MRI has a key role in the diagnosis and assessment of inflammatory conditions of the wrist.

Its multiplanar capability, high contrast resolution and ability to assess for marrow inflammatory changes confers advantages over other modalities.

MRI has several important roles in the assessment of inflammatory conditions in the wrist and hand (1):

1) early diagnosis of inflammatory arthropathy

2) delineation of severity of arthropathy

3) monitoring of disease response to therapy

4) assessment of soft tissue inflammatory changes, such as tenosynovitis

Plain radiography, which allows delineation of bony erosions and joint space narrowing, was traditionally the mainstay of imaging in patients with rheumatoid arthritis and other inflammatory arthropathies. However, these changes occur late in the disease and represent irreversible damage.

Both MRI and ultrasound have several advantages over plain radiography for the early diagnosis of inflammatory arthropathy. This is important as early use of disease modifying anti-rheumatic drugs may prevent irreversible joint damage. MRI and ultrasound can assess inflammatory change in the synovium and delineate articular cartilage damage, and can identify bone erosions earlier than plain films.

The presence of focal subchondral oedema on MRI has also been shown to correlate with an increased risk of erosions (2). Synovial thickening can be difficult to differentiate from synovial fluid on MRI, as both may appear as high signal on T2 weighted images. Therefore, the use of intravenous gadolinium has been advocated to help distinguish synovial thickening from fluid. There is, however, very rapid diffusion of gadolinium into synovial fluid, particularly in inflamed joints, meaning that accurate assessment of synovial enhancement can only be performed in the first few minutes following injection. It is probably not crucial to distinguish between fluid and synovial thickening, as both are manifestations of the same inflammatory process, and both are often seen together. The total synovial volume, including both effusions and thickening, has been shown to correlate with symptoms and to be predictive of erosions.

On MRI, erosions appear as well-defined rounded subchondral lesions, containing synovial tissue or fluid only, and without the presence of marrow fat or trabecular bone (3). They are best demonstrated using a combination of T1 weighted and STIR or fat-suppressed images. Subchondral bone marrow oedema can usually be distinguished from erosions by its ill-defined feathery margins, which may be interspersed with areas of fatty marrow.

Accurate monitoring of disease status requires accurate and reproducible techniques for quantification, which is an area beset by difficulties. Synovitis, bone oedema and erosions on MRI have been defined by the Outcome Measures in Rheumatology Clinical Trials (OMERACT) group and a scoring system, termed the RA MRI score (RAMRIS), has been validated and evaluated for sensitivity to change in a longitudinal setting (4). The RAMRIS does not, however, include a scoring system for tendons or a score for cartilage loss.

Tendon pathology is often encountered in the wrist and hand, and may be the result of overuse, trauma or inflammation. The usual presentation is with pain and swelling. The nomenclature used to describe tendon pathology often leads to confusion. In recent years, the term tendinitis has lost favour as a term for describing tendon abnormality, as pathologically there is often no significant inflammatory change. A more accurate term is tendinosis, which describes a degenerative process with microtears and vascular in-growth. The term tendinopathy encompasses both degenerative and inflammatory phenomena. Tenosynovitis refers to inflammatory change within the tendon sheath, with or without morphological changes to the tendon.

With tendinosis, MRI may show thickening or thinning of the tendon, and there may be focal areas of increased T2 signal that represent myxoid degeneration. With tenosynovitis high T2 signal is seen to envelope the tendon. There may or may not be intrinsic tendon abnormality. MRI is more sensitive than ultrasound5. The presence of tendinopathy is a predictor for tendon rupture in rheumatoid arthritis.

De Quervain’s tenosynovitis is used to describe tendinosis and associated stenosing tenosynovitis affecting the tendons in extensor compartment one, namely the abductor pollicis longus and extensor pollicis brevis. These tendons are tightly secured to the radial styloid by an overlying extensor retinaculum. The retinaculum may impinge upon the tendons as a consequence of overuse. On MRI, thickening of the tendons can be appreciated, but there may be little or no change in signal characteristics.

Infection should always be considered in cases of acute inflammatory arthritis. Synovial proliferative disease such as pigmented villonodular synovitis (PVNS) should also be considered. The presence of haemosiderin deposition may be highly suggestive of PVNS. Certain tumours such as osteoid osteoma may also result in a marked inflammatory response.

MRI is superior to clinical examination in the detection of joint inflammation (6).

MRI can be used to improve the certainty of a diagnosis of RA above clinical criteria alone.

MRI bone oedema is a strong independent predictor of subsequent radiographic progression (i.e.erosions) in early RA and should be considered for use as a prognostic indicator.

Joint inflammation (synovitis) detected by MRI can be considered predictive of further joint damage.

Synovitis on MRI may be used to predict response to treatment and may be useful in monitoring disease activity