In human anatomy, the extensor carpi ulnaris is a

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

located on the

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 ...

r side of 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 ...

. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from

anatomical position The standard anatomical position, or standard anatomical model, is the scientifically agreed upon reference position for anatomical location terms. Standard anatomical positions are used to standardise the position of appendages of animals with r ...

. Being an extensor muscle, extensor carpi ulnaris is located on the posterior side of the forearm.

Origin and insertion

It originates from the lateral epicondyle of the humerus and the posterior border of the

, and crosses the forearm to the

r (medial) side to insert at the base of the 5th metacarpal.

Action

The extensor carpi ulnaris extends the

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carp ...

, but when acting alone inclines the hand toward the ulnar side; by its continued action it extends the elbow-joint. The muscle is a minor extensor of the carpus in carnivores, but has become a flexor in

ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...

s. In this case it would be described as ''ulnaris lateralis''.

Innervation

Despite its name, the extensor carpi ulnaris is innervated by the posterior interosseous nerve (C7 and C8), the continuation of the

deep branch of the radial nerve The radial nerve divides into a superficial (sensory) and deep (motor) branch at the cubital fossa. The deep branch of the radial nerve winds to the back of the forearm around the lateral side of the radius between the two planes of fibers of the S ...

. It would therefore be paralyzed in an injury to the posterior cord of the

brachial plexus The brachial plexus is a network () of nerves formed by the anterior rami of the lower four cervical nerves and first thoracic nerve ( C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in t ...

Injuries

A common injury to the extensor carpi ulnaris is

tennis elbow Tennis elbow, also known as lateral epicondylitis or enthesopathy of the extensor carpi radialis origin, is a condition in which the outer part of the elbow becomes painful and tender. The pain may also extend into the back of the forearm. Onse ...

. This injury occurs in people who participate in activities requiring repetitive arm, elbow, and wrist, especially when they are tightly gripping an object. Some symptoms of an extensor carpi ulnaris injury include pain when shaking hands or when squeezing/gripping an object. The pain worsens when a person moves their wrist with force. This pain intensifies because the extensor carpi ulnaris has an injury near the elbow area and as a person moves their arm, the muscle contracts, thus causing it to move over the medial epicondyle of the humerus. As a result, this causes irritation to the already existing injury. Some treatments for tennis elbow include occupational therapy, physical therapy, anti-inflammatory medication, and rest from the activity that caused the injury. A similar injury involving the medial elbow is known as golfer's elbow.

Injury treatment and diagnosis

An ECU injury most often requires imaging (CT, MRI, ultrasound) for diagnosis. After the ECU injury is diagnosed, a physician will choose a course of treatment, which depends upon the severity of the injury. Conservative treatments include immobilization and stabilization of the affected wrist by placing it in a cast. A long arm cast may be required in order to ensure that all wrist movement has been stopped. The duration of the immobilization is at the treating physician's discretion. After the immobilization period has ended, the cast will be removed and further analysis of the injury will be required. If the injury did not improve with the conservative courses of treatment, or if the injury was initially too severe for conservative treatment, invasive procedures may become necessary. Steroid injections and surgical procedures are the most prominent invasive procedures. Surgical repair or reconstruction of the ECU is not often required, yet a severe ECU injury may cause these approaches to be necessary.

Additional images

References

External links

{{Authority control Muscles of the upper limb