Blood Supply and Venous Drainage

The Continuous Arterial Pathway

External iliac artery → femoral artery → popliteal artery → anterior tibial artery + posterior tibial artery (via the tibiofibular trunk, which also gives the fibular artery) → dorsalis pedis (from anterior tibial) + medial/lateral plantar arteries (from posterior tibial) → plantar arch → digital arteries.

External iliac artery: becomes the femoral artery at the inguinal ligament (midinguinal point).
Femoral artery: descends through the femoral triangle and adductor canal, gives off the profunda femoris; becomes the popliteal artery at the adductor hiatus.
Profunda femoris (deep femoral) artery: largest branch of the femoral artery, arises just distal to the inguinal ligament; gives the medial and lateral circumflex femoral arteries and 3–4 perforating arteries supplying the posterior thigh muscles.
Popliteal artery: deepest structure in the popliteal fossa; gives genicular branches; divides into anterior and posterior tibial arteries at the lower border of popliteus.
Anterior tibial artery: passes through the interosseous membrane into the anterior compartment; becomes the dorsalis pedis artery at the ankle.
Posterior tibial artery: descends in the posterior compartment; gives off the fibular (peroneal) artery; passes posterior to the medial malleolus, divides into medial and lateral plantar arteries.
Dorsalis pedis artery: palpable on the dorsum of the foot, lateral to extensor hallucis longus tendon; gives a deep plantar branch that completes the plantar arch.
Plantar arch: formed predominantly by the lateral plantar artery, completed by the deep plantar branch of dorsalis pedis; gives rise to plantar metatarsal and digital arteries.

Major Branches (Summary)

Level	Key Branches
Femoral artery	Superficial epigastric, superficial circumflex iliac, superficial/deep external pudendal, profunda femoris
Profunda femoris	Medial circumflex femoral, lateral circumflex femoral, perforating arteries (×3-4)
Popliteal artery	Superior medial/lateral genicular, middle genicular, inferior medial/lateral genicular, sural arteries
Posterior tibial	Circumflex fibular, fibular (peroneal) artery, medial/lateral plantar arteries
Anterior tibial	Posterior/anterior tibial recurrent, medial/lateral malleolar, becomes dorsalis pedis

Important Relationships

Femoral artery is the most lateral of the three femoral triangle contents within the sheath (mnemonic NAVEL).
Popliteal artery lies deepest in the popliteal fossa, directly applied to the posterior femur/knee capsule, vulnerable in posterior knee dislocation and supracondylar femoral fracture.
Posterior tibial artery accompanies the tibial nerve through the tarsal tunnel.

Anastomotic Networks

Trochanteric anastomosis:

Around the hip, formed by the medial and lateral circumflex femoral arteries (from profunda femoris), the superior gluteal artery, and the inferior gluteal artery (both from the internal iliac artery).
Supplies the femoral head and neck region (via retinacular branches, predominantly from the medial circumflex femoral artery) and provides collateral flow around the hip joint.

Cruciate anastomosis:

Just below the trochanteric anastomosis, around the upper femoral shaft, formed by the medial circumflex femoral artery, lateral circumflex femoral artery, first perforating artery (from profunda femoris), and the inferior gluteal artery.
Provides collateral circulation for the proximal thigh, particularly relevant if the femoral artery is occluded or ligated above the origin of profunda femoris, flow can be maintained retrograde through this network.

Genicular anastomosis:

Around the knee, formed by five genicular branches of the popliteal artery (superior medial, superior lateral, middle, inferior medial, inferior lateral), the descending genicular artery (from the femoral artery, before the adductor hiatus), the descending branch of the lateral circumflex femoral artery, the circumflex fibular artery, and the anterior/posterior tibial recurrent arteries.
Provides critical collateral circulation around the knee, especially relevant if the popliteal artery is injured or must be ligated (e.g., in trauma or aneurysm repair), though (similar to the elbow) this collateral network is often insufficient to fully prevent distal ischaemia if the popliteal artery is acutely and completely occluded, given the popliteal artery's role as a relatively "end-artery" for much of the leg.

Malleolar anastomoses:

Medial malleolar anastomosis: branches of the anterior tibial and posterior tibial arteries around the medial malleolus.
Lateral malleolar anastomosis: branches of the anterior tibial and fibular arteries around the lateral malleolus.
Provide collateral flow around the ankle.

Plantar anastomoses:

The plantar arch itself represents the major anastomotic connection between the posterior tibial (lateral plantar artery) and anterior tibial (via dorsalis pedis' deep plantar branch) systems in the foot.

Superficial Veins

Vein	Origin	Course	Termination
Great saphenous vein	Medial end of the dorsal venous arch of the foot	Ascends anterior to the medial malleolus, up the medial leg and thigh (longest vein in the body)	Femoral vein, at the saphenofemoral junction (through the saphenous opening/fossa ovalis)
Small saphenous vein	Lateral end of the dorsal venous arch of the foot	Ascends posterior to the lateral malleolus, up the posterior calf	Popliteal vein, at the saphenopopliteal junction

Deep Veins

Anterior tibial veins, posterior tibial veins, fibular veins: paired venae comitantes accompanying the respective arteries, converge to form the popliteal vein.
Popliteal vein: receives the small saphenous vein; continues as the femoral vein at the adductor hiatus.
Femoral vein: ascends through the adductor canal and femoral triangle (medial to the femoral artery), receives the great saphenous vein and profunda femoris vein; becomes the external iliac vein at the inguinal ligament.

Perforating Veins and Valves

Perforating veins connect the superficial system to the deep system at multiple levels (classically named groups exist along the medial leg and thigh, e.g., Cockett's and Boyd's perforators, though naming conventions vary by source).
Normal valves within both the superficial, deep, and perforating veins direct flow unidirectionally toward the heart and from superficial to deep: the calf muscle pump (contraction of the surrounding leg muscles, especially gastrocnemius/soleus, compresses the deep veins) is the primary mechanism propelling venous return against gravity in the erect position.
Valve incompetence (primary, or secondary to previous DVT) allows retrograde flow and venous hypertension, the underlying mechanism of varicose veins and chronic venous insufficiency.

Applied Anatomy

Varicose veins:

Dilated, tortuous superficial veins, most often affecting the great saphenous vein and its tributaries, resulting from valvular incompetence (primary/idiopathic, or secondary to previous DVT, pregnancy, prolonged standing, or family history).
Saphenofemoral junction incompetence is a common underlying cause, allowing reflux down the entire great saphenous vein.

DVT anatomy:

Deep vein thrombosis most commonly originates in the calf deep veins (soleal sinuses are a classic origin site, given relative stasis) and can propagate proximally into the popliteal and femoral veins.
Risk factors follow Virchow's triad (stasis, hypercoagulability, endothelial injury), prolonged immobility, surgery, malignancy, pregnancy, and inherited thrombophilias are classic contributors.
Clinical concern is proximal propagation (above the knee) increasing the risk of pulmonary embolism, given the larger vessel calibre and higher clot burden potential.

Venous cutdown landmarks:

The great saphenous vein at the ankle (anterior to the medial malleolus) is a classic, reliable venous cutdown site for emergency vascular access, given its consistent anatomical position even when collapsed or difficult to visualise/palpate (e.g., in hypovolaemic shock).