Chapter 15

### INTRODUCTION

The elbow joint is a hinge joint with a loose capsule and collateral ligaments. The capsule is situated along the anterior and posterior aspect of the joint, preventing flexion–extension movements, whereas the collateral ligaments prevent medial and lateral movements. The articulating bones include the distal humerus, proximal radius, and ulna. The medial humeral condyle, also known as the trochlea, articulates with the upper end of the ulna known as the coronoid process. The humeroradial part of the joint consists of the capitellum (distal humerus) and head of the radius.

The elbow joint is often subject to overuse injuries. Partial or complete tears of tendons such as the biceps tendon are not infrequent and are often an indication of magnetic resonance imaging (MRI) study. Nerve entrapment syndromes around the elbow are often diagnosed clinically and MRI is usually indicated to rule out a lesion that could be within the nerve or causing compression of the nerve. In this chapter, we will discuss some of the common conditions affecting the elbow joint.

### IMAGING PROTOCOL

All imaging should start with radiographs, including anteroposterior and lateral views of the elbow joint (Figure 15-1). While a bony injury might be evident on these views, when no obvious fracture line or misalignment is noticeable, one has to look at the soft tissues to see if there are secondary signs of insult, such as a “sail sign.” This is a triangular density of fat lifted into the field of view by the effusion in the elbow joint (Figure 15-2). There is controversy as to whether an anterior or posterior sail sign is more important. Any sign of a joint effusion, whether anterior or posterior, merits further investigation.

###### Figure 15-1.

Normal elbow. Lateral radiograph of the elbow. Note anterior stripe of fat is adjacent to the distal humerus.

###### Figure 15-2.

Sail sign. The fat overlying the joint capsule is lifted off due to distension of the joint capsule by joint effusion and appears as a triangular hypodensity proximal to the joint line (arrow).

In our institution, we routinely perform the following MR sequences: coronal T1-weighted, coronal short tau inversion recovery (STIR), axial T1-weighted, axial T2-weighted fat-suppressed, sagittal proton density (PD) weighted fat-suppressed, and sagittal T2-weighted sequences. Further sequences are tailored according to what is seen on initial imaging, and the benefits of using gadolinium (Gd) are weighed against the risks. If an ultrasound-guided biopsy is under consideration we require a Gd-enhanced T1-weighted fat-suppressed sequence to see if enough synovial tissue is visualized to merit an ultrasound-guided biopsy.

### EPICONDYLITIS

Pain at the origin of common flexor or extensor group of tendons is usually termed epicondylitis. ...

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