Key points

Introduction

The emphasis of this article is on the use of radiographs and MR imaging for the diagnosis of elbow disorders. For completeness, the authors have included discussion relating to other imaging techniques, including computed tomography (CT), ultrasound, and nuclear medicine where they are of clinical importance.

Radiographs have been the mainstay of initial imaging of the elbow, particularly in the trauma setting. In the absence of traumatic injury, most of the disease processes encountered in the elbow relate to the soft tissues. Ultrasound examination will then be performed prior to radiographs when soft tissue disease is suspected. MR imaging has the advantage over radiographs and ultrasound in accurately examining both bone and soft tissue.

This article concentrates on the use of radiographs and MR imaging when the patient presents with particular symptoms. Fractures and children’s abnormalities are covered in other articles.

General

Radiographs

Value

The value of conventional radiographs is that they typically clearly show fractures if at least 2 views of the affected area are undertaken. Furthermore, they are used in the initial assessment of bone pain as an examination to exclude bone tumors. They will demonstrate areas of lysis, calcification, and sclerosis within the bone. Bone textual changes may be observed including cortical scalloping and disturbance of the trabecular pattern of the medulla. Irregularity of the cortex may be seen in the enthesitis at the site of tendon insertion.

Displacement of fat pads in the soft tissues will identify larger joint effusions. Swollen soft tissues and calcification within the soft tissue may be observed. Fat-containing mass lesions may be seen as a radiolucent area within the soft tissue.

Limitations

A major limitation of conventional radiographs is that they are only a 2-dimensional image of a 3-dimensional object, and therefore abnormalities may be obscured by the overlying tissue. Microfracturing of bone will not be identified, and at least 80% of the bone must be destroyed before a radiograph will show a lucency when the destruction is centrally located. When there is cortical destruction, this will be identified sooner. This means that radiographs will not detect many cases of early cancer ( Figs. 1 and 2 ).

( A ) Radiograph of a giant cell tumor in the olecranon in a 12-year-old patient. ( B ) Sagittal STIR MR imaging of a giant cell tumor in the olecranon in a 12-year-old patient. ( C ) Axial T1 fast spin echo (FSE) MR imaging of a giant cell tumor in the olecranon in a 12-year-old patient.

( A ) Radiograph of an Aneurysmal bone cyst in the proximal radius. ( B ) Axial T2 FSE MR imaging showing fluid levels in an aneurysmal bone cyst in the proximal radius.

In addition, the contrast between different soft tissue types is low, thus reducing the sensitivity of diagnosis, meaning many soft tissue abnormalities cannot be identified by radiographs.

Lateral elbow pain

The causes of lateral elbow pain are given in Box 1 .

When a patient presents with pain on the radial side of the elbow, a radiograph is the initial investigation to exclude osteoarthritis of the radiocapitellar joint. This will be identified by the features including the presence of marginal osteophytes, irregular joint space narrowing, subchondral sclerosis, and subchondral cysts. In younger patients, there may be osteochondritis dissecans of the capitellum.

Calcification may be visible on the radiograph along the lateral epicondyle secondary to enthesitis. Please note that the presence of calcification is not limited to enthesitis; it can also be seen in soft tissue masses, including tumors and myositis ossificans and due to be calcification in an abnormal tendon ( Fig. 3 ).

( A ) Radiograph of a common extensor origin calcific tendinosis. ( B ) Coronal STIR MR imaging showing the same common extensor origin calcific tendinosis. ( B ) Coronal STIR MRI showing the same common extensor origin calcific tendinosis. The oedema in the common extensor muscle is likely to be secondary to an acute absorption of the calcification.

MR imaging may detect more subtle radiocapitellar osteoarthritis where there is cartilage loss and subchondral edema. The pseudodefect of the capitellum must be appreciated in the younger patient, and this can be misdiagnosed as an osteochondral fracture.

The pain may arise from the lateral tendon insertions. The most commonly affected tendon group is the common extensor origin (CEO), commonly called tennis elbow or lateral epicondylitis.

On MR imaging, the extensor digitorum communis, extensor digiti minimi, and extensor carpi radialis brevis tendons have a common origin on the superior aspect of the lateral epicondyle. On the posterior inferior aspect of the lateral epicondyle is the insertion of the extensor carpi ulnaris, and this is separated from the insertion of the anconeus by fat.

