The distal radioulnar articulation (also known as the distal radioulnar joint, or inferior radioulnar joint) is a synovial pivot joint between the two bones in the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in anat ...

; the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

and

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

. It is one of two joints between the radius and ulna, the other being the

proximal radioulnar articulation The proximal radioulnar articulation, also known as the proximal radioulnar joint (PRUJ), is a synovial pivot joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament. ...

. The joint features an articular disc, and is reinforced by the

palmar Palmar may refer to: Anatomy, relating to the palm of the hand * Palmar aponeurosis, deep fascia connecting and within the muscles of the palm * Palmar arches (disambiguation), various combinations of arteries in the hand and arm * Palmar art ...

and dorsal radioulnar

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

Structure

The distal radioulnar articulation is formed by the

head of ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of the ...

, and the

ulnar notch The articular surface for the ulna is called the ulnar notch (sigmoid cavity) of the radius; it is in the distal radius The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the latera ...

of the distal

Articular disc

The joint features a triangular articular disc that is attached to the inferior margin of the ulnar notch by its base, and to a fossa at the base of the

styloid process of the ulna The styloid process of the ulna is a bony prominence found at distal end of the ulna in the forearm. Structure The styloid process of the ulna projects from the medial and back part of the ulna. It descends a little lower than the head. The head ...

by its apex. The articular disc acts to firmly bind the distal extremities of the two bones together.

Ligaments

The articulation is reinforced by the

palmar radioulnar ligament The palmar radioulnar ligament (volar radioulnar ligament, anterior radioulnar ligament) is a narrow band of fibers extending from the anterior margin of the ulnar notch of the radius to the front of the head of the ulna The ulna (''pl''. ulnae ...

, and dorsal radioulnar ligament.

Function

The function of the radioulnar joint is to lift and maneuver weight load from the distal radioulnar joint to be distributed across the forearm’s

and

as a load-bearing joint.

Supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

of the radioulnar joint can move from 0 degrees neutral to approximately 80-90 degrees where

pronation Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative ...

of the radioulnar joint can move from 0 degrees neutral to approximately 70-90 degrees. Supination (palms facing up) vs. pronation (palms facing down). Muscles that contribute to function are all supinator (

biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join t ...

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way o ...

, and

supinator In human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm. Structure Supinator consists of two planes of fibers, between whi ...

) and pronator muscles (

pronator quadratus Pronator quadratus is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand. Structure Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the ...

, and pronator peres).

Clinical significance

Injuries to the distal radioulnar articulation often result from falls onto an outstretched hand. Injury can occur with concurrent fracture of the distal radius, the ulna, or can be isolated. For the upper limit of the distal radioulnar distance, sources vary between 2 mm and 5 mm. A classification system has been proposed by

Estaminet French cuisine () is the cooking traditions and practices from France. It has been influenced over the centuries by the many surrounding cultures of Spain, Italy, Switzerland, Germany and Belgium, in addition to the food traditions of the r ...

and colleagues.Estaminet et al. Estaminet-Klassifikation von distal radioulnar Aussprache-Trauma. 20. Jahresversammlung der europäischen Orthopädischen Forschungsgesellschaft (EORS 2012), am 26–28 September, Amsterdam, Die Niederlande

Estaminet Classification

Estaminet classified injuries of the distal radioulnar articulation into four categories with two subclasses: purely ligamentous (subclass A) and those with associated boney injury (subclass B). * Estaminet I - Attenuation on MRI only *

Estaminet II French cuisine () is the cooking traditions and practices from France. It has been influenced over the centuries by the many surrounding cultures of Spain, Italy, Switzerland, Germany and Belgium, in addition to the food traditions of the re ...

- Volar distal radioulnar ligament is involved. Unstable in supination. Fixation should be in pronation. *

Estaminet III French cuisine () is the cooking traditions and practices from France. It has been influenced over the centuries by the many surrounding cultures of Spain, Italy, Switzerland, Germany and Belgium, in addition to the food traditions of the re ...

- Dorsal distal radioulnar ligament is involved. Unstable in pronation. Fixation should be in supination. *

Estaminet IV French cuisine () is the cooking traditions and practices from France. It has been influenced over the centuries by the many surrounding cultures of Spain, Italy, Switzerland, Germany and Belgium, in addition to the food traditions of the re ...

- Both ligaments are involved. Unstable in both supination and pronation. Fixation is in neutral.

Additional images

Image:RightHumanPosteriorDistalRadiusUlnaCarpals.jpg, Distal ends of radius and ulna along with the bones of the wrist and hand Image:Gray421.png, Transverse section across distal ends of radius and ulna.

References

External links

Dartmouth Anatomy
{{Authority control Upper limb anatomy Joints