Suprapatellar synovial fold

The suprapatellar synovial fold is a thin, synovial membrane remnant located in the suprapatellar region of the knee joint. It represents a residual portion of the embryonic suprapatellar septum, which initially separates the knee joint cavity from the suprapatellar bursa during fetal development. In adults, this fold is typically found medially and is considered one of several anatomical variants of the suprapatellar septum, specifically the "residual septum" type. It should not be used synonymously with the term "suprapatellar plica," as the fold is only one of four possible septal variants described in anatomic studies.

Histologically, the suprapatellar synovial fold consists of a synovial layer, an underlying collagenous layer, and may include an adipose component. It is generally asymptomatic but can occasionally contribute to knee symptoms if it becomes pathologically thickened or impinges on adjacent structures.