Plica syndrome (also known as synovial plica syndrome) is a condition which occurs when a plica (an extension of the protective synovial capsule of the knee) becomes irritated, enlarged, or inflamed.he most common location of plica tissue is along the medial (inside) side of the knee. The plica can tether the patella to the femur, be located between the femur and patella, or be located along the femoral condyle.