Popliteal artery !

The popliteal artery is the main artery behind the knee, lying deepest in the hollow there; it carries blood to the leg and foot.

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What it is

The main artery behind the knee, continuing from the femoral artery.

What it does

Carries blood to the lower leg and foot.

Key facts

Origin: Continuation of femoral artery at adductor hiatus
Branches: Five genicular arteries, sural arteries; ends at lower border of popliteus as anterior and posterior tibial
Supplies: Knee joint and calf muscles; leg and foot via terminal branches; deepest structure in popliteal fossa

Relations

Course: From the adductor hiatus it runs down and slightly laterally through the popliteal fossa, passes under the fibrous arch of the soleus and divides at the lower border of the popliteus into the anterior tibial artery and posterior tibial artery
In front: Popliteal surface of the femur (with a fat pad between), the knee capsule and oblique popliteal ligament, then the fascia over the popliteus
Behind: The popliteal vein, bound to it in a common sheath, and the tibial nerve behind that; both cross behind the artery from lateral to medial on the way down
Medial: The semimembranosus above, the medial head of gastrocnemius below
Lateral: The biceps femoris and lateral femoral condyle above; the lateral head of gastrocnemius and the plantaris below

How to find it

The pulse is deep and easy to miss. With the person supine and the knee partly bent to slacken the popliteal fascia, the examiner wraps both hands around the knee and presses the fingertips into the centre of the fossa against the back of the tibia. An unusually wide, easily felt pulse suggests an aneurysm.

Examination

Ankle–brachial index with a handheld Doppler after any knee dislocation, compared with the other leg; a value under about 0.9 leads to CT angiography
Ankle pulses with the knee straight during forced plantar flexion: pulses that fade suggest popliteal entrapment

On imaging

Duplex ultrasound measures an aneurysm and the clot inside it. CT angiography is the quick study after knee trauma and shows the run-off to the foot; catheter angiography allows treatment in the same session. Duplex during plantar flexion, CT or MRI shows entrapment.

Common problems

Damage in a knee dislocation; this is an emergency.
Aneurysm (a bulge in the artery wall), more common in older adults.
Rarely, compression by muscles in young athletes (entrapment).

How it is diagnosed

Checking the pulses in the foot, the ankle-brachial index, ultrasound, CT angiography.

Treatment

Injury: urgent surgical repair.
Aneurysm or blockage: monitoring, a bypass or an endovascular repair.

Clinical notes

Acute ischemia (trauma or embolus) shows the 6 Ps: pain, pallor, pulselessness, paresthesia, paralysis and poikilothermia; nerve and muscle begin to suffer lasting damage within about 6 hours without flow
Popliteal aneurysm: its main danger is sudden thrombosis or emboli that block the leg arteries, more than rupture
Popliteal artery entrapment: an abnormal course around the medial head of gastrocnemius squeezes it in young athletes; calf claudication, with ankle pulses that fade on forced plantar flexion
In knee replacement it lies just behind the posterior capsule, at risk from saws and retractors
When flow is restored after a long ischaemia, swelling of the leg compartments can cause compartment syndrome

Anatomical variants

In a large angiographic series (1,242 limbs) about 89% had the usual branching; hypoplastic or absent posterior tibial artery in about 5%, with the fibular artery supplying the sole
Hypoplastic anterior tibial artery about 1.7%; true trifurcation about 1.5%; high origin of the anterior tibial artery (at or above the knee joint) about 1.2%
When one limb has a variant, the other has one too in about 28%

Development

Its deep segment comes from the embryonic axial artery. Entrapment results from an abnormal relationship between the developing artery and the medial head of gastrocnemius as that muscle migrates.

Test yourself

Think of the answer, then tap the question to see it.

Which is the deepest of the main structures in the popliteal fossa?

The popliteal artery, lying against the femur and knee capsule; the popliteal vein is superficial to it and the tibial nerve most superficial.

Where does the popliteal artery end, and into which branches?

At the lower border of the popliteus, into the anterior and posterior tibial arteries.

Why does every dislocated knee need a vascular check?

The popliteal artery is fixed at the adductor hiatus and the soleus arch, so a knee dislocation stretches or tears it; pulses and ankle–brachial index are checked even after reduction.

What is the most common peripheral artery aneurysm, and what is its main danger?

Popliteal aneurysm, often bilateral and with an abdominal aortic aneurysm; its danger is thrombosis or emboli rather than rupture.

What are the 6 Ps of acute limb ischemia?

Pain, pallor, pulselessness, paresthesia, paralysis and poikilothermia.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): arteria poplitea TA2 4699
Official Spanish (DeCS): Arteria poplítea DeCS D011150
English (TA2): Popliteal artery

Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Bony Pelvis and Lower Limb: Popliteal Artery; 20.5 Circulatory Pathways (OpenStax (Rice University), 2022) · adapted, CC BY 4.0; Anatomía humana (4.ª ed.), tomo 1, cap. 67: Arterias del miembro inferior.

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Representative model, for educational purposes only.

Popliteal artery highlighted on the Durgical 3D model