The common insertion of the radial collateral ligament and lateral ulnar collateral ligament on the superior aspect of the intertubercular sulcus and inferior aspect of the superior tubercle may also be identified.

Common extensor tendinosis occurs in patients who perform repeated extension of their wrists with gripping and supination. It is seen in novice tennis players because of poor backhand technique rather than in elite competitors (tennis elbow is never seen at Wimbledon). Interestingly, it is also more commonly seen in golfers than golfers’ elbow and is reported in around 85% of golfers. In golfers, the left elbow is affected in right-handed players and vice versa. The disease commences at the origin of the extensor carpi radialis brevis and as the disease progresses, tearing of the undersurface of this tendon occurs. This can sometimes lead to a more extensive tearing over time. This abnormality will be clearly seen by MR imaging but not on a radiograph. On an MR imaging fluid-sensitive sequence, the area of abnormality will be of high signal intensity because of mucoid degeneration of the tendon and/or tearing with fluid in the gap. If calcification is present, this will typically be of low signal on all sequences. There may be associated edema within the anconeus muscle. The anconeus muscle is thought to be a lateral stabilizer of the elbow blending with the lateral joint capsule and lateral triceps muscle. Avulsion injuries isolated to this muscle can therefore also be seen. MR signal changes within the CEO can be seen following a recent injection and in the asymptomatic patient; hence clinical correlation is advised.

The lateral collateral ligament is commonly thickened or torn when there is an extensive common extensor origin tendinosis, as it blends with the undersurface of the tendons.

Medial elbow pain

The causes of medial elbow pain are given in Box 2 .

Established osteoarthritis of the medial humeroulnar joint will be detected on radiographs by the same features as described for lateral elbow pain.

MR imaging may detect more subtle medial osteoarthritis when there is cartilage loss and subchondral edema. The pseudodefect of the trochlear transverse ridge is a pitfall in MR imaging interpretation.

Approximately 9.8% to 20% of epicondylitis relates to the common flexor origin. The pronator teres and flexor carpi radialis tendons insert on the anterior aspect of the medial epicondyle and are the most commonly affected. This is commonly known as golfers’ elbow or medial epicondylitis. It can also occur in other daily activities with repeated wrist flexion and protonation such as bowling, pitching, carpentry, and in the playing of stringed instruments. Radiographs may show traction spurs around the humeral medial epicondyle. It is best identified by MR imaging. The tendons do not commonly tear and if they do this usually occurs in combination with medial collateral ligament injury. Tendinosis will have similar appearances to common extensor origin tendinosis on MR imaging. Pronator teres muscle tears rarely occur when a bat or club hits the ground during a vigorous swing during cricket or golf, and flexor carpi ulnaris and digitorum superficialis muscle tears were observed at the London Olympic Games 2012

The ulnar collateral ligament (UCL) of the elbow can be injured in throwing athletes. This will be a cause of medial-sided elbow pain. It can be injured at the same time as the medial tendons. In the United Kingdom, this is most commonly seen in javelin throwers, but in the United States, baseball pitchers are more frequently affected. If there is a complete tear, a radiograph can demonstrate widening of the medial joint line. Any associated avulsion fractures with this injury will often be identified on a radiograph. Calcification may also be seen within an injured UCL on a radiograph. The ligament will become thickened and edematous and will be seen on a fluid-sensitive MR sequence as high signal intensity. The ligament can sometimes remain intact despite an avulsion fracture of the sublime tubercle of the coronoid process of the ulna and will be seen as a detached fragment of bone. For this, T1 spin echo sequences are useful.

The ulnar nerve is in close proximity to these other structures and can be injured concomitantly or be a cause of pain in itself. Ulnar nerve abnormalities will be discussed in more detail in the section on neurologic symptoms.

Snapping triceps syndrome is caused by the medial head of the triceps muscle dislocating over the medial epicondyle in elbow flexion beyond 100°. It can be congenital or acquired. Congenital problems include an accessory triceps tendon or hypoplastic bone. Acquired hypertrophic musculature in weightlifters can lead to snapping. This can be a cause of pain in itself, but it can also cause ulnar neuritis. There is no specific radiographic feature that relates to this diagnosis.