--- title: Popliteal artery aneurysm description: What a popliteal artery aneurysm is, why it develops, how it is found, which treatment approaches clinical guidelines describe and when to call an ambulance. type: disease aliases: - PAA - popliteal aneurysm - aneurysm of the popliteal artery - aneurysm behind the knee sources: - tier: guideline org: minzdrav-rf title: Острая ишемия конечностей year: 2025 url: https://cr.minzdrav.gov.ru/view-cr/1006_1 - tier: guideline org: esc title: 2024 ESC Guidelines for the management of peripheral arterial and aortic diseases year: 2024 doi: 10.1093/eurheartj/ehae179 url: https://doi.org/10.1093/eurheartj/ehae179 - tier: guideline org: nice title: 'Endovascular stent-grafting of popliteal aneurysms (HTG259, formerly IPG390)' year: 2011 url: https://www.nice.org.uk/guidance/htg259 - tier: guideline org: aha-acc title: '2024 ACC/AHA/AACVPR/APMA/ABC/SCAI/SVM/SVN/SVS/SIR/VESS Guideline for the Management of Lower Extremity Peripheral Artery Disease: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines' year: 2024 doi: 10.1161/CIR.0000000000001251 url: https://doi.org/10.1161/CIR.0000000000001251 - tier: reference org: msd-manuals title: Peripheral Artery Aneurysms (MSD Manual Professional Version) year: 2025 url: https://www.msdmanuals.com/professional/cardiovascular-disorders/peripheral-artery-disorders/peripheral-artery-aneurysms sources_checked: 2026-10-14 review: null --- A popliteal artery aneurysm is an abnormal widening of this artery caused by weakening of its wall. It is the most common aneurysm of the peripheral arteries: according to the MSD Manual, about 80% of such aneurysms are in the popliteal artery. Usually it causes no symptoms. Rupture is relatively rare, but a blood clot can form in the aneurysm: it either blocks the aneurysm itself or breaks off and blocks the arteries further down. This causes [acute limb ischaemia](../acute-limb-ischemia/), which is an emergency.

The diagram shows the leg from the side. The femoral artery continues as the popliteal artery, which runs at the level of the knee; below it, blood flows through the lower leg arteries to the foot.

In an aneurysm, a segment of the popliteal artery is widened; on examination the doctor may be able to feel an enlarged, pulsating artery. A blood clot can form in the aneurysm: it blocks the aneurysm or is carried with the blood into the lower leg arteries, and acute ischaemia of the leg develops.

