Infrapatellar plica injury: Magnetic resonance imaging review of a neglected cause of anterior knee pain.

Synovial plicae are normal remnants of synovial membranes within the knee joint cavity and are usually asymptomatic. Pathological infrapatellar plica, which is mostly due to plica injury, may be a potential cause of anterior knee pain, but is often overlooked and under-reported on magnetic resonance imaging (MRI). This pictorial review illustrates the MRI findings of infrapatellar plica injury and associated knee injuries, with emphasis on its differentiation from the mimics of plica injury.