Orthopaedic Surgery - Elbow Anatomy and Examination

Basics

The elbow is a complex trochoginglymoid joint, meaning that it functions primarily as a hinge while also permitting rotational motion of the forearm.

Functionally, the elbow consists of three articulations: the humeroulnar joint, radiocapitellar joint, and proximal radioulnar joint.

Together, these joints permit flexion and extension of the elbow as well as pronation and supination of the forearm.

Osseous Anatomy

Humeroulnar Joint

The humeroulnar joint is formed by articulation of the trochlea of the distal humerus with the greater sigmoid, or trochlear, notch of the proximal ulna.

This articulation is the major contributor to elbow flexion and extension.

Coronoid and Radial Fossae

Anteriorly, the distal humerus contains the coronoid fossa and radial fossa.

During elbow flexion, these depressions accommodate the coronoid process of the ulna and radial head, respectively.

Olecranon Fossa

Posteriorly, the olecranon fossa receives the olecranon process of the ulna during elbow extension.

This relationship permits near-complete extension while maintaining joint congruity.

Ulnar Nerve Groove

A groove lies posterior to the medial epicondyle through which the ulnar nerve passes.

Because the nerve is superficial in this region, it is vulnerable to compression, irritation, trauma, and subluxation.

Radiocapitellar Joint

The radiocapitellar articulation is formed between the radial head and capitellum of the distal humerus.

The superior surface of the radial head is concave and articulates with the convex capitellum.

Radial Head

The radial head is covered with articular cartilage over most of its circumference, approximately 280°.

This allows it to articulate smoothly not only with the capitellum but also with the lesser sigmoid notch of the ulna.

Function of the Radiocapitellar Joint

The radiocapitellar joint contributes to elbow stability and allows rotation of the radius during forearm pronation and supination.

Proximal Radioulnar Joint

The proximal radioulnar joint is formed by the articulation of the radial head with the lesser sigmoid, or radial, notch of the ulna.

The radial head rotates within this articulation, producing a pivot mechanism essential for pronation and supination.

Ligaments

Ulnar Collateral Ligament

The ulnar collateral ligament (UCL) is the major medial stabilizer of the elbow.

It resists valgus stress and is especially important during overhead throwing.

The anterior bundle is the primary restraint to valgus loading through much of the functional arc.

Lateral Collateral Ligament Complex

The radial or lateral collateral ligament complex stabilizes the lateral elbow.

Its components resist varus stress and posterolateral rotatory instability.

Muscles

Biceps Brachii

The biceps brachii functions as an elbow flexor and powerful forearm supinator.

Its contribution to supination is particularly important when the elbow is flexed.

Brachialis

The brachialis is a strong elbow flexor.

Because it inserts on the ulna, its flexion function is relatively independent of forearm position.

Triceps Brachii

The triceps brachii is the primary extensor of the elbow.

Its tendon inserts on the olecranon.

Pronator Teres

The pronator teres contributes to forearm pronation and also assists with elbow flexion.

Nerves

Median Nerve

The median nerve crosses the elbow anteriorly.

It lies superficial to the brachialis muscle and generally medial to the brachial artery.

Distally, it supplies most of the flexor muscles of the forearm as well as important motor and sensory structures in the hand.

Ulnar Nerve

The ulnar nerve passes superficially behind the medial epicondyle through the cubital tunnel.

This location is a common site for ulnar nerve compression and subluxation.

The nerve ultimately supplies most of the intrinsic muscles of the hand.

Radial Nerve

The radial nerve crosses the elbow anterior to the lateral epicondylar region.

Near the elbow, it divides into the superficial radial sensory nerve and the posterior interosseous nerve.

Its motor branches supply the elbow, wrist, and finger extensor musculature.

History

A complete history should be obtained before examination.

Important information includes the patient’s activities, occupation, sport participation, hand dominance, comorbidities, previous injuries, and prior elbow surgery.

Symptoms should be characterized according to location, duration, aggravating activities, instability, neurologic symptoms, and mechanical complaints such as locking or catching.

Physical Examination

Inspection

Both upper extremities should be exposed from the shoulder girdle to the hand.

