The popliteal artery is located deeper, adjacent to the popliteal surface of the femur and the posterior part of the knee capsule. It runs obliquely along the outer edge of the semitendinosus muscle to the level of the condylar fossa of the femur at the middle of the back of the knee, and then vertically down to the lower edge of the popliteal muscle, where it divides into the anterior tibial artery and the posterior tibial artery. The former enters the anterior calf via the superior border of the interosseous membrane, and the latter enters the posterior calf via the deep surface of the tendon arch of the piriformis muscle. In addition to the muscular branches of this artery, which are distributed to the neighboring muscles, there are five articular branches, i.e., the medial and lateral suprapatellar arteries, the middle patellar artery, and the medial and lateral infrapatellar arteries, which are involved in forming the arterial network of the knee joint. The upper popliteal artery is closely related to the popliteal surface of the femur. Etiology: The popliteal artery pulsation is diminished or absent when popliteal artery aneurysm occurs, and the popliteal artery may also be injured when a supracondylar fracture of the femur occurs. DIAGNOSIS: Weakness or absence of popliteal artery pulsation is recognized when popliteal artery pulsation is absent or weak at the popliteal artery site. Differentials: A variety of disorders can present with symptoms of decreased or absent popliteal artery pulsation: 1. Popliteal aneurysm: Smaller uncomplicated popliteal aneurysms are often asymptomatic, but sooner or later complications and symptoms develop 68% of conservatively observed cases by Szilagyi et al. within 5 years. 26 popliteal aneurysms were followed by Vermilion et al. with a mean follow up time of 3 years, 31% developed limb-threatening complications. threatening complications. According to the manifestations of limb ischemia and compression symptoms, combined with physical signs such as limb coldness and numbness, weakened or absent pulse, pulsatile popliteal fossa swelling, as well as egg-shell-shaped calcified shadows on X-ray radiographs, ultrasound, CT arteriography, and other examinations, the diagnosis is not difficult to establish. If limb ischemia occurs, there may be signs such as pale skin, limb ulceration or gangrene, weakening or disappearance of popliteal artery pulsation, and coldness of the limb. If popliteal artery aneurysm is suspected, the opposite side of the limb should also be examined to confirm whether there is a combination of other parts of the aneurysm. 2.Acute arterial embolism: acute arterial embolism without compensation of collateral circulation, the condition progresses rapidly. The typical symptoms of acute arterial embolism are pain, pallor, coldness, numbness, dyskinesia, and weakened and disappeared arterial pulsations. The severity of symptoms depends on the location and degree of embolism, the amount of secondary thrombosis, whether there is previous atherosclerotic disease causing arterial stenosis, and the condition of collateral circulation. The diagnosis is generally confirmed in cases of sudden onset of limb pain with acute arterial ischemia and disappearance of the corresponding arterial pulsation.