Plica Syndrome

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Original Editors - Nel Breyne

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Definition/Description

Plica allows movement of the bones of the joint without restriction. It is overused when you make the same movement to often, such as bend and straighten the knee.
Plica syndrome is an interesting problem that occurs when an otherwise normal structure in the knee becomes a source of knee pain due to injury or overuse. The diagnosis can sometimes be difficult, but if this is the source of your knee pain, it can be easily treated.

Clinically Relevant Anatomy

The knee joint has 3 synovial cavities: medial, infrapatellar and suprapatellar. These cavities are so called plica. Lateral plica is seen infrequently because the joint space on the lateral side is faster formed. The suprapattelar bursae is found as a slit between femur and quadriceps. With the knee joint it forms a perforation. When the perforations of the suprapatellar bursae are incomplete with the knee joint, it leads to the development of the suprapatellar plicae.

- Suprapatellar plicae
The suprapatellar plicae lies between the true knee and the suprapatellar pouch, it is seen as a synovial membrane. Arthroscopic studies shows an incidence of the plica between 70% and 91%. It’s easy to report the suprapatellar plica as completely absent, by carefully attempting identifying the insertion of the articulus genu, this confusion can be avoid. Indicate a complete type of plica when the insertion of the muscle is not to be seen. When you aren’t sure what type of plica, use the classification table.

Table 1. Classification of suprapatellar plica (Kim and Choe).
Type Description
Absent No sharp edged fold.
Vestigial Plica with less than 1 mm protrusion. Disappeared with external pressure
Medial Plica lying on the medial side of the suprapatellar pouch
Lateral Plica lying on the lateral side of the suprapatellar pouch
Arch Plica present medially, laterally and anteriorly but not over the anterior femur
Hole Plica extending completely across the suprapatellar pouch but with a central defect.
Complete Plica dividing the suprapatellar pouch into two separate compartments
(Kenta & Khanduja, 2009)

- Medial patella plica
Also known as the medial synovial shelf, plica synovialis mediopatellaris, and plica alaris elongata or after its first two descriptors as Iion's band or Aoki’s ledge. It attaches to the lower patella and the lower femur and can cross the suprapatellar plica to insert in the synovium surrounding the infrapatellar fat pad. Similar to suprapatellar plica, the medial plica has also a classification table by Kim and Choe.

Table 2. Classification of medial plicae (Kim and Choe).
Type Description
Absent No synovial shelf on the medial wall
Vestigial Less than 1 mm of synovial elevation which disappears with external pressure
Shelf A complete fold with a sharp free margin.
Reduplicated Two or more sheves running parallel. They may be of differing sizes.
Fenestra The shelf contains a central defect
High-Riding A shelf like structure running anterior to the posterior aspect of the patella, in a position where I could not touch the femur.
Each type is subdivided according to size and relation to femoral condyle with flexion and extension of the knee into: A—Narrow non touch (never makes contact with the femoral condyle). B—Medium touch (touches condyle with knee movement). C—Wide covering (covers the femoral condyle).
(Kenta & Khanduja, 2009)

- Infrapatellar plica
Also called as ligamentum mocosum. Just like the medial plica the infrapattelar plica inserts in the synovium around the infrapatellar fat pad. The infrapatellar plica has a relation with the anterior cruciate ligament, it can be totally separated from the plica or attached to it. Here’s also a classification table.

Table 3. Classification of Infrapatellar plicae (Kim and Choe).
Type Description
Absent No synovial fold between the condyles of the femur.
Separated A complete synovial fold that was separate from the anterior cruciate ligament (ACL).
Split Synovial fold that is separate from the ACL but is also divided into two or more cords.
Vertical septum A complete synovial fold tht is attached to the ACL and divided the joint into medial and lateral compartments.
Fenestra A vertical septum pattern that contains a hole or defect.
(Kenta & Khanduja, 2009)
 

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