Plica is a remanant of synovial membranes. During embryonic life [fetal development], the knee is not a single chamber is divided into three separate compartments by synovial membranes. These membranes are resorbed by thitd or fourth month and knee becomes and the knee becomes a single chamber. Incomplete resorption of membranes may various degrees of septation. These embryonic remnants are known as synovial plicae.
Plica in Latin simply means a fold.
Types of Plicae
There are four types of synovial plicae of the knee.
It is also called plica synovialis suprapatellaris, and it divides the suprapatellar pouch from the remainder of the knee. The separation may be complete or incomplete.
The suprapatellar plica usually begins proximal to the superior pole of the patella but variations may occur in origin. From there, it courses from the anterior to femoral metaphysis or the posterior of quadriceps tendon to the medial wall of the joint.
The incidence of suprapatellar plica has been reported to be as low as 11% to 90%
Mediopatellar or Medial Plica
This plica, is also called as a shelf.
- Type A: A cord-like, thin elevation of the synovial wall, under the retinaculum.
- Type B: A narrow synovium, with a shelf-like appearance, which does not cover the anterior surface of the medial femoral condyle.
- Type C: A larger synovium, with a shelf-like appearance, which partially covers the medial femoral condyle.
- Type D: A type C plica that is fenestrated, creating tags
This classification has clinical significance. Types A and B are not likely to produce symptoms, while types C and D, due to their size, may become trapped and impinged between the patellofemoral joint.
It is the most common plica and is also called ligamentum mucosum. It is bell shaped remand nant originates in the intercondylar notch, widening through the anterior joint space, and attaches to the infrapatellar fat pad.
Most of the times, plicae are not symptomatic though their presence has been reported in 90% pepole undergoing arthroscopy . Infrapatellar plica may obscure portal entry sites or interfere with visualization during arthroscopy.
Suprapatellar plica may initiate a suprapatellar bursitis or chondromalacia, though it is controversial. 
- Sakakibara J. Arthroscopic study on linos band (plica synovia is mediopatellaris) J Jpn Orthop Assoc 1976; 50: 513–22
- Boles CA, Martin DF. Synovial plicae in the knee. AJR Am J Roentgenol. 2001;177 (1): 221-7
- Hodge JC, Ghelman B, O’Brien SJ et-al. Synovial plicae and chondromalacia patellae: correlation of results of CT arthrography with results of arthroscopy. Radiology 1993;186 (3): 827-31 [Abstract]
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