Embryology:
Embryologically, knee is divided into 3 compartments by synovial membranes. By 3-4 month of embryonic life, the membranes are resorbed. The embryonic remnants are known as synovial plicae.
Types:
1. Infrapatellar plica (ligamentum mucosum): Most common (65%), least symptamatic; Originates in intercondylar notch and attaches to infrapatellar fat pad;
2. Suprapatellar plica: 2nd most common (55%), may cause suprapatellar bursitis or chondromalacia. Can be complete or incomplete. Courses from anterior femur or quadriceps tendon medially. Usually seen proximal to superior pole of patella.
2. Medial patellar plica - most frequent cause of plica syndrome, but least common (25%)4. Seen medially, courses obliquely downwards to insert on infrapatellar fat pad. Lies in coronal plane.
3. Lateral synovial plica - rare. Wider and thicker than medial plica. Inserts to lateral patellar facet.
Plica syndromes:
Cause of anteriomedial knee pain
TARP sign - Taut Articular band Reproduces Pain
History of blunt or twisting trauma
Palpable or audible snap or clicking
MR:
Normally the plica thickness is 1-2 mm
Symtomatic plica are more than 2 mm - 10 mm thick
May be torn rarely
Associated with erosion of patellar and medial femoral cartilage
References:
1.Resnick et al. Internal dergangements of joints. 2nd edition. Saunders Elsevier. 2007
