Synovitis

Synovitis refers to any inflammatory process affecting the synovium of joints, tendon sheaths and bursae. It can take many morphological forms and occur from many etiologies. It may not necessarily be infective.

Pathology

Specific subtypes

• infective/infectious synovitis

• non-infective inflammatory synovitis

  • rheumatoid arthritis

  • psoriatic arthritis

  • ankylosing spondylitis

  • reactive arthritis

  • enteropathic arthritis

• degenerative conditions

  • osteoarthritis

    • common

    • associated with the degree of cartilage loss

    • associated with increasing symptoms and disease progression

• siderotic synovitis

• transient synovitis, e.g. transient synovitis of the hip

• foreign bodies, e.g. foreign body induced synovitis

Syndromes associated with synovitis include:

• SAPHO syndrome

Chronic synovitis causes pannus formation which is characterized histologically by hypervascular masses of villous hyperplasia, cellular infiltration and fibroblastic proliferation. Fibrosis is often the end result.

Radiographic features

Synovitis can be well-visualized and assessed with ultrasound and MRI.

Broad general features include synovial thickening (can take many forms), synovial enhancement and increased vascularity (e.g. on color Doppler ultrasound). An effusion may be present.

Ultrasound

Ultrasound will usually show hypoechoic synovial thickening with increased vascularity on color or power Doppler in different graduations ⁷.

MRI

Suggested MR imaging for assessment of synovial disease includes T1 weighted images before and after intravenous contrast as well as T2 weighted fat saturated or STIR images in at least two different planes.

In the setting of synovitis, the synovium will be thickened and irregular, sometimes frond-like, and show avid enhancement after contrast administration ^8,11. Inflammatory activity is best reflected by early enhancement during dynamic imaging ⁸.

A relation between synovial inflammatory activity and the synovial volume and early enhancement has been shown ^8-10.

Signal characteristics

• T1: hypointense

• T2: hyperintense

• T2/PD FS: hyperintense

• T1 C+ (Gd): homogeneous early enhancement

See also

• synovium

• synovial enhancement

• synovial hyperplasia

• arthritis