• Clinical science

Arm and elbow

The humerus

The humerus is the bone of the arm that articulates with the scapula to form the shoulder joint and with the radius and ulna to form the elbow joint.


The muscles of the arm can be categorized into two groups: flexors and extensors. They are covered by the brachial fascia and divided into anterior (flexor) and posterior (extensor) compartments by the medial intermuscular septum and the lateral intermuscular septum.

Anterior compartment (flexors)

The anterior compartment contains 3 muscles that are flexors of the arm or forearm and are innervated by the musculocutaneous nerve

Muscle Origin Insertion Innervation Function
Biceps brachii
  • Shoulder: internal rotation
    • Long head: shoulder abduction
    • Short head: shoulder adduction
  • Elbow: flexion
  • Forearm: supination
    • The strongest supinator


Lies deep to the biceps brachii

  • Tuberosity of the ulna


Lies deep to the biceps brachii

Elbow flexors are innervated by the musculocutaneous nerve!

Biceps tendon tear: Tear of the long head of the biceps brachii results in superior migration of the humeral head. This occurs because the humeral head of the long biceps tendon no longer presses against the glenohumeral joint surface and are overcome by the effect of the torso wall muscles.

Posterior compartment (extensors)

Contains 2 muscles that are elbow extensors and are innervated by the radial nerve

Muscle Origin Insertion Innervation Function
Triceps brachii
  • Radial nerve
Anconeus muscle
  • Dorsal ulnar surface distal of the olecranon

The elbow extensors are innervated by the radial nerve!

The bicipital grooves

There are 2 bicipital grooves that serve as channels for important neurovascular pathways

Medial bicipital groove Lateral bicipital groove



  • Radial nerve


Motor innervation

Sensory innervation

Dermatomal distribution of the arm

  • Skin over shoulder: C4
  • Outer arm: C5
  • Lower posterior arm (elbow): C6
  • Lower inner arm: T1
  • Upper inner arm: T2

Elbow joint

Cubital fossa (antecubital fossa)

A triangular space on the anterior aspect of the elbow joint

To remember the contents of the cubital fossa, remember “RobiN BeaTs BAt MaN”: Radial Nerve, Biceps Tendon, Brachial Artery, Median Nerve

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last updated 06/20/2019
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