thigh

The thigh is the region of the lower limb between the hip joint and the knee. It contains the femur, the body's longest bone, and a group of muscles organized into anterior, medial, and posterior compartments. The thigh plays a central role in weight bearing, locomotion, and stabilization of the hip and knee joints.

Muscles: Anterior compartment includes the quadriceps femoris group (rectus femoris, vastus medialis, vastus lateralis, vastus intermedius) and sartorius, with hip flexors such as iliopsoas; these muscles extend the knee and assist hip flexion. Medial compartment houses the adductor group (adductor longus, adductor brevis, adductor magnus, gracilis) and pectineus, responsible for thigh adduction. Posterior compartment contains the hamstrings (biceps femoris, semitendinosus, semimembranosus), which flex the knee and extend the hip.

Nerve and blood supply: The femoral artery and vein run through the anterior thigh, giving rise to perforating branches to the posterior compartment; the deep femoral (profunda femoris) artery supplies deep muscles. Major nerves include the femoral nerve (anterior), obturator nerve (medial), and sciatic nerve (posterior). Sensory innervation to the thigh is provided by multiple cutaneous nerves, including lateral thigh sensation via the lateral femoral cutaneous nerve.

Clinical notes: Common injuries include quadriceps or hamstring strains, contusions, and femoral fractures. Thigh compartment syndrome is a rare but serious condition requiring prompt recognition. Diseases of surrounding structures, vascular or lymphatic disorders, and groin injuries related to adductor tendons can affect thigh function.