## Why it happens The wall of the artery weakens, and the artery widens. The MSD Manual names atherosclerosis, injury (for example, in popliteal artery entrapment syndrome) and infection as common causes of peripheral artery aneurysms. Narrowing of the leg arteries in atherosclerosis is covered in the article on [peripheral artery disease of the legs](../peripheral-artery-disease/). These aneurysms are much more common in men than in women, and on average they are found in people in their 60s. The aneurysm is often present in both legs: in half of cases according to the Russian Ministry of Health guideline, and in more than half according to MSD. The same person often also has an [abdominal aortic aneurysm](../abdominal-aortic-aneurysm/) or aneurysms of other arteries. MSD defines peripheral artery aneurysms as abnormal dilations of the peripheral arteries caused by weakening of the arterial wall; about 80% are popliteal, and most of the rest are iliofemoral. NICE also describes popliteal aneurysms as the most common peripheral aneurysms. According to MSD, the male to female ratio is at least 6:1. Russian Ministry of Health guideline: patients with a popliteal artery aneurysm (PAA) often have aneurysms of the contralateral popliteal artery, the aorta and other vessels, and they are at increased risk of developing a new aneurysm. ## Symptoms Most often, when the aneurysm is found, it causes no symptoms. It is dangerous because of its complications: thrombosis, a clot breaking off (embolism) and, less often, rupture. These complications often lead to acute ischaemia of the leg: the leg hurts, becomes cold and pale, there is numbness or tingling, and the pulse in the leg may not be felt. Russian Ministry of Health guideline: a PAA can cause acute limb ischaemia through thrombosis or distal embolism involving up to three lower leg arteries; thrombosis more often leads to severe ischaemia because of rapid occlusion of the distal vessels. According to a systematic review cited in this guideline, the risk of amputation in such ischaemia is 14.1%. Among all causes of acute limb ischaemia, thrombosis of arterial aneurysms (usually of the popliteal artery) is fairly rare; ACC/AHA also include thromboembolism from an aneurysm, for example a popliteal one, in their list of causes. According to MSD, rupture is relatively infrequent. ## How it is diagnosed A doctor may suspect an aneurysm on examination when they feel an enlarged, pulsating artery. The diagnosis is confirmed by imaging: an ultrasound scan of the blood vessels (duplex ultrasound), CT angiography or MR angiography. The European (ESC) guideline suggests that doctors consider an ultrasound scan of the femoral and popliteal arteries in people with an abdominal aortic aneurysm, to look for aneurysms there too. ESC 2024: in patients with AAA, screening for femoro-popliteal aneurysms with duplex ultrasound should be considered (IIa C), including before AAA repair (IIa B). Russian Ministry of Health guideline: PAA is often diagnosed clinically (a palpable pulsatile mass), and duplex ultrasound or CT angiography is used for confirmation; patency of the tibial arteries is key to the choice of treatment because it determines the success of bypass. ## How it is treated According to NICE, treatment is expected to exclude the aneurysm from the circulation, prevent thrombosis, clots breaking off and rupture, and save the leg. According to the MSD Manual, surgery for an aneurysm of the leg arteries is planned in advance (elective); it is recommended for any popliteal artery aneurysm that causes symptoms, and for one without symptoms if its diameter is 2 cm or more. Usually this is an open operation, a bypass, in which blood is routed around the aneurysm. Another option is endovascular: a stent-graft (a tube-shaped prosthesis) is passed through the femoral artery in the groin; it lines the aneurysm from the inside and excludes it from the circulation. The sources differ in how they assess the stent-graft. The NICE guidance (2011), which is still current, calls the evidence on its efficacy inadequate because it was only short-term. The Russian Ministry of Health guideline on acute limb ischaemia (2025) calls bypass with the patient's own vein the standard and the stent-graft a full alternative to it. According to NICE, patients for stent-grafting are selected by a team of specialists that includes a vascular surgeon and an interventional radiologist. The doctor chooses the treatment. If the aneurysm has already clotted and caused acute ischaemia, blood flow is restored urgently; sometimes, before or during surgery, a clot-dissolving medicine is given through a catheter directly into the artery to open the lower leg arteries for a bypass. The Russian Ministry of Health guideline advises regular ultrasound checks of the arteries of both legs and of the aorta after surgery for a clotted aneurysm. Even an aneurysm that has been excluded from the circulation can widen again over time, and new aneurysms can appear in the other leg, the aorta and other arteries. The doctor decides which medicines are needed after surgery. MSD: the risk of rupture of extremity aneurysms is low but increases with diameter above 2 cm; repair is indicated for all symptomatic popliteal aneurysms and for asymptomatic ones ≥ 2 cm in diameter. The Russian Ministry of Health guideline and NICE give no diameter threshold. The Russian Ministry of Health guideline deals with PAA that has already caused acute ischaemia: in thrombosed PAA, the saphenous vein is recommended as the bypass conduit (level of evidence 2, grade of recommendation B); autologous vein bypass remains the standard and is superior to synthetic grafts in patency at one year. The same guideline recommends pre- or intraoperative local endovascular transarterial thrombolysis to improve run-off (level of evidence 3, grade of recommendation C); its aim is not to open the whole lumen, which increases the risk of distal embolism, but to restore patency of the tibial arteries for possible bypass. NICE HTG259 (formerly IPG390, 2011): evidence on safety is limited in quantity but shows no major safety concerns; evidence on efficacy is inadequate because it is limited to the short term, so the procedure should only be used with special arrangements for clinical governance, consent and audit or research; patient selection is carried out by a multidisciplinary team including a vascular surgeon and an interventional radiologist. Follow-up (Russian Ministry of Health guideline): after open or endovascular treatment of a thrombosed PAA, regular duplex ultrasound is recommended of the lower limb arteries on both sides, and of the aorta, iliac and femoral arteries; after endovascular repair or open repair via a medial approach, exclusion of the aneurysm sac should be checked, because late sac expansion is common: in 33% of cases after a mean of seven years of follow-up. According to the Russian guideline, there have been no dedicated studies of drug therapy after surgery for thrombosed PAA; medicines after surgery are chosen by the treating doctor. ## When to call an ambulance The aneurysm itself usually does not need emergency care: surgery for it is, as a rule, planned in advance. But its main complication, acute ischaemia of the leg, is an emergency: it must be recognised and treated quickly to save the leg. Call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK) straight away if a leg suddenly becomes painful, cold and pale, numb or tingling, or weak and hard to move. The signs are described in more detail in the article on [acute limb ischaemia](../acute-limb-ischemia/). As with any heart or blood vessel condition, call an ambulance for fainting, chest pain or severe shortness of breath: this is the site's general safety rule, repeated at the bottom of every page.