Musculoskeletal ultrasound (US) is a valuable imaging modality for detecting and quantifying a range of joint pathologies occurring in rheumatic diseases (1-2). In inflammatory arthritis and in osteoarthritis (OA) it is able to show early and late findings including cartilage lesions (1-4). Normal hyaline cartilage is imaged by US as a homogeneously anechoic layer lining the bony cortex and having a superficial and a deep margin that appear thin, sharp, continuous and regularly hyperechoic. In OA, loss of the anechoic echotexture, irregularities and loss of sharpness of the margins and progressive thinning of cartilage layer are visualized (1). With disease progression, focal and asymmetric narrowing is usually present up to the complete absence of the cartilaginous layer and cartilage breakdown (5). US has been demonstrated to be a reliable tool for assessing cartilage abnormalities in hand joints of OA patients (1).
In rheumatoid arthritis (RA) US detects loss of the sharpness of the cartilage margins, partial or full-thickness defects and complete loss of the cartilage with subchondral bone involvement (6).
In crystal arthropathy, the conformation and anatomical location of crystals at cartilage level help in differentiating gout and calcium pyrophosphate deposition disease (CPDD) (11). Hyperechoic enhancement of the superficial margin of the hyaline cartilage is visualized in gout and hyperechoic spots within the cartilage layer are imaged in CPDD. In gout, urate crystals deposit over the superficial margin of the cartilage (double contour sign) with focal or diffuse enhancement of the superficial cartilage margin, whose reflectivity is independent of the angle of insonation. In CPDD, pyrophosphate deposits are visualized within the cartilage layer and the double contour aspect is shown as a thin hyperchoic band with focal, punctate or diffuse features. High sensitivity, specificity and accuracy of US in detecting urate and pyrophosphate crystals deposits at knee cartilage level have been recently reported (11).
All cartilaginous changes need to be assessed by using a correct US scanning technique, based on appropriate patient positioning to allow the sonographic beam to penetrate the joint, adequate probe orientation to obtain perpendicular insonation of the US beam and assessment of the contralateral site to perform complete and deep comparisons (5).
Key messages: US detects a wide range of cartilage abnormalities in OA, RA and crystal related arthropathies. Mandatory technical aspects should be taken into account when assessing the hyaline cartilage (correct machine setting, multiplanar assessment, dynamic evaluation and comparisons with contralateral side) with limited applications to some anatomic areas, depending on the presence of appropriate acoustic windows.
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Keen HI et al. Can ultrasonography improve on radiographic assessment in osteoarthritis of the hands? A comparison between radiographic and ultrasonographic detected pathology. Ann Rheum Dis 2007
Iagnocco A et al. High resolution ultrasonography in detection of bone erosions in patients with hand osteoarthritis. J Rheumatol 2005
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Filippucci E et al. Interobserver reliability of ultrasonography in the assessment of cartilage damage in rheumatoid arthritis. Ann Rheum Dis 2010
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Filippucci E et al. Hyaline cartilage involvement in patients with gout and calcium pyrophosphate deposition disease. An ultrasound study. Osteoarthritis Cartilage 2009
Disclosure of Interest None Declared