SYNOVITIS MRI FINDINGS KNEE WHAT DOES IT LOOK LIKE

Synovitis can take many forms on MRI — recognise the pattern once and you will spot it in any joint

▾ Normal Appearance

Normally you cannot differentiate synovium from capsule — what we see is a thin, low-signal line.
Best assessed on T2/PD sequences.

▾ Frond-Like Thickening

The most common appearance — thin, fibrillary morphology, intermediate signal on T2 and PD.
Much easier to detect on T2/PD than on T1.

▾ Nodular

Thicker appearance than frond-like synovitis — can be elongated or rounded and nodular.
Nodular synovitis should raise the possibility of PVNS (pigmented villonodular synovitis).

▾ Sheet-Like

More extensive synovitis with a solid, sheet-like morphology rather than discrete fronds or nodules.

▾ Confluent Capsular Thickening

▾ Localised Synovitis

Intermediate-signal synovitis confined to a specific area — commonly posterior to the meniscus.
Often associated with a meniscal tear, which is the likely cause of the localised synovitis in that region.

Synovitis presents as frond-like (most common), nodular, sheet-like, confluent capsular thickening, or localised — each with a distinct MRI morphology.
All types are best assessed on T2/PD sequences; T1 is much less sensitive.
Nodular synovitis should raise the possibility of PVNS.
Confluent capsular thickening is a form of arthrofibrosis, most often seen post ACL repair, and is typically low signal on PD/T2.
Inflammatory and infective synovitis cannot be distinguished on MRI — contrast enhances all forms equally and does not assist differentiation.