Muscles Muscle Attachment of Forearm/ The forearm is the portion of the upper extremity extending from the elbow to the wrist. The skeletal framework for this region arises from two primary osseous structures: the radius laterally and the ulna medially. These long bones serve as origins and insertions for many muscle groups allowing for normal physiologic dynamic movements. They also provide the supportive structure needed for the passage of neurovascular bundles between the proximal and distal aspects of the upper extremity. The extent of clinical pathology involving the anatomic osseous structures of the forearm includes conditions ranging from nondisplaced and displaced fractures to osseous tumors and malignancy.[rx][rx][rx][rx]
Muscles Muscle Attachment of Forearm
The radius and ulna serve as insertion sites for several muscles originating more proximally in the arm[rx][rx]:
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Biceps brachii – inserts on the radial tuberosity, a bony prominence on the medial aspect of the proximal end of the radius; allows for flexion and supination of the forearm.
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Brachialis – inserts on the coronoid process of the ulna and the ulnar tuberosity; allows for flexion of the forearm.
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Triceps and anconeus – insert on the olecranon process of the ulna allowing for the extension of the forearm.
Within the forearm, muscles are classically grouped into anterior and posterior compartments[rx][rx]:
Anterior Compartment
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Flexor carpi radialis, palmaris longus, and the humeral heads of the pronator teres and flexor carpi ulnaris – originate from the common flexor origin. The ulnar head of the pronator teres originates from the coronoid process. The ulnar head of the flexor carpi ulnaris arises from the olecranon. The pronator teres inserts to the lateral surface of the radius and is responsible for pronation and flexion of the forearm. Each of the other muscles inserts in the wrist or hand and is responsible for more distal movements.
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Flexor digitorum superficialis – arises from the anterior border of the radius, the medial epicondyle of the humerus, and the coronoid process and inserts on the middle phalanges of the medial four digits.
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Flexor digitorum profundus – arises from the ulna and interosseous membrane and inserts on the distal phalanges.
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Flexor pollicis longus – originates from the radius and the interosseous membrane and inserts on the distal phalanx of the thumb.
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Pronator quadratus – originates from the distal end of the ulna and inserts on the distal end of the radius. Responsible for forearm pronation.
Posterior Compartment
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Brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris – originate from the distal lateral edge of the humerus. The brachioradialis inserts just proximal to the styloid process of the radius and is responsible for flexion of the forearm, especially in pronation. The remainder of the muscles originating from this area insert distally and are responsible for movements within the wrist and hand.
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Supinator – originates from the lateral epicondyle, radial collateral and annular ligaments, supinator fossa and the crest of the ulna with insertion on the lateral side of the radius. It is responsible for forearm supination.
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Abductor pollicis longus and extensor pollicis longus – originates from the posterior surface of the ulna and interosseous membrane with attachments in the hand.
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Extensor indicis – originates from the posterior surface of the distal third of the ulna and the interosseous membrane with attachment in the hand.
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Extensor pollicis brevis – originates from the posterior surface of the distal third of the radius and the interosseous membrane with attachment in the hand.