An aneurysm is a weak spot in an arterial wall that typically results in bulging or ballooning of the artery beyond its normal size or thickness. An aneurysm can throw off blood clots and cause arteries to burst with uncontrolled bleeding. An aneurysm can occur just about anywhere in the body including the extremities. The most common sites for aneurysms to develop are the abdominal aorta, brain, back of the knee, intestine, or spleen. Ruptured aneurysms can cause internal bleeding, stroke and even death. Aneurysms may have no symptoms until they rupture.