Popliteal Artery Anatomy

Also written as Popliteal trunk.

The popliteal artery is the continuation of the femoral artery behind the knee, supplying the lower leg and foot. Its course, branches and relationships are crucial for diagnosing trauma, aneurysm and peripheral arterial disease, especially where imaging is limited.

Overview

The popliteal artery runs in the popliteal fossa from the adductor hiatus to the lower border of the popliteus muscle where it divides into the anterior and posterior tibial arteries.

• Key landmark: adductor hiatus of the femur
• Divides at the level of the tibial tuberosity

Location and structure

It lies deep in the fossa, initially superficial to the popliteal vein, then deep to it as it descends. The artery is a muscular vessel about 15 cm long.

• Length ≈ 15 cm, diameter 6–9 mm
• Surrounded by the popliteal fascia and fat

Relations

Anteriorly the artery is bordered by the popliteus muscle; posteriorly by the popliteal vein and tibial nerve. The small saphenous vein pierces the fascia near the medial head of gastrocnemius.

• Popliteal vein lies superficial early, then deep
• Tibial nerve runs medial to the artery

Blood supply

Branches include the genicular arteries (superior, middle, inferior) that form an anastomotic network around the knee, the sural arteries, and the anterior/posterior tibial arteries.

• Genicular arteries maintain knee perfusion during flexion
• Anterior tibial artery supplies the dorsum of the foot

Nerve supply

The arterial wall receives sympathetic fibers from the lumbar sympathetic chain via the hypogastric plexus; no direct somatic innervation.

• Sympathetic tone regulates vessel diameter

Function

Delivers oxygenated blood to the knee joint, posterior compartment of the leg, and foot; its pulsation is a bedside indicator of distal perfusion.

• Palpable popliteal pulse predicts intact tibial pulses

Clinical relevance and injuries

Trauma, popliteal artery aneurysm, and peripheral arterial disease (PAD) are the main threats. In low‑resource settings, delayed presentation and limited imaging increase limb‑loss risk.

• Ankle‑brachial index (ABI): Is there hemodynamic obstruction? ABI < 0.9 indicates PAD; if Doppler unavailable, use handheld Doppler or clinical pulse‑pressure assessment
• Duplex ultrasound: Is there aneurysm or stenosis? Shows flow velocity; if ultrasound unavailable, rely on palpable pulse asymmetry and bedside Doppler
• CT angiography: What is the exact anatomy before surgery? Shows branch involvement; if CT unavailable, consider plain X‑ray for fracture and clinical assessment

• Aneurysm: pulsatile mass, absent distal pulses, risk of thrombosis
• Trauma: popliteal fracture or dislocation can transect the artery
• PAD: calf claudication, cold foot, delayed capillary refill

Exam pearls

When assessing a patient with suspected popliteal pathology, start with a systematic vascular exam and then consider the most likely local causes.

• Check femoral, popliteal, posterior tibial and dorsalis pedis pulses
• Compare limb temperatures and capillary refill
• Look for a pulsatile mass in the popliteal fossa

Questions an examiner may ask

• A 45‑year‑old farmer presents with calf claudication after walking 50 m. What is the next investigative step and why? — ABI; values < 0.9 confirm PAD and guide further imaging.
• During knee replacement, the surgeon notes a pulsatile mass in the popliteal fossa. What is the most likely diagnosis and immediate management? — Popliteal artery aneurysm; obtain vascular surgery consult and arrange duplex ultrasound.
• A patient with a distal femur fracture has a weak popliteal pulse but normal femoral pulse. What does this suggest and what should you do? — Possible arterial injury; immobilise limb, call vascular team, arrange urgent imaging.
• Explain why the genicular arteries are important when the knee is flexed. — They provide collateral flow, preventing ischemia when the main popliteal lumen is compressed.
• A diabetic patient presents with a cold foot and absent dorsalis pedis pulse but a palpable popliteal pulse. What is the likely level of obstruction? — Occlusion distal to the popliteal bifurcation, likely tibial artery disease.
• Why is a CT angiogram preferred over plain X‑ray in evaluating a suspected popliteal artery injury? — CT angiogram visualises vessel lumen, detects intimal flaps and pseudo‑aneurysms, which X‑ray cannot.
• In a low‑resource clinic, how would you monitor a patient with a known popliteal aneurysm? — Serial clinical measurement of mass size, pulse assessment, and ABI; refer for surgery if rapid growth or symptoms develop.
• What drug class should be avoided in a patient with a popliteal artery aneurysm undergoing elective repair and why? — Non‑selective NSAIDs; they impair platelet function and increase bleeding risk during surgery.

When to seek help

• Absent distal pulses with a painful, swollen knee after trauma
• Rapidly expanding popliteal mass
• Severe calf pain with pallor and paresthesia (suspected acute limb ischemia)

Quick questions

Why is the popliteal pulse important in a trauma patient?

It indicates that the artery is intact; loss suggests transection or thrombosis requiring urgent vascular review.

Can a popliteal aneurysm be asymptomatic?

Yes, it may be discovered incidentally, but it carries a high risk of thrombosis and distal embolisation.

What bedside test helps when Doppler is not available?

Manual assessment of pulse strength and capillary refill, combined with a blood pressure cuff to compare systolic pressures between limbs.