- Clinical science
The upper arm, or brachium, extends between the shoulder joint and elbow. The shoulder joint connects the upper arm to the torso and the shoulder girdle, while the elbow joint connects it to the forearm. The muscles of the upper arm move the elbow joint (flexion and extension) and the forearm (pronation and supination), as well as stabilize and move the shoulder joint (internal rotation and flexion). This learning card covers the bones, muscles, vasculature, lymphatics, and innervation of the upper arm and elbow.
Theare discussed elsewhere, as are the .
- Anatomical neck of the humerus: constriction that separates the head of the humerus from the tubercles and allows attachment of the ligaments of the glenohumeral joint
Surgical neck of the humerus
- Constriction below the tubercles
- The axillary nerve and pass around the dorsal part of the surgical neck of the humerus together.
- Greater tubercle of the humerus: site of insertion of the supraspinatus, infraspinatus, and teres minor of the rotator cuff
- Lesser tubercle of the humerus: site of insertion of the subscapularis of the rotator cuff
- Bicipital groove (intertubercular sulcus); : deep groove between the tubercles in which the tendon of the long head of biceps brachii lies; also the site of insertion for pectoralis major, teres major, and latissimus dorsi
- Deltoid tuberosity: rough area on the superolateral aspect of the shaft of the humerus into which the deltoid is inserted
- Radial groove: : groove on the mid-posterolateral surface of the shaft in which the radial nerve and deep brachial artery run together
Distal humerus (medial to lateral)
Medial epicondyle: medial-most bony prominence of the humerus
- Site of origin of most forearm flexors and pronator teres
- Ulnar groove
- Trochlea; : dumbbell-shaped bony projection that articulates with the ulna
- Coronoid fossa; : depression above the trochlea on the ventral humerus that receives the coronoid process of ulna when the forearm is flexed
- Capitulum; : spherical bony prominence that articulates with the head of the radius
- Radial fossa; : depression above the capitulum on the ventral humerus that receives the head of the radius when the forearm is flexed
Lateral epicondyle: lateral-most bony prominence
- Site of origin of most forearm extensors and supinator
- Olecranon fossa; : bony depression on the dorsal aspect of the distal humerus; receives the olecranon process of the ulna when the forearm is extended
- Medial epicondyle: medial-most bony prominence of the humerus
Humerus fractures can also involve injuries to neighboring structures. From proximal to distal, the nerves that can be injured along with a humerus fracture are the nerves of the A-R-M (axillary, radial, median). Fractures at the surgical neck of the humerus can injure the axillary nerve (along with the posterior circumflex humeral artery). Fractures of the humeral shaft can injure the radial nerve (along with the deep brachial artery). Fractures of the distal humerus (supracondylar fractures) can injure the median nerve (along with the brachial artery).
The muscles of the arm can be categorized into two groups: flexors and extensors. They lie deep to the brachial fascia and are divided into anterior (flexor) and posterior (extensor) compartments by the medial intermuscular septum and the lateral intermuscular septum.
For specific tests to assess the function of these muscles, see “Motor function” in neurological examination.
Anterior compartment of the arm (flexors)
The anterior compartment contains three muscles that are elbow flexors, all of which are innervated by the musculocutaneous nerve.
|Biceps brachii|| || |
| || |
| || |
The elbow flexors are innervated by the musculocutaneous nerve.
A common tendon rupture of the arm is Popeye sign” on examination. , which classically causes the “
Posterior compartment of the arm (extensors)
The posterior compartment contains two muscles that are elbow extensors, both of which are innervated by the radial nerve.
|Triceps brachii|| || |
|Anconeus muscle|| || |
The elbow extensors are innervated by the radial nerve.
Surface anatomy of the arm
There are two bicipital grooves between the muscle groups of the arm that serve as channels for important neurovascular pathways. They are different from the humerus.that lies between the tubercles of the
|Medial bicipital groove||Lateral bicipital groove|
| || |
- Origin: : inferolateral border of the teres major; continuation of the
- Deep brachial artery; (profunda brachii): supplies the triceps muscle
- Small branches to the elbow anastomosis (the superior and inferior ulnar collateral arteries)
- Terminal branches (See also “Vasculature and lymphatics” in for more details.)
- : supplies the forearm and hand
- : supplies the forearm and hand
Superficial veins (See also “Veins” in for more details.)
- Deep veins: brachial veins
- The lymphatics follow the superficial and deep veins.
- The lateral aspect of the upper limb is drained by lymphatics that follow the cephalic vein and ultimately drain into the lateral and infraclavicular lymph nodes.
- The medial aspect of the upper limb is drained by lymphatics that accompany the basilic vein and ultimately drain into the lateral .
Motor and sensory innervation of the arm and elbow
| || |
| || |
| || |
| || |
- For more on the clinical presentation of upper limb nerve lesions, see the section “Nerve injuries in the upper body” in peripheral nerve injuries.
- For tests to assess the function of these nerves, see “Motor function” and “Sensation” in neurological examination.
Dermatomal distribution of the arm
- Skin over shoulder: C4
- Lateral arm: C5
- Posterior arm (elbow): C6
- Inferomedial arm: T1
- Superomedial arm: T2
- Type of joint: complex synovial hinge joint between the distal end of the humerus and the proximal ends of the radius (humeroradial joint) and ulna (humeroulnar joint), as well as between the radius and ulna (radioulnar joint); connects the arm and forearm
Composition: consists of three articulations
- Humeroulnar joint: articulation between the trochlear notch of the ulna and the trochlea of the humerus that allows elbow flexion/extension
- Humeroradial joint: articulation between the head of radius and the capitulum of the humerus that allows forearm pronation/supination
- Radioulnar joint: articulation between the head of the radius and proximal ulna that allows forearm pronation/supination
- Radial collateral ligament (lateral ligament): from the lateral epicondyle of the humerus to the radial notch of the ulna and the annular ligament of the radius (proximal radioulnar joint)
- Ulnar collateral ligament (internal ligament): from the medial epicondyle of the humerus to the coronoid process and olecranon of the ulna
- Annular ligament of the radius (ring-shaped ligament): surrounds the head of the radius and anchors the radial head to the radial notch of the ulna
- Blood supply: elbow anastomosis
- The three bony prominences of the elbow joint are the medial and lateral epicondyles and the olecranon process.
- These three points align in a horizontal line when the elbow is extended.
- They align in a triangular shape, with the apex being the olecranon process, when the elbow is flexed to 90°.
- three-point relationship on examination : may cause disruption of the
- three-point relationship is maintained :
Radial head subluxation (nursemaid elbow) is a partial subluxation of the radial head at the radiohumeral joint and is caused by excessive axial traction. It is the most common elbow injury in children < 5 years old.
- Definition: : triangular space on the anterior aspect of the elbow joint
- Floor: brachialis and supinator muscles
For the contents of the cubital fossa (from lateral to medial), remember “Really Need Beer To Be At My Nicest” = Radial Nerve, Biceps Tendon, Brachial Artery, Median Nerve.References: