Synovial folds of the elbow
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Synovial folds, synovial plicae or synovial fringes of the elbow are structures found within the elbow joint. Their function remains unknown, however, there are theories that they might have a cushioning or load dispersing effect. Occasionally they can cause symptoms.
Like the synovial folds in other joints, elbow plicae are made up of fibroadipose tissue and fill a part of the space and non-articular indentations of the elbow joint. They are thought to be embryologic remnants and display multiple variations in form size and location 1-3.
They are contiguous with the capsule-ligament complex projecting into the joint space proximal of the annular ligament 1-4. A circumferential radiohumeral synovial fold is rarely present and has been described in up to 12% of cases 1,2. The following portions are more commonly found 1:
- posterolateral plica: in the posterolateral portion of the radiocapitellar joint near the pseudodefect of the capitellum with close relations to the anconeus muscle, lateral ulnar collateral ligament and common extensor origin
- lateral synovial fold: laterally between the lateral border of the radial head and the capitellum
- anterior synovial fold: anteriorly between the anterior of the radial head and capitellum
- lateral olecranon: located posteriorly in the lateral olecranon recess in close relationship to the anconeus muscle
The posterolateral portion of the radiohumeral synovial fold has been most commonly found on cadaver studies and imaging (86-98%) followed by the anterior synovial fold (67%). The lateral synovial fold is rarest and descriptions of the posterior synovial fold in the lateral recess of the olecranon are very variable (28-73%) 1,2.
On MRI, synovial folds appear as hypointense meniscoid bands surrounded by synovial fluid 1,2.
- T1: isointense
- T2: low signal intensity
- PDFS/T2FS: low signal intensity
On CT arthrography they can be seen as shelf-like bands protruding into the joint space 1,2.