Table 3.

Anatomical features, prevalence and incidence of the synovial plicae

	IPP	SPP	MPP	LPP
Origin/localization	Femoral origin, intercondylar fossa in front of the anterior and lateral to the posterior cruciate ligament. It descends through the inferior joint space and proceeds as two fringelike alar folds to attach to the IFP	Between the suprapatellar pouch and the true knee	Originates in the suprapatellar region and passes inferiorly on the medial aspect of the knee joint before inserting into the IFP	Originates from the lateral aspect of the knee and inserts into the synovial membrane
Shape/Type	Five patterns: separated (cord‐like); split; vertical septum; fenestra; none of the above	Four types: I or septum completum, II or septum perforatum, III or septum residuale, IV or septum extinctum	Four types: A (cord‐like), B (shelf‐like), C D	–
Microscopic characteristics	–	Subsynovial adipose tissue with some dense collagen fibres, some skeletal muscle fibres	Adipose tissue with undulated regular collagen fibres	Subsynovial layer of areolo‐adipose tissue with collagen fibres
Prevalence	61–78.3%	33–89%	95%	20.7%
Incidence	85.5% with an age‐related decrease	Up to 91.2%	18–72%	<1%

IFP, infrapatellar fat pad; IPP, infrapatellar plica; LPP, lateropatellar plica; MPP, medial patellar plica; SPP, suprapatellar plica.