Lower Limb – Hip, Thigh, Gluteal & Popliteal Region Review

Embryologic Development

• Limb buds: UE = wk 4; LE = wk 5 (L2–S2 somites).
• Early orientation: great toe & thumb point superiorly; soles/palms anterior.
• Torsion: LE undergoes medial rotation + pronation → great toe becomes medial, knee faces anterior & flexes posteriorly.
• Explains: dermatome spiral, opposite joint motions vs. UE, innervation rotations, WB priority.

Pelvic Girdle & Hip Osteology

• Pelvic girdle = Os coxae × 2 + sacrum.
• Greater pelvis (false) vs. lesser pelvis (true).
• Functions: weight transfer, viscera support, muscle attachment, fetal passage.
• Sex differences: female pelvis → wider inlet/outlet, larger sub-pubic angle, lighter bones.

Os Coxae Components

• Ilium
• Body forms acetabulum roof; ala = “wing.”
• Landmarks: ASIS, AIIS, PSIS, PIIS, iliac crest, anterior/posterior/inferior gluteal lines, iliac fossa, arcuate line, auricular surface, iliac tuberosity.
• Ischium
• Posteroinferior; contributes to acetabulum + obturator foramen.
• Landmarks: ischial spine, ischial tuberosity (origin – semimem., semiten., biceps fem., add. magnus), greater/lesser sciatic notches, ramus.
• Pubis
• Anteromedial; body + superior & inferior rami.
• Forms obturator foramen w/ ischial ramus.
• Landmarks: pubic crest, pubic tubercle (inguinal lig.), pecten pubis, symphysis (fibrocartilage disc).

Sacroiliac Joint (SIJ)

• Auricular surfaces = synovial; tuberosities = syndesmosis (interosseous lig.).
• Ligaments: anterior SI, interosseous SI (primary weight transfer), posterior SI, iliolumbar, sacrotuberous, sacrospinous.
• Sacrotuberous + sacrospinous convert sciatic notches → greater & lesser sciatic foramina; limit nutation.

Femur

• Longest/heaviest; ≈ ¼ body height.
• Proximal parts: head (fovea capitis), neck, greater/lesser trochanters, intertrochanteric line & crest, trochanteric fossa, gluteal tuberosity, pectineal line, \text{linea aspera}.
• Angles
• Inclination (neck–shaft): normal 115^{\circ}-140^{\circ} (avg 126^{\circ}).
• <105^{\circ} = coxa vara → ↑ shear @ neck, fracture risk; ↓ compressive DJD risk. • >140^{\circ} = coxa valga → ↑ compressive load, DJD; ↓ fracture.
• Torsion (version): neck vs. condylar line normal 15^{\circ}-20^{\circ} anteversion.
• Excess anteversion → toe-in; retroversion (<15°) → toe-out; often balanced by tibial torsion.
• Distal: medial/lateral condyles & epicondyles, intercondylar fossa, adductor tubercle, supracondylar ridges.

Coxafemoral (Hip) Joint

• Ball-and-socket: acetabulum + femoral head.
• Acetabulum: lunate articular surface, acetabular fossa, inferior notch. Labrum ↑ socket depth 10 %, encloses ½ head; “finestra” window equalizes pressure; site of femoro-acetabular impingement.
• Capsule: attaches to acetabular rim & neck; fibers spiral – tighten in extension (limit to 10–20°) & loosen in flexion.
• Ligaments
• Iliofemoral (Y of Bigelow) – AIIS → intertrochanteric line; strongest; prevents hyper-extension.
• Pubofemoral – pubic body/ramus → capsule; tight in extension & abduction.
• Ischiofemoral – posterior; ischial rim → neck; weakest.
• Ligamentum teres – acetabular notch → fovea; carries artery to head (obturator branch).

Lumbosacral Plexus

• Lumbar (L1–L4): chiefly thigh. Anterior divisions → medial thigh; posterior divisions → anterior thigh.
• Sacral (L4–S3): anterior divisions supply most posterior thigh/leg; posterior divisions supply gluteal, short head biceps, ant./lat. leg.

Key Root-Level Details

• L1: iliohypogastric, ilioinguinal (cutaneous); with L2 → genitofemoral (cremasteric reflex).
• L2: anterior part → obturator (w/ L3–4); posterior part → femoral & lateral femoral cutaneous.
• L3–4: obturator (ant) + femoral (post); accessory obturator (10 %).
• L4–S3: Sciatic (largest) = tibial (ant div) + common fibular (post div).
• Other posterior division nerves: Superior gluteal (L4–S1), Inferior gluteal (L5–S2), n. to piriformis, posterior femoral cutaneous.
• Other anterior division nerves: n. to quadratus femoris / obturator internus, pudendal.

Anterior Thigh Musculature

• Primary actions → hip flexion &/or knee extension.

Hip Flexors

• Pectineus – sup. pubic ramus → pectineal line; femoral ± obturator nn.; adducts + flexes ± rotates depending on position (Reimann 1996).
• Iliopsoas (iliacus + psoas major) – iliac fossa/TP L1–5 → lesser trochanter; femoral n. (iliacus) & L1–3 ventral rami (psoas); powerful flexor, lateral rotator.
• Psoas minor (≈40 % pop.) – T12–L1 bodies/discs → pectineal line; weak trunk flexor.
• Sartorius – ASIS → pes anserinus (superomedial tibia); femoral n.; flex, abduct, ER hip + flex knee, MR tibia (“tailor”).

Knee Extensors (Quadriceps Femoris)

• Rectus femoris – AIIS; crosses hip (flexor).
• Vastus lateralis, intermedius, medialis; all insert via quad tendon → patella → patellar lig. → tibial tuberosity.
• VM oblique fibers stabilize patella vs. lateral pull.

Medial Thigh (Adductors)

• Longus – body pubis → middle linea aspera.
• Brevis – body & inf. ramus pubis → prox. linea aspera.
• Magnus – (adductor part) inf. ramus pubis/ischium → linea aspera | (hamstring part) ischial tuberosity → adductor tubercle; dual innervation obturator (post br.) & tibial n.
• Gracilis – body/inf. ramus pubis → pes anserinus; crosses knee.
• Obturator externus – margins obturator foramen/membrane → trochanteric fossa; one of “deep six” ERs.

Femoral Triangle

• Borders: inguinal lig. (base) | sartorius (lat) | adductor longus med. border (medial).
• Floor: iliopsoas (lat) → pectineus → adductor longus.
• Contents (lat→med): femoral n. (outside sheath) | femoral a. | femoral v. | lymph (femoral canal).
• Femoral sheath – fascia from transversalis + iliopsoas; permits vessel glide under inguinal lig.; femoral branch of genitofemoral n. inside; femoral n. outside.

Adductor Canal

• Apex of triangle → adductor hiatus (magnus).
• Walls: vastus medialis (lat/anterior), adductors longus+magnus (post), sartorius (roof).
• Passage for femoral a., v. & saphenous n.

Vascular Supply

• Aorta → common iliac → internal + external iliac.
• External iliac → femoral a. (after inguinal lig.).
• Branches inside triangle: profunda femoris (deep) → medial & lateral circumflex femoral aa.
• Lateral circumflex → ascending, transverse, descending branches (knee anastomosis).
• Medial circumflex – between iliopsoas & pectineus; major supply femoral head/neck.
• Femoral → popliteal a. after adductor hiatus.
• Posterior thigh: 4 perforating branches of profunda femoris.
• Genicular anastomosis around knee: branches femoral, popliteal, anterior tibial.

Fascial Compartments

• Deep fascia lata + intramuscular septa divide thigh into anterior, medial, posterior compartments → neurovascular segregation; clinical relevance = compartment syndrome, fasciotomy.

Gluteal Region

• Boundaries: iliac crest (sup) → inf. border gluteus maximus (gluteal fold).
• Ligaments recap: sacrotuberous & sacrospinous close sciatic notches → foramina.

