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The radius is one of the 2 bones that comprise the forearm, the other being the ulna. It forms the radio-carpel joint at the wrist and also the radio-ulnar joint at the elbow. It is in the lateral forearm once in the anatomical place. It is the smaller of the two bones.

You are watching: In the anatomical position, the lateral forearm bone is the radius.

Structure

Proximal radius

The proximal radius consists of the radial head, neck and tuberosity.

The radial head is cylindrical which articulates via the capitellum of the humerus<1>. The head rotates within the annular ligament to develop supicountry and also pronation of the forearm.<2>

The neck and tuberostiy support the head and provide points of attachments for supinator brevis and Biceps brachi<1>

Radial shaft

The shaft of the radius is slightly curved into convex from the body. The majority of the shaft has actually three borders: anterior, posterior and also interosseous.

Distal radius<2>

The distal radius has five surfaces:

Lateral - which exoften tends to develop the styloid processMedial - is composed of a concave ulnar notch to articulate with the ulnar head in pronationPosterior - convex and also consists of a significant ridge referred to as Lister"s tubercleAnterior - smooth and also forms a distinct margin

Function

The radius" primary attributes are to articulate via the ulna and humerus at the elbow to provide supination and also pronation. Then to articulate via the lunate and scaphoid to provide all the motions of the wrist.

Articulations

Elbow

The radius articulates with the ulna in a synovial pivot joint. The radial head rotates within the annular ligament and radial notch on the ulna to develop procountry of the forearm.<3>

The radius and ulna likewise articulate distally in reverse to their articulation at the elbow to create supicountry. This activity occurs with the head of the ulna being received into the ulnar notch of the radius. <3>


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Wrist

The radius articulates via the initially row of carpel bones: mostly scaphoid laterally and also the lunate medially to develop the radio-carpel joint, triquetral only provides intermittent contact on ulnar abduction. The radio-carpel joint is an ellipsoid joint by which the scaphoid, lunate and also triquetral bones develop a convex surconfront to articulate with the distal radius" concavity.

The radio-carpel joint has 4 movements: flexion, expansion, radial and ulnar deviation.

Muscle attachments

Proximal

Biceps brachii attaches to the radial tuberosity.

Supinator, flexor pollicis longus and the flexor digitorum superficialis affix to the top third component of the shaft of the radius.

Mid shaft

Extensor Pollicis Brevis muscle, abductor pollicis longus muscle, and also pronator teres all connect to the mid shaft of the radius

Distal

Pronator quadratus muscle and also the tendon of the supinator longus affix to the distal quarter of the radial shaft.

Clinical relevance

Colles fracture: is a fracture of the distal radius. Commjust led to by a fall on outextended hand also (FOOSH)

Radial head fracture: typically brought about from FOOSH this deserve to be accompanied by disarea of the radius and/or ulna which have the right to complicate the monitoring of this injury.

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Osteoarthritis of the wrist or elbow

Radial dysplasia or radial club hand have the right to take place in paediatric patients as a congenital problem through which tbelow is a shortening of the radius or also finish absence of radius in the forearm. This deserve to result in thumb abnormalities and the need for surgical treatment to boost function.<6>