In common with other synovial hinge joints, the relatively weak articular capsule is reinforced by strong collateral ligaments. The medial collateral ligament fans out from the medial epicondyle, where it is closely related to the common flexor tendon and primarily resists valgus stresses. The lateral collateral ligament is a strong triangular band fanning out from the lateral epicondyle, where it underlies and shares a close anatomical relationship with the common extensor tendon. It runs on to blend with the annular ligament below. The radial collateral ligament stabilizes the radial head, preventing varus stresses, and the annular ligament stabilizes the superior radioulnar joint. The elbow joint has two axes of motion and thus a greater inherent stability than the shoulder (Miyasaka 1999).

The capitulum is roughly hemispherical in shape and articulates with the radial head. The trochlea is pulley- or spool-shaped and extends from the anterior aspect of the distal end of the humerus to the olecranon fossa posteriorly. Its prominent medial ridge provides a valgus tilt which contributes to the carrying angle of the elbow joint. It articulates with the trochlear notch of the ulna.

On the distal anterior surface of the humerus sit the radial and coronoid fossae, accommodating the rims of the radial head and coronoid process of ulna in full flexion. The olecranon fossa of the humerus accepts the olecranon process of the ulna in full extension. The proximal end of the radius consists of a head, neck and tuberosity. The radial head is cup-shaped superiorly for articulation with the capitulum. The periphery of the head is an articulating surface for the superior radioulnar joint, articulating with the inner surface of the annular ligament. The radial tuberosity gives insertion to the biceps tendon.

At the proximal end of the ulna is the massive, hook-shaped olecranon process. Anteriorly, the coronoid process arises with the radial notch on its medial side for articulation with the radius at the superior radioulnar joint. The elbow joint itself permits flexion and extension coupled with a small amount of adjunct rotation (Standring 2009). About 160° of passive flexion exists as the bones become almost parallel and the radial and coronoid fossae allow for extra functional movement by accommodating the flexor muscle bulk. The normal end-feel of elbow flexion is soft due to approximation of the flexor muscles. Passive extension is achieved by locking the olecranon into the olecranon fossa; it corresponds to a 180° angle and has a hard end-feel due to bone contact.

The elbow joint receives a nerve supply from the musculocutaneous, median and radial nerves anteriorly, and the ulnar and radial nerves posteriorly (C5–C8).

The superior (proximal) radioulnar joint is a uniaxial pivot joint permitting the movements of pronation and supination. These movements occur between the circumference of the radial head in the fibro-osseous ring created by the annular ligament and the radial notch of the ulna. The annular ligament is covered internally by a thin layer of articular cartilage.

Movement occurring at the superior and inferior radio-ulnar joints is rotation of the radius around the ulna to produce pronation and supination. The range of passive pronation is approximately 85° and passive supination 90°, normally with an elastic end-feel.

The carrying angle (cubitus valgus) is evident in the anatomical position. The medial end of the distal humerus projects more distally and anteriorly than the lateral, pushing the ulna laterally to produce this valgus angle. It is approximately 10–15° in men and 20–25° in women (Palastanga et al 2006). Miyasaka (1999) cites several references suggesting that the carrying angle in women is 13–16° and noting that one large study demonstrated no difference in the carrying angle between men and women.

The cubital fossa is situated on the anterior aspect of the elbow. Its proximal border is an imaginary line drawn between the two epicondyles of the humerus; its lateral border is brachioradialis and its medial border is pronator teres. On the floor of the fossa lies supinator and biceps and the roof is formed by the overlying skin and fascia. The contents of the cubital fossa, from lateral to medial, are the tendon of the biceps in the centre, the brachial artery and the median nerve.

Biceps brachii (musculocutaneous nerve C5–C6) has two heads of origin. The muscle ends in a stout tendon which attaches deeply to the posterior aspect of the radial tuberosity. As the tendon passes to its insertion it twists so that its anterior surface comes to rest laterally. The tendon is separated from the anterior aspect of the radial tuberosity by the subtendinous bicipital bursa. The bicipital apo-neurosis arises anteromedially from the distal end of the tendon and sweeps medially to blend with the antebrachial fascia. Biceps is a powerful elbow flexor. Its secondary action, due to its insertion on the medial aspect of the radius, is to assist supinator in supination of the forearm, particularly with the elbow joint in 90° of flexion; it has no supinating action in the extended elbow.

