Synovial plicae are normal remnants of the synovial membrane in the knee joint that are usually asymptomatic. There are many types of infrapatellar plica (ligamentum mucosum):

• absent fold between the femoral condyles.

• complete synovial fold separate from the anterior cruciate ligament.

• split synovial fold separate from the anterior cruciate ligament but is further divided into 2 more folds.

• vertical septum attached to the anterior cruciate ligament that divides the joint into medial and lateral compartments.

• vertical septum with a defect or hole.