The examiner should compare the two sides from both the anterior and posterior perspectives.

The neck, shoulder, wrist, and hand should also be evaluated because pathology in these regions may refer symptoms to the elbow.

Carrying Angle

The physiologic carrying angle is a mild valgus alignment of the forearm relative to the humerus.

Typical values are approximately 11–14° of valgus in males and 13–16° in females.

Marked asymmetry may suggest previous trauma, growth disturbance, or deformity.

Visual Assessment

The examiner should look for muscular hypertrophy or atrophy, swelling, cutaneous lesions, ecchymosis, deformity, signs of acute trauma, and scars from previous surgery.

Palpation

Digital palpation should be systematic and directed toward identifying the specific anatomic structure responsible for pain.

Important areas include the medial and lateral epicondyles, radial head, olecranon, distal biceps tendon, UCL, lateral ligament complex, cubital tunnel, and joint lines.

Range of Motion

Active and passive elbow motion should be compared bilaterally.

Normal motion is approximately 0–140° of flexion, with some individuals demonstrating up to about 10° of hyperextension.

Forearm rotation is approximately 80° of supination and 80° of pronation.

Functional Range of Motion

Most activities of daily living can be performed with approximately 30–130° of elbow flexion, together with about 50° of pronation and 50° of supination.

Loss of motion outside this functional arc may therefore be tolerated better than loss within it.

Strength Testing

Isometric strength should be assessed and compared with the contralateral side.

Elbow flexion, extension, pronation, and supination should be tested individually.

Pain during resisted testing may help localize tendon pathology.

Elbow Effusion

An elbow effusion can be palpated most readily over the lateral joint in the center of the triangle formed by the lateral epicondyle, radial head, and olecranon tip.

An effusion suggests intra-articular pathology and may be accompanied by loss of terminal extension.

Lateral Epicondylitis

Lateral epicondylitis, commonly called tennis elbow, usually results from repetitive overuse of the wrist and finger extensor mechanism.

The extensor carpi radialis brevis is particularly commonly involved.

Tenderness

Maximal tenderness is typically located just anterior and distal to the lateral epicondyle, near the origin of the extensor carpi radialis brevis.

Resisted Wrist Extension Test

With the forearm pronated, the patient attempts to extend the wrist against resistance.

Reproduction of pain over the lateral epicondyle constitutes a positive test.

Chair Test

The chair test may also provoke symptoms.

The patient attempts to lift a chair with the forearm pronated and elbow extended, reproducing pain at the lateral epicondyle.

Medial Epicondylitis

Medial epicondylitis, or golfer’s elbow, affects the common flexor-pronator origin.

Pain is localized over the medial epicondyle and may be exacerbated by resisted wrist flexion or forearm pronation.

Resisted Flexion and Pronation Test

The elbow is placed in slight flexion with the forearm initially supinated.

The patient performs resisted wrist flexion and/or pronation.

Reproduction of pain at the medial epicondyle supports the diagnosis.

Olecranon Bursitis

The olecranon bursa lies subcutaneously over the posterior olecranon.

Inflammation may result from repetitive trauma, direct injury, hemorrhage, infection, or rheumatologic disease.

Examination Findings

The patient may have localized swelling over the olecranon, with or without erythema.

Tenderness varies according to the cause.

Septic bursitis is more likely to be painful, erythematous, and warm.

Elbow Instability

Ulnar Collateral Ligament Insufficiency

The UCL is the major restraint to valgus instability.

Injury is particularly common in throwing athletes because of repetitive valgus loading.

Valgus Stress Test

The elbow is flexed to approximately 30° to reduce bony stability, and a valgus force is applied.

The examiner palpates the UCL from the medial epicondyle to its insertion on the sublime tubercle of the proximal ulna.

Increased medial joint opening or absence of a firm endpoint suggests UCL insufficiency.

Additional UCL Tests

Other useful provocative maneuvers include the milking maneuver and moving valgus stress test.

These tests may reproduce medial elbow pain or demonstrate valgus instability.

Lateral Collateral Ligament Insufficiency

Lateral ligament failure may produce posterolateral rotatory instability of the elbow.