Brachialis (musculocutaneous nerve C5–C6) takes origin from the anterior aspect of the lower half of the shaft of the humerus and inserts into the coronoid process of the ulna. As it crosses the elbow joint some of its deep fibres insert into the capsule of the elbow joint. Its action is to flex the elbow in either pronation or supination.

Brachioradialis (radial nerve C5–C7) passes from a long attachment on the upper two-thirds of the lateral supracondylar ridge of the humerus to the distal end of the radius just above the styloid. It flexes the elbow, being most effective in the mid-pronation–supination position.

Triceps (radial nerve C6–C8) has three heads of origin above the elbow, with its tendon inserting into the olecranon process. It is the main elbow extensor and is involved in pushing and thrusting activities as well as raising body weight on semiflexed elbows, as in getting up from a chair.

Extensor carpi radialis longus and brevis extend the wrist and produce radial deviation. They work synergistically with the finger flexor tendons by holding the wrist in extension, allowing the finger flexors to form an effective grip (Palastanga et al 2006).

Other muscles which share the origin from the common extensor tendon with extensor carpi radialis brevis and are also responsible for wrist extension are extensor digitorum, extensor digiti minimi and extensor carpi ulnaris (which also produces ulnar deviation). All of these muscles are supplied by the posterior interosseous nerve (C7–C8).

Flexor carpi radialis (median nerve C6–C7) arises from the medial epicondyle via the common flexor tendon and becomes tendinous above the wrist, before passing through its own lateral compartment under the flexor retinaculum. It inserts into the bases of the second and third metacarpals.

Palmaris longus (median nerve C7–C8), often absent, arises from the medial epicondyle via the common flexor tendon and passes over, not under, the flexor retinaculum, attaching to the distal flexor retinaculum and the palmar aponeurosis.

Flexor digitorum superficialis (median nerve C7–C8, T1) lies in a slightly deeper plane than the above flexor muscles and has a humeral head from the medial epicondyle via the common flexor tendon and a small radial head. It divides to pass under the flexor retinaculum before entering the fingers to attach to the middle phalanx of each.

Flexor carpi ulnaris (ulnar nerve C7–C8) has two heads of origin: a small humeral head from the medial epicondyle via the common flexor origin and an ulnar head from the ulna. It passes over the retinaculum into pisiform.

Palpate the lateral supracondylar ridge, which is a sub-cutaneous sharp ridge, giving part origin to extensor carpi radialis longus and brachioradialis.

The lateral supracondylar ridge terminates in the lateral epicondyle, a small bony projection which you will palpate more easily if the elbow is flexed.

Visualize the small facet on the anterolateral aspect of the lateral epicondyle which gives origin to the common extensor tendon of the superficial wrist extensor muscles. This facet is approximately the size of the patient’s little finger nail. This appears to impose a mechanical dis-advantage, since large forces are transmitted through the common extensor tendon to this small site, leading to possible strain. The area may also be vulnerable to shearing stresses during all movements of the forearm.

Palpate the head of the radius on the lateral side of the extended forearm; it is located in a posterior depression just distal to the lateral epicondyle. Confirm the correct position by rotating the forearm to feel the radial head move under your finger.

Move proximally a short distance to palpate the radiohumeral joint line, just above the radial head. It can also be palpated by dropping into the dimple on the posterolateral aspect of the olecranon. The gap between the head of the radius and the capitulum of the humerus should be obvious; flex your elbow and feel the joint open, providing the most accessible point for an intra-articular injection. Flexion past 45° tightens the joint capsule, making the joint line less obvious. Identify brachioradialis, the most superficial forearm muscle on the lateral side of the forearm, by flexing the elbow against resistance in the mid-pronation–supination position.

Palpate the medial supracondylar ridge which ends in the rounded knob of the medial epicondyle. Identify the medial epicondyle, which is subcutaneous and most easily felt with the elbow in extension. Palpate the anterior aspect of the medial epicondyle, which provides the attachment for the common flexor tendon of the superficial wrist flexor muscles.

