Intracranial Arterial Diseases: Pathological conditions involving ARTERIES in the skull, such as arteries supplying the CEREBRUM, the CEREBELLUM, the BRAIN STEM, and associated structures. They include atherosclerotic, congenital, traumatic, infectious, inflammatory, and other pathological processes.Peripheral Arterial Disease: Lack of perfusion in the EXTREMITIES resulting from atherosclerosis. It is characterized by INTERMITTENT CLAUDICATION, and an ANKLE BRACHIAL INDEX of 0.9 or less.Peripheral Vascular Diseases: Pathological processes involving any one of the BLOOD VESSELS in the vasculature outside the HEART.Intermittent Claudication: A symptom complex characterized by pain and weakness in SKELETAL MUSCLE group associated with exercise, such as leg pain and weakness brought on by walking. Such muscle limpness disappears after a brief rest and is often relates to arterial STENOSIS; muscle ISCHEMIA; and accumulation of LACTATE.Ankle Brachial Index: Comparison of the BLOOD PRESSURE between the BRACHIAL ARTERY and the POSTERIOR TIBIAL ARTERY. It is a predictor of PERIPHERAL ARTERIAL DISEASE.Ankle: The region of the lower limb between the FOOT and the LEG.Arterial Occlusive Diseases: Pathological processes which result in the partial or complete obstruction of ARTERIES. They are characterized by greatly reduced or absence of blood flow through these vessels. They are also known as arterial insufficiency.Lower Extremity: The region of the lower limb in animals, extending from the gluteal region to the FOOT, and including the BUTTOCKS; HIP; and LEG.Leg: The inferior part of the lower extremity between the KNEE and the ANKLE.Brachial Artery: The continuation of the axillary artery; it branches into the radial and ulnar arteries.Tibial Arteries: The anterior and posterior arteries created at the bifurcation of the popliteal artery. The anterior tibial artery begins at the lower border of the popliteus muscle and lies along the tibia at the distal part of the leg to surface superficially anterior to the ankle joint. Its branches are distributed throughout the leg, ankle, and foot. The posterior tibial artery begins at the lower border of the popliteus muscle, lies behind the tibia in the lower part of its course, and is found situated between the medial malleolus and the medial process of the calcaneal tuberosity. Its branches are distributed throughout the leg and foot.Ischemia: A hypoperfusion of the BLOOD through an organ or tissue caused by a PATHOLOGIC CONSTRICTION or obstruction of its BLOOD VESSELS, or an absence of BLOOD CIRCULATION.Walking: An activity in which the body advances at a slow to moderate pace by moving the feet in a coordinated fashion. This includes recreational walking, walking for fitness, and competitive race-walking.Amputation: The removal of a limb or other appendage or outgrowth of the body. (Dorland, 28th ed)Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.