Extremity

Extremity refers to the farthest or outermost part of something. In general use, it denotes the end of a line, an edge, or boundary. In anatomy, the term is used most often to identify the limbs—the upper extremity (arm, forearm, hand) and the lower extremity (thigh, leg, foot).

The upper extremity includes bones such as the humerus, radius, ulna; the hand and wrist bones; joints such as the shoulder and elbow; and associated muscles, nerves, and vessels. The lower extremity includes the pelvis, femur, tibia, fibula, and the bones of the foot, with joints at the hip, knee, and ankle. Functionally, the extremities enable locomotion, manipulation of objects, and maintenance of balance, with motor and sensory pathways supplied by nerves of the brachial and lumbosacral plexuses.

Clinical relevance: extremities are commonly affected by injuries and conditions such as fractures, sprains, vascular insufficiency, neuropathy, and edema. Diagnostic and therapeutic considerations include imaging, physical examination, and rehabilitation.

In mathematics and related fields, extremity can mean an endpoint of a segment or curve, or the outermost limit of a set; extrema refer to maximal or minimal values.

Etymology: from Latin extremitas, outermost position.