Plica syndrome is a pathologic process due to inflammation of synovial plicae. Synovial plicae are frequently asymptomatic, but can become diseased with trauma and overuse. Synovial plicae are embryologic remnants of the synovial lining of the knee. The mechanism of their existence is controversial. Many agree that plicae are vestigial septums that once separated the knee joint into three cavities during embryogenesis. A second theory details a failure to resorb the mesenchyme that once occupied the knee joint during cavitation. The variable morphology of plicae can present as suprapatellar, infrapatellar, lateral and mediopatellar, with the latter most commonly progressing to plica syndrome. Synovial plicae remain an interesting challenge to clinicians, as plica syndrome is a common condition with a wide differential diagnosis. Many physical examination techniques can be used in conjunction with a thorough history to elucidate the presence of plica syndrome. The diagnosis is made by exclusion, therefore a multitude of imaging modalities are necessary to rule out other causes of knee pain. Conservative treatment is recommended initially, however, its effectiveness is variable. Surgical intervention is a robust method for treating plica syndrome when conservative treatment fails. This brief review provides an overview of knee embryogenesis, pertinent information regarding the etiology and pathology of plica syndrome, as well as insight into the diagnosis and management of this condition.