The pronator teres is a muscle

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 of the human body

Human body

The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...

 (located mainly in the forearm

Forearm

-See also:*Forearm flexors*Forearm muscles...

) that, along with the pronator quadratus muscle

Pronator quadratus

Pronator quadratus is a square shaped muscle on the distal forearm that acts to pronate the hand.As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve...

, serves to pronate the forearm (turning it so that the palm faces posteriorly).

Structure

The pronator teres has two heads--humeral and ulnar.

The humeral head, the larger and more superficial, arises from the medial supracondylar ridge

Medial supracondylar ridge

The inferior third of the medial border of the humerus is raised into a slight ridge, the medial supracondylar ridge , which becomes very prominent below; it presents an anterior lip for the origins of the Brachialis and Pronator teres, a posterior lip for the medial head of the Triceps brachii,...

 immediately superior to the medial epicondyle

Medial epicondyle

Medial epicondyle can refer to:* Medial epicondyle of the humerus * Medial epicondyle of the femur...

 of the humerus

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

, and from the common flexor tendon

Common flexor tendon

The common flexor tendon is a tendon shared by a number of superficial flexor muscles in the forearm. It attaches to the medial epicondyle of the humerus....

 (which arises from the medial epicondyle).

The ulnar head is a thin fasciculus, which arises from the medial side of the coronoid process of the ulna

Ulna

The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...

, and joins the preceding at an acute angle.

The median nerve

Median nerve

The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus....

 enters the forearm between the two heads of the muscle, and is separated from the ulnar artery

Ulnar artery

The ulnar artery is the main blood vessel, with oxygenated blood, of the medial aspect of the forearm. It arises from the brachial artery and terminates in the superficial palmar arch, which joins with the superficial branch of the radial artery...

 by the ulnar head.

The muscle passes obliquely across the forearm, and ends in a flat tendon, which is inserted into a rough impression at the middle of the lateral surface of the body of the radius

Radius

In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...

, just below the insertion of the supinator.

The lateral border of the muscle forms the medial boundary of the triangular hollow known as the cubital fossa

Cubital fossa

The cubital fossa is the triangular area on the anterior view of the elbow of a human or other hominid animal. It is colloquially known as the "elbow pit".-Boundaries:...

, which is situated anterior to the elbow

Elbow

The human elbow is the region surrounding the elbow-joint—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm....

.

Action

Pronator teres pronates the forearm, turning the hand posteriorly. If the elbow is flexed to a right angle, then pronator teres will turn the hand so that the palm faces inferiorly. It is assisted in this action by pronator quadratus

Pronator quadratus

Pronator quadratus is a square shaped muscle on the distal forearm that acts to pronate the hand.As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve...

.

It also weakly flexes the elbow, or assists in flexion at the elbow when there is strong resistance.

Variations

Occasionally, the ulnar head is absent. Also, additional slips from the medial intermuscular septum

Intermuscular septum

Intermuscular septum can refer to:* medial intermuscular septum of arm* medial intermuscular septum of thigh* lateral intermuscular septum of arm* lateral intermuscular septum of thigh...

, from the biceps brachii, and from the brachialis occasionally occur.

Clinical aspects

Pronator teres syndrome

Pronator teres syndrome

Pronator teres syndrome is a compression neuropathy of the median nerve at the elbow.It is rare compared to compression at the wrist or isolated injury of the anterior interosseous branch of the median nerve .- Anatomy :The median nerve arises from the cubital fossa and passes between the two...

 is one cause of wrist

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;...

pain. It is a type of neurogenic pain.

• patients with the pronator teres syndrome have numbness in median nerve distribution with repetitive pronation/supination of the forearm, not flexion and extension of the elbow
• early fatigue of the forearm muscles is seen with repetitive stressful motion, especially pronation
• EMG may show only mildly reduced conduction velocities
• despite their anatomic proximity, patients with pronator teres syndrome do not have a higher incidence of AIN syndrome;
• other sites of compression:
  • ligament of Struthers
  • lacertus fibrosis
  • pronator teres muscle
  • proximal arch of the FDS
  • rare causes such as following tendon transfers for radial palsy
• dissimilarity to CTS:
  • positive Tinel's in forearm rather than at wrist
  • negative phalen's test
  • dysesthesia of palmar triangle
  • pain on resistance to pronation
  • pain in forearm on resistance to isolated flexion of the PIP joint of long and ring fingers

External links

• PTCentral
• http://www.wheelessonline.com/ortho/pronator_teres