disease: traction apophysitis of tibial tuberosity in adolescents (repetitive quadriceps pull)
• Meralgia paresthetica: entrapment lateral femoral cutaneous nerve under inguinal ligament → burning lateral thigh pain
• Patella alta/baja affecting patellofemoral mechanics → anterior knee pain
• Femoral neck fractures disrupt weight transfer; risk avascular necrosis (medial circumflex femoral artery)