An aneurysm refers to a dilated segment of an artery caused by weakness and thinning of the wall. Leg aneurysms are relatively rare, but occur more commonly than arm aneurysms. Most leg aneurysms develop in the popliteal artery, which passes behind the knee before branching to supply blood to the lower leg and foot. Iliofemoral aneurysms involve the large arteries that enter the leg at its junction with the hip and are even more uncommon. Most leg aneurysms cause no symptoms, especially if small. When symptoms develop, they typically occur due to the aneurysm compressing nearby structures, or the formation of a blood clot in the dilated artery.
Because most leg aneurysms cause no symptoms, they often go unnoticed until complications develop. However, a painless pulsating mass -- which differs from a normal arterial pulse -- might come to the attention of an astute person or his doctor. A popliteal aneurysm might cause such a mass behind the knee, whereas an iliofemoral aneurysm mass would be located toward the middle of the crease at the junction of the thigh and hip.
The pulsation in the mass might feel unusual to your doctor due to slight vibration caused by turbulent blood flow in the aneurysm. Listening to the mass with a stethoscope can confirm this turbulent flow, which frequently produces a swooshing sound called a bruit.
Leg Pain and Abnormal Sensations
A leg aneurysm that compresses a nearby nerve can lead to tingling, numbness, a burning sensation or shoot leg pain. These sensations typically originate near the site of the aneurysm and radiate downward. Muscle weakness might also occur due to compression of motor nerves. Aching bone pain might occur if the aneurysm is large enough to compress nearby bones of the leg, although this is uncommon.
Leg pain might also develop if a blood clot forms within the aneurysm -- a frequent occurrence -- and limits blood supply to the area of the leg beyond the clot. This type of pain, known as ischemic pain, typically worsens with activity and abates with rest if the artery is not completely blocked. Sudden, severe leg pain might signal complete obstruction of a leg artery by an aneurysm-derived blood clot or rupture of the aneurysm, both of which require emergency medical treatment.
Swelling and Discoloration
Major arteries and veins course through the leg in close proximity. A large arterial leg aneurysm can compress nearby veins, causing pooling of blood due to partially obstructed outflow. This might lead to swelling of the leg, or edema, below the site of the aneurysm. Edema is typically most noticeable in the ankle and foot, and might cause one shoe to be unusually tight. Longstanding edema related to vein obstruction can cause reddish-brown skin discoloration of the affected leg.
With significant obstruction of arterial blood flow into a leg due to an aneurysm-related blood clot, the skin might appear unusually pale or bluish. In some people, tiny pieces of the clot in the aneurysm break off and lodge in small arteries of the feet or toes, causing localized blue or purple discoloration.
Warnings and Precautions
Most leg aneurysms cause no symptoms and come to light coincidentally. However, if you develop any signs or symptoms that might indicate a leg aneurysm, see you doctor as soon as possible. As the symptoms of a leg aneurysm are not specific, you might not have this condition. But it's important to be evaluated promptly so that appropriate treatment can begin.
Seek emergency medical care if you experience sudden, severe leg pain. This could signal complete obstruction of blood flow to your leg due to a clot or rupture of the aneurysm -- both of which might necessitate amputation if not treated immediately.
Reviewed and revised by: Tina M. St. John, M.D.