Buttocks: Either of two fleshy protuberances at the lower posterior section of the trunk or HIP in humans and primate on which a person or animal sits, consisting of gluteal MUSCLES and fat.Iliac Artery: Either of two large arteries originating from the abdominal aorta; they supply blood to the pelvis, abdominal wall and legs.Pressure Ulcer: An ulceration caused by prolonged pressure on the SKIN and TISSUES when one stays in one position for a long period of time, such as lying in bed. The bony areas of the body are the most frequently affected sites which become ischemic (ISCHEMIA) under sustained and constant pressure.Iliac Aneurysm: Abnormal balloon- or sac-like dilatation in the wall of any one of the iliac arteries including the common, the internal, or the external ILIAC ARTERY.Piriformis Muscle Syndrome: A chronic PELVIC PAIN characterized by pain deep in the buttock that may radiate to posterior aspects of the leg. It is caused by the piriformis muscle compressing or irritating the SCIATIC NERVE due to trauma, hypertrophy, inflammation or anatomic variations.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.Blood Gas Monitoring, Transcutaneous: The noninvasive measurement or determination of the partial pressure (tension) of oxygen and/or carbon dioxide locally in the capillaries of a tissue by the application to the skin of a special set of electrodes. These electrodes contain photoelectric sensors capable of picking up the specific wavelengths of radiation emitted by oxygenated versus reduced hemoglobin.Pelvis: The space or compartment surrounded by the pelvic girdle (bony pelvis). It is subdivided into the greater pelvis and LESSER PELVIS. The pelvic girdle is formed by the PELVIC BONES and SACRUM.Sacroiliac Joint: The immovable joint formed by the lateral surfaces of the SACRUM and ILIUM.Thigh: The portion of the leg in humans and other animals found between the HIP and KNEE.Sacroiliitis: Inflammation of the SACROILIAC JOINT. It is characterized by lower back pain, especially upon walking, fever, UVEITIS; PSORIASIS; and decreased range of motion. Many factors are associated with and cause sacroiliitis including infection; injury to spine, lower back, and pelvis; DEGENERATIVE ARTHRITIS; and pregnancy.Acrospiroma: A rare cutaneous tumor of eccrine sweat gland origin. It is most commonly found on the extremities and is usually benign. There is no indication that heredity or external agents cause these tumors.