A popliteal Artery Aneurysm (PAA) is an abnormal bulging or dilation of the popliteal artery, which runs behind the knee. It is the most common peripheral arterial aneurysm and accounts for nearly 70% of all peripheral aneurysms.
While it may remain silent for a long time, a PAA can lead to severe complications such as blood clots, limb ischemia, or even limb loss if left untreated. Early diagnosis and proper management are vital to prevent disability and preserve limb function.
The popliteal artery is a continuation of the femoral artery, located behind the knee joint in the popliteal fossa. It supplies blood to the lower leg and foot through its branches—the anterior tibial, posterior tibial, and peroneal arteries.
An aneurysm forms when the arterial wall weakens and balloons outward. Because of the artery’s location and constant movement with knee flexion and extension, the popliteal artery is prone to stress, making aneurysms more likely.
Unlike abdominal aortic aneurysms, which mainly risk rupture, the primary concern with PAAs is thrombosis (clot formation) and embolization (clot fragments traveling downstream), which can block blood flow to the leg.
Several factors contribute to the development of a popliteal artery aneurysm:
Atherosclerosis: The leading cause, weakening the arterial wall over time.
Age: Most cases occur in men over 60 years.
Gender: Males are more frequently affected than females.
Smoking: Increases both formation and progression risk.
Hypertension: High blood pressure stresses arterial walls.
Connective tissue disorders: Rarely, conditions like Marfan or Ehlers-Danlos syndrome can predispose individuals.
Family history: Aneurysms may cluster in families, often associated with abdominal aortic aneurysms.
Many patients remain asymptomatic, with the aneurysm discovered during imaging for another reason. However, when symptoms occur, they often relate to clot formation or pressure effects.
Typical features include:
Palpable pulsating mass behind the knee.
Leg pain or discomfort, especially during activity.
Swelling around the knee or calf.
Numbness, tingling, or weakness in the leg due to nerve compression.
Acute limb ischemia if the aneurysm clots or embolizes—manifesting as sudden severe pain, coldness, pallor, and absent pulses.
Bilateral involvement is common—about 50% of patients with one PAA also have one in the opposite leg.
Diagnosis begins with a thorough clinical evaluation followed by imaging studies.
Physical examination: May reveal a pulsatile swelling behind the knee.
Duplex ultrasound: First-line, non-invasive test to confirm aneurysm and assess blood flow.
CT angiography (CTA): Provides detailed 3D images of aneurysm size, extent, and relation to branches.
MR angiography (MRA): Useful for patients with kidney impairment or contrast allergy.
Conventional angiography: Rarely used now, but helpful in complex cases where intervention is planned.
Screening for abdominal aortic aneurysms is also recommended, since PAAs are frequently associated.
The management approach depends on aneurysm size, symptoms, and risk factors.
Small, asymptomatic aneurysms (<2 cm): May be monitored with regular ultrasound.
Risk factor modification: Stopping smoking, controlling blood pressure and cholesterol.
Medications: Antiplatelet drugs (e.g., aspirin) or anticoagulants in selected cases to reduce clot risk.
Indications for intervention include:
Symptomatic aneurysms.
Asymptomatic aneurysms ≥2 cm in size.
Evidence of thrombus, embolization, or rapid enlargement.
Options include:
Open surgical repair: The aneurysm is bypassed using a vein graft (usually the great saphenous vein) or a synthetic graft. The diseased segment may be excluded or ligated.
Endovascular repair: A minimally invasive approach where a stent graft is inserted through the artery to exclude the aneurysm and maintain flow. This option is generally preferred in high-risk surgical patients.
General or regional anesthesia is given.
An incision is made above and below the knee to expose the artery.
The aneurysm is excluded (ligated at both ends) to prevent blood flow into it.
A bypass graft, typically the patient’s own vein, is connected above and below the aneurysm to restore circulation.
Incisions are closed and circulation is reassessed.
Performed under local or regional anesthesia.
A catheter is introduced via the femoral artery.
A stent graft is guided under X-ray into the popliteal artery and deployed across the aneurysm.
The stent reinforces the artery, sealing off the aneurysm.
Endovascular repair offers faster recovery but may not be suitable for all due to the popliteal artery’s mobility and bending.
Recovery varies depending on treatment type.
Hospital stay: 2–3 days after endovascular repair, 5–7 days after open surgery.
Pain management and wound care: Essential for healing.
Mobility: Early ambulation is encouraged, but strenuous activity should be avoided for weeks.
Medications: Antiplatelet therapy (e.g., aspirin, clopidogrel) and risk factor control.
Follow-up imaging: Duplex ultrasound or CT scans are performed periodically to check graft function and aneurysm exclusion.
Potential complications include:
Thrombosis or graft occlusion: Can cause acute limb ischemia.
Infection: Particularly with synthetic grafts.
Bleeding or hematoma.
Nerve injury around the knee.
Endoleak or stent migration (specific to endovascular repair).
Limb loss: Rare if diagnosed and treated early, but possible in delayed cases.
You should seek medical evaluation if you experience:
A pulsating lump behind the knee.
Persistent leg pain, swelling, or numbness.
Sudden onset of coldness, discoloration, or severe pain in the leg (medical emergency).
People with known aneurysms elsewhere, such as an abdominal aortic aneurysm, should be screened for PAAs.
A popliteal artery aneurysm is a serious vascular condition that may remain silent until complications arise. Early detection through imaging, proper risk factor management, and timely surgical or endovascular intervention are crucial for preserving limb health and preventing life-threatening outcomes.
If you have risk factors or notice unusual swelling or pulsation behind the knee, consult a vascular specialist promptly for evaluation and guidance.
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