The presence of a plica within the knee is felt to be a throw back to embryonic development of the knee. In utero the knee is divided initially by synovial membranes into 3 separate compartments. By the third or fourth month of fetal life, the membranes are resorbed, and the knee becomes a single chamber. If the membranes resorb incompletely, various degrees of septation may persist. These embryonic remnants are known as synovial plica. Synovial plica are normal structures found in many knees. Under normal circumstances, they are not associated with any painful conditions.
Types of patella plica
Four types of synovial plica of the knee have been described in the literature.
The suprapatellar plica divides the suprapatellar pouch from the remainder of the knee. The incidence of suprapatellar plica in a knee is 11%; however, one study reported a rate of 89% on autopsy.
The mediopatellar plica is the most frequent cause of plica syndrome. medial plica are found in 18-60% of normal knees
The lateral synovial plica is rare. Incidence of this kind of plica is less than 1%.
The infrapatellar plica is the most commonly encountered plica. This is not considered to be responsible for plica syndrome. It is not associated with a plica syndrome. Dupont found some type of inferior plica in 65% of their 200 dissected cadaveric knees.
Not all synovial plicae are symptomatic. For those that are, the etiology may not always be apparent. Inflammation leads to edema, thickening, and decreased elasticity of the plica. The plica may develop irregular edges and may snap over the femoral condyle, leading to a secondary synovitis and chondromalacia.
Normal plica are soft, wavy, and vascular with synovial-covered edges. pathological plica are thick, fibrotic, white, and inelastic.
Reported symptoms include anterior or anteromedial knee pain; intermittent or episodic pain; clicking; high-pitched snapping; occasional giving way; locking (really pseudolocking) and catching; and aggravation of symptoms by activity, by stair climbing, or by prolonged standing, squatting, or sitting.
On physical examination, the patient typically has tender points along the medial and inferior aspect of the patella,