Definition

By: Gregory R. Waryasz, MD

The pronator teres muscle of the musculoskeletal system is characterized by being having a humeral and an ulnar head.

It is part of the forearm.  It consists of skeletal muscle fibers.

Its unique structural features include its fusiform shape.  It is the most laterally located superficial forearm flexor muscles.  The lateral border is the medial cubital fossa.

The common proximal attachment of all the superficial flexor-pronator muscles is the common flexor tendon to the medial epicondyle of the humerus.

The origin of the ulnar head is the coronoid process.  The origin of the humeral head is the medial epicondyle of the humerus.

The insertion is the middle convexity of the lateral radius.

The blood supply is from the ulnar and radial artery and venous drainage is from the accompanying veins.

The innervation is from the median nerve.

The pronator teres muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the pronator teres is to pronate and flex the forearm at the elbow.  It works synergistically with the pronator quadrates.

Common diseases include pronator teres syndrome and medial epicondylitis.

Pronator teres syndrome is a cause of wrist pain and numbness in the median nerve distribution due to a compressive neuropathy. It is associated with repetitive pronation and supination of the forearm.  The sites of compression are the ligament of Struthers, lacterus fibrosis, pronator teres muscle, and the proximal arch of the flexor digitorum superficialis.  There is usually a positive Tinel’s sign in the forarm.

Medial epocondylitis is a condition of pain and tenderness in the medial elbow at the site of the common flexor tendon origin.  It may begin as a microtear between the pronator teres and the flexor carpi radialis.  It may be associated with ulnar neuritis.

Commonly used diagnostic procedures include clinical history, physical exam, and MRI. EMG can be helpful to diagnose pronator teres syndrome.

It is usually treated with physical therapy, a brace, and NSAIDs initially for medial epicondylitis.  A corticosteroid injection may provide some relief.  Surgery may be helpful if physical therapy fails.  Pronator teres syndrome is treated with rest, ice, physical therapy, and icing initially.  A corticosteroid injection may provide some relief. Surgical decompression may be helpful for some cases.

References

Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.

Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.

Wheeless’ Textbook of Orthopaedics:Pronator Teres (http://www.wheelessonline.com/ortho/pronator_teres)