Posterolateral Rotatory Instability Test

The patient is positioned supine with the shoulder elevated overhead.

The humerus is stabilized, and the forearm is placed in full supination.

Starting with the elbow near extension, the examiner slowly flexes the elbow while applying axial loading and a slight valgus and supination force.

Positive Test

A positive test may produce a palpable clunk, posterior prominence of the radial head, and skin dimpling proximal to the radial head as the radiocapitellar and ulnohumeral articulations transiently subluxate.

Additional Instability Tests

Other maneuvers include the chair push-up test, stand-up test, and tabletop relocation test.

These reproduce symptoms by loading the elbow in positions that provoke posterolateral instability.

Valgus Extension Overload

Valgus extension overload is most commonly seen in overhead throwing athletes.

Patients may describe a painful pop or posteromedial discomfort during throwing.

Associated Abnormalities

The condition is frequently associated with UCL insufficiency, intra-articular loose bodies, and radiocapitellar cartilage injury.

Pathomechanics

Repeated throwing produces valgus stress medially, compression of the radiocapitellar joint laterally, and posteromedial impingement of the olecranon against the medial trochlea during terminal extension.

Examination

Passive forced hyperextension may reproduce posteromedial elbow pain.

Elbow Arthritis

Elbow arthritis commonly presents with loss of extension and pain at terminal extension.

Some patients also lose flexion as disease advances.

An effusion may or may not be present.

Flexion Contracture

Both active and passive extension may be restricted, resulting in a flexion contracture.

Mechanical impingement from osteophytes may contribute to terminal-motion pain.

Cubital Tunnel Syndrome

Cubital tunnel syndrome results from compression or traction of the ulnar nerve around the elbow.

Patients commonly report medial elbow discomfort together with numbness or paresthesias involving the ring and small fingers.

Symptoms are often aggravated by prolonged elbow flexion.

Tinel Sign

Percussion over the ulnar nerve posterior to the medial epicondyle may reproduce radiating paresthesias into the ulnar forearm and hand.

This represents a positive Tinel sign.

Additional Cubital Tunnel Tests

Other provocative maneuvers include the elbow flexion test, scratch collapse test, and shoulder internal rotation test.

The ulnar nerve should also be assessed dynamically for subluxation over the medial epicondyle during flexion.

Distal Biceps Tendon Rupture

A distal biceps rupture may present with acute antecubital pain, bruising, weakness, and loss of normal tendon palpability.

Supination weakness is often particularly pronounced.

Palpation

The distal biceps tendon may be absent or difficult to palpate within the antecubital fossa.

Tenderness is common in the acute setting.

Popeye Deformity

Retraction of the biceps muscle may produce a characteristic Popeye appearance.

A similar deformity can also occur with proximal biceps tendon rupture, so the location and mechanism must be considered.

Hook Test

The hook test is a useful examination for distal biceps integrity.

With the shoulder abducted and the elbow flexed approximately 90°, the patient actively supinates the forearm.

The examiner attempts to hook a finger beneath the distal biceps tendon from the lateral side.

Interpretation

In an intact tendon, the examiner can hook beneath the taut distal biceps.

Failure to palpate or hook the tendon strongly suggests a complete distal biceps rupture.

Biceps Squeeze Test

The patient’s elbow is flexed while the forearm is relaxed.

The examiner compresses the biceps muscle belly.

With an intact tendon, squeezing the muscle produces passive forearm supination.

Failure of the forearm to supinate suggests distal tendon rupture.

Passive Pronation-Supination Test

With the elbow supported at approximately 90° of flexion, the examiner palpates the biceps while passively pronating and supinating the forearm.

An intact tendon produces visible or palpable movement of the biceps muscle belly as the radius rotates.

Loss of this normal excursion may indicate tendon disruption.

General Examination Principles

Elbow pathology frequently overlaps with disorders involving the shoulder, cervical spine, forearm, wrist, and peripheral nerves.

A complete examination should therefore integrate inspection, palpation, range of motion, strength, neurologic assessment, stability testing, and condition-specific provocative maneuvers.

Comparison with the opposite elbow is particularly useful when assessing motion, carrying angle, strength, and ligamentous laxity.