Osteoarthritis is best diagnosed with weight-bearing views (they are more sensitive than non-weight-bearing views). n Ultrasound: This has become a major imaging method in joint disease. It provides both static and dynamic images and allows focused multiplanar imaging. It is of great value for demonstrating joint effusions and synovitis. The most common ultrasound examinations performed are of the shoulder, hand, ankle and foot (9,13,14). n Computerised tomography (CT): This provides detailed information about bone but little about soft tissue. The ability to view the joint in multiple planes and produce three-dimensional models makes it very useful for radiological assessment and surgical planning (2,3) but is rarely used for primary diagnosis. n Magnetic resonance imaging (MRI): MRI is most commonly used for joint imaging. It provides information on both the soft tissues and bony components and is a very effective diagnostic tool for virtually all joint pathology. It has only limited value, however, in the presence of established osteoarthritis.

Arthrography This is a technique that allows further joint assessment. It involves injection of a contrast agent into the joint, which distends the joint and outlines the articular cartilage, revealing both bony and soft-tissue abnormalities. The joint is injected under image guidance, either via ultrasound or fluoroscopy, and is imaged either with CT or MRI (more commonly). It is useful for detailing cartilage defects, intra-articular bodies and damage to the ligaments and soft tissue structures such as the acetabular or glenoid labrum. This technique is used in the shoulder, wrist and hip (1,3,10).

Imaging the shoulder joint Due to its wide range of movement and complexity, the shoulder is one of the most difficult joints to image. The common indications for imaging are in shoulder impingement and suspected tears of the rotator cuff or glenoid labrum. n Plain radiograph: Initial assessment is often with plain radiographs. Two views are usually taken, an anteroposterior (AP) view and an axial view. In dislocations, the joint is seen

20 sportEX medicine 2010;44(Apr):18-23

SENSITIVITY OF IMAGING TECHNOLOGY MEANS PATHOLOGY CAN BE IDENTIFIED MUCH EARLIER

THE INCREASED SOPHISTICATION AND

Figure 3: Ultrasound image of a full-thickness tear of the supraspinatous tendon (arrowed) in a right shoulder.[cropped off data and text]

Figure 4: MR arthrography series of an axial tear (double black arrow) and biceps dislocation showing the subscapularis (white arrow).

to be incongruous and, depending on its position, an anterior and posterior dislocation can be diagnosed. Relocated shoulders need to be imaged to verify that the shoulder is back within the joint and to identify bony evidence of dislocations. The

bony Bankart lesion is a bony avulsion from the inferior margin of the glenoid, and it implies a labral tear of the glenoid. The Hill–Sachs lesion is a depressed fracture of the posterior part of the head of the humerus and can be a fulcrum for recurrent dislocations. Stress views of the acromioclavicular joint (ACJ) can also be performed to diagnose dislocations of the ACJ (2). n Ultrasound: Ultrasound is extensively used to assess the muscles and tendons surrounding the shoulder joint. The most common indication is painful arc syndrome with external impingement and calcific tendonitis, capsulitis and rotator cuff tears are the commonest diagnoses. The rotator cuff is assessed for tendinopathy and tears, and ultrasound has high sensitivity and specificity for identifying full-thickness rotator cuff tears (14) (Fig. 3). It can estimate the size of the tear and evaluate its suitability for surgical repair. Subacromial sub-deltoid bursitis can be visualised and dynamic ultrasound can demonstrate bursa impingement under the coraco-acromial ligament, and ultrasound-guided injections of the subacromial bursa can be performed at the same sitting. Ultrasound is used to assess the long head of the biceps and some of the shoulder ligaments such as the coraco-acromial and transverse humeral ligaments (14,15). n Computerised tomography: CT examination of the shoulder is relatively unusual. The main indication is imaging fractures around the shoulder either for preoperative planning or for diagnosis of a radiographically occult injury. CT arthrography can be used to evaluate labral tears in the shoulder but it has been largely superseded by MRI (3,4). n Magnetic resonance imaging: MRI is used relatively sparingly for