Quadrate ligament

At a glance

English

Quadrate ligament

Latin (TA2)

Ligamentum quadratum

System

Ligament

Region

Upper limb

Side

Paired, left and right

About the quadrate ligament

Beneath the annular ligament at the proximal radio-ulnar joint is a short, thin band, the quadrate ligament, also called the ligament of Denucé after the French anatomist who described it in 1854. It closes the lower part of the joint, the space between the bottom of the annular ligament and the neck of the radius, and so covers the lower part of the elbow joint capsule.

The ligament is a flat, roughly square sheet. One edge is fixed along the lower border of the radial notch of the ulna and the other along the medial side of the radial neck. Its front and back borders are reinforced by fibres from the lower edge of the annular ligament. In adults it measures about a centimetre in length, a little less in width, and only around a millimetre in thickness. Beneath it a fold of synovial membrane, the sacciform recess, bulges down around the radial neck.

By tying the radial neck to the ulna, the ligament helps hold the radial head against the radial notch. It also checks forearm rotation: it tightens towards the end of supination, limiting that movement by roughly 10 to 20 degrees, and to a smaller degree checks pronation, by about 5 to 8 degrees. It thus adds to the stability of the proximal radio-ulnar joint and to the strength of the lower part of the elbow capsule.

Whether it is a true ligament has long been argued. Denucé himself suggested it might be no more than a prolonged synovial pouch, or part of the annular ligament, and some later anatomists found only a thin fibrous layer of capsule. Others described a stronger front border, while more recent dissection studies reported a uniform thickness and a real mechanical role. The Paris Nomina Anatomica of 1955 recognised it as a structure in its own right. Its role in pulled elbow and in radial head fractures is still a subject of study.

Attachments and function

Attaches from

The lower border of the radial notch of the ulna.

Attaches to

The medial aspect of the neck of the radius.

Function

Reinforces the lower capsule of the elbow and proximal radio-ulnar joint, secures the radial neck against the ulna and limits extreme supination and, slightly, pronation.

Nerve supply

Articular branches of the median and radial nerves around the elbow.

Blood supply

Branches of the interosseous recurrent and ulnar recurrent arteries.