A synovial plica is an infold of the joint lining or synovium - it is a normal anatomical structure but can sometimes become problematic.

ligamentum mucosus

The filmy band is actually a fold in the capsule of the knee, but that is not appreciated in this illustration.

synovial plica being nipped

This illustration gives a better example of how the plica folds in from the capsule surrounding the knee joint.


What causes a plica to become symptomatic?

If a plica is traumatised, it may become inflamed and eventually thickened, when it may be nipped between the bones of the knee causing sharp pain because the synovium itself is filled with pain-sensitive nerves.

Plica synovialis
An article about plica surgery in the knee based upon a forum discussion.

A list of references relating to the plica syndrome

What is the Plica Syndrome?

The plica syndrom is an often-missed cause of symptoms around the kneecap.


Part 7 of a course on Diagnostic Arthroscopy by Dr (Mr) Angus Strover

Medial plica

Plicae are often neglected as a cause of knee pain.




Synovial Plica Syndrome of the Knee: A Commonly Overlooked Cause of Anterior Knee Pain. Lee et al. Surg J (N Y). 2017 Jan; 3(1): e9–e16.

Synovial Plicae in the Knee Boles CA and Martin DF. American Journal of Roentgenology. 2001;177: 221-227.

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