A plica is a ribbon-like fold of joint lining (synovium) which may be present in any knee as an embryological remnant.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

ligamentum mucosus
In this illustration, the capsule of the knee has been opened up to show the inner surface (synovium) and several folds which are frequently present - the various plicae (plural) of the knee.



A plica is a normal structure

A plica is something one is born with, and it may never give cause for concern. Sometimes, however, it may start to cause symptoms, perhaps after being traumatised and becoming a bit inflamed and thickened. Then it may become nipped between the moving structures of the knee, commonly the femur and patella, and cause intermittent pain.

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Symptomatic plicae often mimic other conditions

Plicae are normal anatomical structures, so they are often ignored when the surgeon is investigating the problematic knee. They may cause clicking and catching and be mistaken for a meniscus problem, for example. But usually a careful arthroscopic examination will reveal thickening at areas that are being impinged or a bit of redness and some damage to underlying joint cartilage.

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Peer-reviewed papers

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synovial plica
plical fold
plical remnant

Dr Sheila Strover (Editor)
BSc (Hons), MB BCh, MBA

See biography...


Also relevant -

Interesting course

Dr Thomas Smallman2017 - An alternative viewpoint on Anterior Knee Pain - by Dr Thomas Smallman (Knee Surgeon)

More material -


eBook about plica problems in the knee

eBook - An overview of plica problems in the knee

An expert look at the various plical folds of the knee and the problems that can be caused by a troublesome plica.

by Dr Lars Blønd (Knee surgeon)