Citation, DOI and article data
Synovial folds or synovial plicae are remnant duplications of synovium formed during embryonic development.
The term ‘plica’ is commonly used if a synovial fold becomes symptomatic or a source of pain 1.
Normal synovial folds are thin and have a pliable consistency with a semitranslucent pinkish appearance 1. They are continuous with the joint capsule and project into the joint space at specific locations.
Synovial folds are described in the following joints and locations 1-4:
- synovial plicae of the knee
- synovial folds of the elbow
- synovial folds of the hip
- atlantoaxial joints
- cervical and lumbar spine facet joints
- shoulder joint
- posterior synovial fold: considered a normal variant 4
- septum between the subacromial and subdeltoid bursa: a possible rare cause of shoulder impingement
- ankle plica (rare)
- spanning anteriorly across the ankle joint
- originates in the anterolateral gutter from the osteocartilaginous fossa of the lateral malleolus
- blends with the soft tissue of the anteromedial gutter
- wrist and scaphotrapezial joint (rare)
- temporomandibular joint (uncertainty about their role in symptoms)
Functions of synovial plicae include the following 2,3:
- production of synovial fluid and lubrication of articular surfaces
- transition and accommodation of neurovascular structures
- space-filling and joint stabilization
Histologically synovial folds are composed of the synovial membrane with an underlying layer of loose connective tissue containing capillaries and venules 1.
There are different morphologic variants including band-like, leaf-like or villous synovial folds 2-4.
On MRI synovial folds appear as hypointense meniscoid or band-like structures surrounded by synovial fluid. They may be better visualized in the setting of a joint effusion.
- T1: isointense
- T2: low signal intensity
- PDFS/T2FS: low signal intensity
Synovial folds or plicae may be nicely visualized by CT/MR arthrography and usually appear as low signal intensity soft tissue bands or shelf-like structures within the brightly stained joint fluid. However, they might display normal morphological variations 4,5.
Synovial folds or plicae can become a cause of pain as a result of impingement and/or chronic inflammation due to repetitive stress, direct trauma or chronic inflammatory conditions 2.
- 1. Wong J & Lalam R. Plicae: Where Do They Come from and When Are They Relevant? Semin Musculoskelet Radiol. 2019;23(5):547-568. doi:10.1055/s-0039-1693979
- 2. Bencardino J, Kassarjian A, Vieira R, Schwartz R, Mellado J, Kocher M. Synovial Plicae of the Hip: Evaluation Using MR Arthrography in Patients with Hip Pain. Skeletal Radiol. 2011;40(4):415-21. doi:10.1007/s00256-010-1024-z
- 3. Webb A, Collins P, Rassoulian H, Mitchell B. Synovial Folds - a Pain in the Neck? Man Ther. 2011;16(2):118-24. doi:10.1016/j.math.2010.11.004
- 4. Ogul H, Tuncer K, Kose M, Pirimoglu B, Kantarci M. MR Arthrographic Characterization of Posterior Capsular Folds in Shoulder Joints. Br J Radiol. 2019;92(1094):20180527. doi:10.1259/bjr.20180527
- 5. Blankenbaker D, Davis K, De Smet A, Keene J. MRI Appearance of the Pectinofoveal Fold. AJR Am J Roentgenol. 2009;192(1):93-5. doi:10.2214/AJR.08.1363