Synovial plicae of the knee

Abstract

Synovial plicae represent inward folds of the synovial lining of the knee joint capsule, which are considered vestiges of a membranous knee joint partition present during foetal development. Three such folds are found with regularity in the human knee, but most are asymptomatic and of little clinical consequence. Plicae are more commonly seen in young adults, and can be an important cause of anterior knee pain, presenting with a plethora of symptoms. Most patients give a history of blunt trauma or an increase in repetitive sporting activities, but any form of chronic or transient synovitis can cause the plica to lose its elasticity by becoming inflamed and thickened. Such changes can affect suprapatellar and medial para-patellar plicae, which may bowstring and impinge in the patello-femoral joint during flexion, subsequently leading to localised chondromalacia. As the clinical picture is not well defined, a high degree of suspicion is required. MRI might be of value in the diagnostic assessment. The clinical diagnosis, however, is one of exclusion, and other more common pathologies relating to antero-medial knee pain should be considered first. Arthroscopy remains the gold standard for treatment of pathological plicae, although intraplical injection and physiotherapy might be beneficial in patients with a short history of symptoms. Complete excision is recommended and provides satisfactory results especially if the plica represents the only intra-articular pathology.