The role of imaging modalities in the diagnosis, differential diagnosis and clinical assessment of peripheral joint osteoarthritis.

Peripheral joint osteoarthritis (OA) is predominantly a clinical diagnosis, though imaging may provide confirmation and aid with differential diagnosis where there is clinical doubt. Whilst radiographs (X-rays (XR)) are usually the first-line imaging modality selected, magnetic resonance imaging (MRI), ultrasound and computed tomography (CT) may all have a valuable role in assessing a person with OA, although each has its particular advantages and disadvantages. MRI is of particular use for diagnosing bone conditions that may cause a rapid increase in symptoms, such as avascular necrosis (AVN) or a subchondral insufficiency fracture (SIF), while providing concomitant soft tissue assessment. Ultrasound offers rapid assessment of peripheral joints and can easily assess for features of inflammatory arthritis. CT is faster to perform than MRI and can also image the subchondral bone, but does involve ionising radiation. Selecting the correct imaging modality, in the context of its advantages when visualising a specific joint (e.g., hand vs knee) and with clinical context in mind, will enhance the added value of imaging in clinical practice.