Synovitis refers to any inflammatory process affecting the synovium of joints and other structures lined with synovium such as tendon sheaths and bursae. It can take many morphological forms and occur from many etiologies. It may not necessarily be infective.
- infective synovitis / infectious synovitis
- non infective inflammatory synovitis
- degenerative conditions
- associated with the degree of cartilage loss
- associated with increasing symptoms and disease progression
- siderotic synovitis
- pigmented villonodular synovitis
- transient synovitis
- foreign bodies - foreign body induced synovitis
Syndromes associated with synovitis include:
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.
Synovitis can be well-visualized and assessed with ultrasound and MRI.
Ultrasound will usually show hypoechoic synovial thickening with increased vascularity on color or power Doppler in different graduations .
Suggested MR imaging for assessment of synovial disease include 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 show avid enhancement after contrast administration . Inflammatory activity is best reflected by early enhancement during dynamic imaging .
A relation between synovial inflammatory activity and the synovial volume and early enhancement has been shown .
- T1: hypointense
- T2: hyperintense
- T2FS/PDFS: hyperintense
- T1 C+ (Gd): homogeneous early enhancement