Synovial folds - Plicae synoviales
In some of the joints the synovial membrane is thrown into synovial folds which pass across the cavity; they are especially distinct in the knee. In other joints there are flattened folds, subdivided at their margins into fringe-like processes which contain convoluted vessels. These folds generally project from the synovial membrane near the margin of the cartilage, and lie flat upon its surface. They consist of connective tissue, covered with endothelium, and contain fat cells in variable quantities, and, more rarely, isolated cartilage cells; the larger folds often contain considerable quantities of fat.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).
General Anatomy > Joints; Articular system > Bony joints > Synovial joint; Diarthrosis > Joint capsule; Articular capsule > Synovial membrane; Synovial layer > Synovial folds