Visualize the position of the superficial wrist flexor muscles by placing the thenar eminence of one hand onto the opposite medial epicondyle, and spread the digits down the forearm to represent the following tendons (Fig. 6.3):

It is not possible to palpate the joint line of the elbow anteriorly because of the position of the flexor muscles, but it can be visualized approximately 1 cm below the elbow flexor crease that connects the medial and lateral epicondyles (Miyasaka 1999, Palastanga et al 2006).

Locate the tuberosity of the radius by flexing the elbow to make the tendon of the biceps more obvious. Follow the tendon down to its insertion onto the radial tuberosity. The tendon of the biceps will be easily palpable as it passes deep into the cubital fossa, but the tuberosity may not feel distinct to the palpating finger, although it is tender to deep palpation.

Place the arm in the anatomical position of elbow extension and supination and note the obvious valgus angle, known as the carrying angle. It should be symmetrical bilaterally.

Palpate the proximal surface of the olecranon process, the point of the elbow that is subcutaneous and most easily palpated when the elbow is flexed. The olecranon gives insertion to triceps and a subcutaneous bursa, the olecranon bursa, lies under the loose skin at the back of the elbow.

The onset of the symptoms may be sudden, due to trauma, or gradual, due to overuse or arthritis. If the onset is traumatic in nature the mechanism of injury should be deduced. Acute injuries include dislocations and fractures of the radial head, olecranon and distal humerus (Safran 1995).

Hyperextension injuries may cause a capsulitis, or a fall on the out-stretched hand may cause fracture (e.g. supracondylar, distal radius or ulna) and/or dislocation. Possible neurovascular complications, secondary to trauma, should be kept in mind.

A sudden onset of pain associated with locking of the elbow could indicate a loose body.

The duration of the symptoms may be long-standing. The most common lesions at the elbow are due to chronic overuse and result in the enthesiopathies of tennis elbow (lateral epicondylar tendinopathy) and golfer’s elbow (medial epicondylar tendinopathy). The common tendons of the forearm flexors and extensors are susceptible to excessive use because they function across two joints. The causative factors may be intrinsic overload, from the force of muscle contraction; extrinsic overload, through excessive joint torque forces stressing the connective tissue, stretching and eventually disrupting it; or a combination of intrinsic and extrinsic forces (Safran 1995).

These overuse injuries are often associated with the middle-aged racquet sports player or individuals participating in throwing activities. Throwing motions may produce a valgus stress on the medial elbow and compressive forces at the lateral elbow. Such repetitive actions may result in microtrauma to the joint or surrounding tissues (Nicola 1992).

Climber’s elbow affects brachialis, as climbing involves the use of the semi-flexed pronated forearm (Safran 1995). Overuse may cause friction between the radial tuberosity and the biceps tendon, resulting in inflammation of the biceps subtendinous bursa, or an overuse lesion in the tendon itself.

The duration of symptoms indicates the stage of the lesion in the inflammatory process and will also give an indication for the likely length of treatment, with more chronic lesions usually taking longer to resolve. The common presentation of tennis or golfer’s elbow is pain of weeks’ or even months’ duration, while the less common loose body has recurrent episodes of twinging, often resolving spontaneously. Arthritis is characterized by recurrent episodes of exacerbation of symptoms and has usually been present for months or years.

The symptoms and behaviour need to be considered. The behaviour of the pain indicates the nature of the lesion: mechanical lesions are eased by rest and aggravated by repeated movements, particularly those involved in the mechanism of the lesion. For example, tennis elbow gives an increase of pain on gripping activities – simple things such as lifting a cup or pulling up bedclothes. Patients often report that knocking the lateral aspect of the elbow can give excruciating pain and it is very tender to touch. Other symptoms described by the patient could include twinges of pain with locking of the elbow, usually just short of full extension, which would indicate a possible loose body. A twinge of pain in the forearm on gripping is also associated with a tennis elbow, causing the patient to drop the object and giving an apparent feeling of muscle weakness.

Since the elbow is a peripheral joint, the joint is palpated for signs of activity. Heat indicates an active inflammation (Fig. 6.4), as does synovial thickening which is most easily palpable over the radial head in the more chronic state (Fig. 6.5). Swelling is usually most apparent in the dimples at the back of the elbow and may be palpated in that area. Other swellings such as that associated with olecranon bursitis or nodules can also be palpated to assess whether they are hard or soft.