Joints of the upper limb

Overview

Upper-limb joints balance mobility with stability. The shoulder provides a wide range of movement, while the elbow positions the forearm and the hand joints shape grip.

Ligaments, joint geometry and surrounding muscles contribute in different proportions at each level.

The sternoclavicular joint is the only direct bony articulation connecting the upper limb to the axial skeleton. Scapular movement then works with the glenohumeral joint to position the arm.

Joint types and surfaces

Circumduction combines movements around two axes. It is not the same as axial rotation, although thumb opposition includes a rotational component.

Sternoclavicular and acromioclavicular joints

An articular disc divides the sternoclavicular cavity. Anterior and posterior sternoclavicular ligaments reinforce its capsule; the interclavicular ligament links the clavicles above the manubrium.

The costoclavicular ligament anchors the medial clavicle to the first rib and limits excessive movement.

At the acromioclavicular joint, the capsular acromioclavicular ligament supports the articulation. The coracoclavicular ligament is the major suspensory connection between clavicle and scapula.

Its conoid part is posteromedial and its trapezoid part anterolateral.

Scapular rotation requires movement at both clavicular joints. A shoulder cannot reach its full overhead position through glenohumeral motion alone.

Glenohumeral capsule and stability

The glenoid is shallow and is deepened by the fibrocartilaginous labrum. The humeral head is much larger than its socket, allowing movement but limiting bony restraint.

The capsule attaches around the glenoid margin and near the anatomical neck of the humerus. It is lax inferiorly to allow abduction.

The glenohumeral ligaments thicken its anterior aspect; the coracohumeral ligament supports the superior capsule.

Supraspinatus, infraspinatus, teres minor and subscapularis blend with the capsule. Their tendons provide dynamic stability, but the inferior capsule lacks comparable cuff reinforcement.

The coracoacromial arch forms a protective roof above the joint.

The transverse humeral ligament bridges the tubercles over the biceps tendon.

The long head of biceps attaches to the supraglenoid region and superior labrum. Its tendon is intracapsular but outside the synovial cavity, then passes into the intertubercular sulcus.

The subacromial bursa lies between the cuff and the overlying arch/deltoid; it does not normally communicate with the joint cavity.

Shoulder movements and supply

Classically, the first approximately 15 degrees of abduction are associated with supraspinatus, the next phase mainly with deltoid, and elevation above shoulder level with scapular rotation. In real movement their actions overlap.

The familiar approximately 2:1 glenohumeral-to-scapular contribution is an overall teaching guide, not a constant ratio throughout elevation.

The joint receives articular branches including the suprascapular and axillary nerves. Circumflex humeral and suprascapular vessels contribute to its blood supply.

Elbow and radioulnar joints

The trochlear notch grips the humeral trochlea, providing substantial bony stability. The ulnar collateral ligament resists valgus stress medially.

The lateral ligament complex supports the lateral elbow, while the annular ligament holds the radial head against the radial notch without preventing rotation.

Biceps and brachialis flex the elbow; triceps extends it. The carrying angle is the lateral deviation of the forearm when the elbow is extended and the forearm supinated.

Avoid confusing this normal alignment with fracture deformity.

During pronation the radius crosses anterior to the ulna. The radial head spins proximally while the distal radius moves around the ulnar head. Supination reverses the movement.

Pronator teres and quadratus pronate; biceps and supinator supinate.

The interosseous membrane joins the shafts, provides muscle attachment and transfers load between radius and ulna. Distally, an articular disc separates the ulnar head from the carpus and contributes to distal radioulnar stability.

The elbow receives branches from musculocutaneous, radial, median and ulnar nerves, with blood from the surrounding collateral and recurrent arterial network.

The wrist receives anterior interosseous and deep radial/ulnar articular branches. Periarticular radial and ulnar vessels supply the wrist and hand joints.

Wrist and hand

The radiocarpal joint includes the distal radius and articular disc proximally, with scaphoid, lunate and triquetrum distally. The ulna has no direct articulation with the carpal bones.

The pisiform articulates separately with the triquetrum.

Palmar and dorsal radiocarpal ligaments, together with collateral ligaments, support the wrist. The midcarpal articulation also contributes substantially to wrist movement.

Flexor carpi radialis and ulnaris flex the wrist; the radial wrist extensors and extensor carpi ulnaris extend it. Radial deviation combines radial flexor and extensor action; ulnar deviation combines the ulnar pair.

The thumb saddle joint permits flexion, extension, abduction, adduction and opposition. Opposition brings the thumb pulp towards another fingertip through a combination of movements at the first carpometacarpal joint.

Finger metacarpophalangeal collateral ligaments become tight in flexion. Palmar plates resist hyperextension.

The lumbricals and interossei flex these joints while extending the interphalangeal joints through the extensor expansions. Interphalangeal collateral ligaments guide hinge movement and resist sideways displacement.

Clinical relevance

Anterior shoulder dislocation

How it happens: Forced abduction and lateral rotation can drive the humeral head anteroinferiorly, damaging capsule or labrum and stretching the axillary nerve.

What you see: The shoulder loses its rounded contour, with possible deltoid weakness and altered lower-deltoid sensation.

Acromioclavicular separation

How it happens: A shoulder impact disrupts acromioclavicular restraints and, in severe injury, the coracoclavicular ligament.

What you see: The scapula and attached arm descend relative to the clavicle, producing a prominent lateral clavicle and painful movement.

Pulled elbow

How it happens: Traction on a young child’s pronated forearm displaces part of the annular ligament around the radial head.

What you see: The child avoids using the arm despite little obvious deformity. The immature radial head and ligament explain the age distribution.

Frozen shoulder

How it happens: The shoulder capsule thickens and contracts.

What you see: Both active and passive movement become restricted, particularly external rotation. This differs from isolated tendon weakness with better preserved passive movement.

Quick revision

• Sternoclavicular joint is the only bony link to the axial skeleton.
• Coracoclavicular ligament has conoid and trapezoid parts.
• Rotator cuff supports the shoulder capsule except inferiorly.
• Long-head biceps tendon is intracapsular but extrasynovial.
• Radius rotates around the ulna during pronation and supination.
• Ulna does not directly articulate with carpal bones; thumb opposition depends on the first carpometacarpal saddle joint.

Sources: Snell's Clinical Anatomy by Regions, supplied Upper Limb chapter; UHS PGET Paper I MBBS Table of Specifications. Supplementary clinical testing and developmental context follow standard examination conventions and Duke Embryology where relevant. Picture links are visual study resources. Text and tables written independently for The House Job.

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