Gluteal Muscles

• Tensor fasciae latae – ASIS/iliac crest → ITB (Gerdy’s tubercle); sup. gluteal n.; abduct, MR, flex hip, tense ITB.
• Gluteus maximus – post. ilium/sacrum/coccyx/sacrotuberous lig. → gluteal tuberosity + ITB; inf. gluteal n.; hip extension, LR, rising/landing, stabilize knee.
• Gluteus medius & minimus – ilium (between gluteal lines) → greater trochanter; sup. gluteal n.; abduct & MR; pelvic leveling during gait.
• Injury → Trendelenburg sign (contralat. pelvic drop when standing on affected limb).
• Piriformis – ant. sacrum → sup. greater trochanter; n. to piriformis; ER & abduct flexed thigh; landmark for sciatic n. exit (88 % below).
• Obturator internus + Sup./Inf. gemelli – obturator membrane & ischium → medial greater trochanter (trochanteric fossa); n. to obturator internus or quadratus femoris; ER & abduct flexed hip.
• Quadratus femoris – lat. ischial tuberosity → quadrate tubercle (intertrochanteric crest); n. to quadratus femoris; strong ER.

Gluteal Neurovasculature

• Superior gluteal n./a. exit GSF above piriformis; supply TFL + glut. med/min.
• Inferior gluteal n./a. exit below piriformis; supply glut. maximus.
• Sciatic n. path: midway PSIS–ischial tuberosity line → midpoint IT–greater trochanter (~⅓).
• Cutaneous: superior cluneal (L1–3), medial cluneal (S1–3), inferior cluneal branches of post. femoral cutaneous (S1–3).

Entrapment Syndromes

• Piriformis syndrome – sciatic n. compression under/through muscle → buttock pain, dysesthesia radiating down leg.
• Hamstring syndrome – entrapment within hamstring origin or fibrous bands near ischial tuberosity.

Posterior Thigh (Hamstrings)

• True hamstring criteria: crosses hip & knee, tibial division innervation, origin ischial tuberosity.
• Semitendinosus – IT → pes anserinus; extend hip, flex & MR knee.
• Semimembranosus – IT → post. med. tibial condyle; same actions.
• Biceps femoris long head – IT → fibular head (split by LCL); extends hip, flexes & LR knee.
• “Wannabes”: Biceps short head (origin linea aspera; common fibular n.) & adductor magnus hamstring part (tibial n.; only hip ext).
• Blood: perforators of profunda femoris.

Popliteal Fossa

• Borders: biceps fem. (superolateral), semimen.+semiten. (superomed), gastrocnemius heads (inferior).
• Contents: popliteal a./v., tibial n., common fibular n., small saphenous v. termination, fat, lymph.
• Roof – skin & fascia w/ post. femoral cutaneous n.; floor – popliteal surface femur, capsule, popliteus.
• Sural cutaneous network: medial sural (from tibial) + lateral sural (from common fibular) → sural n. to posterolateral leg/foot.

Genicular Anastomosis

• Superior med/lat genicular aa., inferior med/lat genicular aa., descending genicular (femoral), descending branch lateral circumflex, ant. tibial recurrent.
• Ensures perfusion during knee flexion when popliteal a. kinked.

Neurologic & Sensory Summaries

• Myotomes (Netter):
• Hip flexion L1–2; extension L5–S1.
• Knee extension L3–4; flexion L5–S2.
• Ankle DF L4–5; PF S1–2.
• Foot inversion L4–5; eversion L5–S1.
• Dermatomes: spiral from L1 (inguinal) down anterior thigh (L2–4), medial leg (L4), dorsum foot (L5), lateral foot/posterior leg S1, posterior thigh S2. Considerable overlap; use autonomous zones for testing.
• Peripheral cutaneous maps: femoral, lat. femoral cutaneous, obturator, sciatic branches, etc.

Key Numbers & Formulas

• Angle of inclination normal \approx126^{\circ}; extremes <105^{\circ} (vara), >140^{\circ} (valga).
• Normal femoral anteversion 15^{\circ}-20^{\circ}.
• Hip flexion limited by capsule winds @ 10^{\circ}-20^{\circ} extension.
• Femur ≈ \tfrac14 total height.