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AN20.1-10 | General Features, Joints, radiographs & surface marking (Lower Limb) — Part 2

Venous Drainage & Varicose Veins

Superficial Veins
- Great (Long) Saphenous Vein (GSV): Begins at the medial end of the dorsal venous arch of the foot → passes anterior to medial malleolus → up the medial side of the leg → passes posterior to medial condyle of femur → enters the femoral vein at the saphenous opening (4 cm below and lateral to pubic tubercle) via the cribriform fascia. Contains 12-15 valves.
- Small (Short) Saphenous Vein (SSV): Begins at lateral end of dorsal venous arch → passes posterior to lateral malleolus → up the posterior midline of the leg → pierces deep fascia to enter the popliteal vein.

Perforating Veins: Connect superficial to deep venous systems. Valves normally allow flow from superficial → deep only.

Varicose Veins (AN20.5)
- Definition: Dilated, tortuous superficial veins due to incompetent valves
- Anatomical basis: Valve incompetence (especially at saphenofemoral junction for GSV, or in perforating veins) → blood refluxes from deep to superficial → increased superficial venous pressure → vessel wall dilation and elongation → tortuous varicosities
- Venous ulcer location: Above medial malleolus (gaiter area) — maximal hydrostatic pressure + poor tissue perfusion from chronic venous hypertension → skin breakdown
- DVT (AN20.5): Virchow's triad — Stasis (prolonged immobility) + Endothelial damage + Hypercoagulability. Soleal sinuses are the primary DVT initiation site. Popliteal and femoral DVT can propagate to iliac veins. Risk of pulmonary embolism.
- Indian context: Prolonged squatting (Asian posture) compresses popliteal veins → DVT risk in susceptible individuals

Lymphatic Drainage & Inguinal Lymphadenopathy

Lymphatic Drainage of the Lower Limb (AN20.3 & AN20.4)

Superficial inguinal nodes (in the femoral triangle):
- Horizontal group: Along the inguinal ligament → drain the lower anterior abdominal wall, perineum, external genitalia, gluteal region, anal canal
- Vertical group: Along the great saphenous vein → drain the entire lower limb superficially

Deep inguinal nodes: Along the femoral vein, medial to it → drain the deep structures of the lower limb and receive efferents from superficial inguinal nodes. Cloquet's node (Rosenmuller's node) = highest deep inguinal node, lies in the femoral canal.

Clinical — Inguinal Lymphadenopathy (AN20.4):
- Infected toe/foot/leg → vertical superficial inguinal nodes
- External genitalia/anal infection → horizontal superficial inguinal nodes
- Scrotal carcinoma → superficial inguinal nodes (NOT external iliac — because scrotum drains to inguinal nodes, NOT para-aortic)
- Testicular carcinoma → para-aortic nodes (because testes develop in abdomen and drain to lumbar/para-aortic nodes, NOT inguinal)
- Penile carcinoma → inguinal nodes
- Metastatic nodes: Hard, non-tender, fixed. Primary can be anywhere in the drainage territory.

Exam trap: Don't confuse scrotal lymphatics (→ inguinal) with testicular lymphatics (→ para-aortic).

Radiographs of the Lower Limb — What to Identify

AP Radiograph of the Hip (AN20.6)
Identify: Head of femur (spherical, in acetabulum), neck of femur (angle of inclination ~126°), greater trochanter, lesser trochanter (on posteromedial aspect, visible on AP), intertrochanteric line/crest, femoral shaft.
Shenton's line: Smooth arc from inferior border of superior pubic ramus to inferior border of femoral neck — disrupted in fracture/dislocation of hip.
Neck-shaft angle: Normal ~126° (coxa vara <120°, coxa valga >135°)

AP Radiograph of the Knee
Identify: Medial and lateral femoral condyles, medial and lateral tibial condyles (plateaux), tibial spine (intercondylar eminence), head of fibula, joint space (medial 3-4mm, lateral 3-4mm), patella (on AP partially superimposed), fabella (sesamoid in gastrocnemius — normal variant).

AP + Lateral Radiograph of the Ankle
Identify on AP: Tibial plafond, medial malleolus, lateral malleolus (fibula tip), talar trochlea (dome), ankle mortise (uniform 3mm joint space all around — asymmetry indicates instability or fracture).
Identify on Lateral: Tibia, fibula (superimposed posteriorly), talus, calcaneus, navicular, cuboid, 5th metatarsal base (avulsion fracture site — do not confuse with accessory ossicle).

AP Radiograph of the Foot
Identify: All five metatarsals, phalanges (proximal, middle, distal), tarsals (medial, intermediate, lateral cuneiforms; navicular; cuboid). Check Lisfranc alignment: medial border of 2nd metatarsal should align with medial border of middle cuneiform.

Key measurements:
- Bohler's angle (on lateral calcaneus X-ray): Normal 20-40°. Reduced in calcaneal fractures (falls from height).
- Hilgenreiner's line (hip): horizontal through both triradiate cartilages — used for DDH assessment in infants.