Radius

A long bone located in the forearm, playing a critical role in arm movement and stability.

The radius is one of the two long bones in the forearm, the other being the ulna. It is situated on the lateral side of the forearm when in the anatomical position, which is the standard reference posture with the body standing upright and palms facing forward. The radius extends from the elbow joint to the wrist and varies in width along its shaft, being broader near the wrist.

Terminologia Anatomica

radius

System

Skeletal system

Function

The primary function of the radius is to facilitate movement and stability of the forearm and hand. It plays a pivotal role in various arm movements, including pronation (rotation of the forearm so the palm faces downward) and supination (rotation so the palm faces upward). The radius also serves as an attachment point for muscles that control wrist and finger movements. Additionally, it works in conjunction with the ulna to create a hinge-like motion at the elbow and to provide a stable base for the wrist joint. The interaction between the radius and ulna during rotation enables intricate wrist movements necessary for many daily activities such as writing, gripping, and lifting.

Location

Positioned laterally to the ulna, the radius is located between the elbow and wrist. Its proximal end is near the elbow joint, where it articulates with the humerus and partially with the ulna. The distal end of the radius is located at the wrist joint, where it forms a critical connection with the carpal bones. The unique positioning of the radius allows it to rotate around the ulna, contributing to the rich range of motion in the forearm and wrist. The distinct shape and contours of the radius are adapted to its roles in both stability and mobility.

Did You Know?

The radius is approximately 24 centimeters long on average, but its length can vary between individuals.
In people, the radius can fracture due to a fall onto an outstretched hand, resulting in a common injury known as a 'Colles' fracture.'
The name 'radius' comes from the Latin word for 'ray,' alluding to its elongated shape radiating from the elbow.
The radius can be divided into three sections: the proximal end, the shaft, and the distal end, each with specific anatomical features.
During forearm rotation, the radius rotates around the stationary ulna like a wheel around an axle.