Curr Rev Musculoskelet Med (2008) 1:53–60 DOI 10.1007/s12178-007-9006-z Medial plica irritation: diagnosis and treatment Chad J. Grifﬁth Æ Robert F. LaPrade Published online: 27 November 2007 Humana Press 2007 Abstract Medial plica irritation of the knee is a very common source of anterior knee pain. Patients can com- plain of pain over the anteromedial aspect of their knees and describe episodes of crepitation, catching, and pseudo- locking events with activities. Patients commonly have pain on physical examination upon rolling the plica fold of tissue over the anteromedial aspect of their knees and often have tight hamstrings. The majority of the patients will respond well to a non-operative treatment program con- sisting of quadriceps strengthening along with concurrent hamstring stretching. In cases which do not respond ini- tially to an exercise program, an intraarticular steroid injection may be indicated. In those few patients who do not respond to a non-operative treatment program, an arthroscopic resection of their medial plica may be indi- cated, especially in those cases where a shelf-like plica has been found to be causing damage to the articular cartilage of the medial femoral condyle. Keywords Plica irritation Anatomy The medial plica of the knee is a thin, well-vascularized intraarticular fold of the joint lining, or synovial tissue, over the medial aspect of the knee (Fig. 1). It is present in everyone, but is more prominent in some people. It has been noted to be present as a shelf of tissue over the medial C. J. Grifﬁth R. F. LaPrade (&) Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue, R200, Minneapolis, MN 55454, USA e-mail: lapra001@umn.edu aspect of the knee at the time of arthroscopic surgery in up to 95% of patients [6]. Proximally, it is attached to the genu articularis muscle, while distally it courses over the far medial aspect of the medial femoral condyle to attach to the distomedial aspect of the intraarticular synovial lining of the knee. At this location, it basically blends into the medial patellotibial ligament on the medial aspect of the retropatellar fat pad [9]. The medial plica is composed of relatively elastic tissues which asymptomatically conform to the changes in shape and lengths of the plica folds as the knee ﬂexes and extends [7]. In some patients, particularly those who may have had injuries or multiple surgeries over the medial aspect of the knee, the medial synovial plica may become very thick and ﬁbrotic and may catch over the medial aspect of the medial femoral condyle [7, 10]. In all patients, the medial synovial plica will glide over the anteromedial aspect of the medial femoral condyle with ﬂexion and extension of the knee. In most patients, this gliding motion of the plica will occur without any symp- toms, because of the high viscosity of the native synovial ﬂuid of the knee. However, in patients with effusions, which decreases the viscosity of their synovial ﬂuid, patients may either have crepitation or a catching of their medial synovial plica with ﬂexion and extension of the knee. This crepitation or catching can occur with patients while going up or down stairs, squatting and bending, and other types of activities. Since the medial synovial plica does have an attachment to the genu articularis muscle, and also an indirect attachment to the quadriceps musculature due to its attachment to the joint lining, it is dynamically controlled by the quadriceps muscles [3]. Thus, medial plica irritation is more common in patients who have poor quadriceps tone or other problems with joint muscle balance around the knee.