Plica: Pathologic or Not? J. Whit Ewing, MD Abstract A fold that occurs within a joint is referred to as a plica synovialis. Three such pli- in which the only finding to explain cae are seen with regularity within the human knee joint. These folds are normal the symptoms is the presence of a structures that represent remnants of mesenchymal tissue and/or septa formed thickened, hypertrophic plica. during embryonic development of the knee joint, and can be seen during arthro- Chronic anteromedial knee pain and scopic inspection of the knee joint. Controversy exists within the orthopaedic com- a sense of tightness in the subpatellar munity as to whether a plica can develop pathologic changes sufficient to cause region on squatting are the common disabling knee symptoms. The author defines the clinical syndrome, describes the complaints expressed by patients arthroscopic appearance of pathologic plica, and outlines nonsurgical and surgi- found to have a pathologic plica. The cal methods of management of this uncommon condition. ligamentum mucosum is not a J Am Acad Orthop Surg 1993;1:117-121 source of these types of symptoms. Additional symptoms are snapping sensations, buckling, knee pain on A plica synovialis is a membranous commonly referred to as a medial shelf sitting, and pain with repetitive fold or ridge found in the synovial or medial plica. This shelflike fold of activity.4 Recurrent effusions and lining of a joint. Three such folds are synovial membrane extends from the locking of the knee joint are not typi- found with regularity in the human infrapatellar fat pad to the medial wall cal in patients with this syndrome. knee. In the normal state, these folds of the knee, running in the coronal The usual differential diagnosis of are quite filmy, thin, and vascular- plane. The rarely seen plica synovialis patients with anterior knee pain ized, and have no known function. lateropatellaris, or lateral plica, is the includes jumper’s knee, torn menis- The most common plica, the plica same type of structure as the medial cus, patellar malalignment with or synovialis patellaris, usually referred plica. It extends from the fat pad later- without pathologic chondromalacia to as the ligamentum mucosum, is ally to end in the synovium of the lat- of the patella, bipartite patella, and located in the intercondylar notch, eral wall of the knee.2 The medial plica degenerative joint disease. It may be extending from below the level of the may appear to be contiguous with the difficult to distinguish plica syn- articular surface of the femur to the suprapatellar plica. drome from other pathologic condi- tibial plateau. It covers the anterior The suprapatellar plica and the lig- tions that produce similar symptoms. cruciate ligament and frequently amentum mucosum are thought to be However, the cause of the symptoms blocks its visualization during diag- remnants of septa dividing the supra- can often be determined by a careful nostic arthroscopy. patellar bursa and patellofemoral cav- physical examination. The second most frequently found itation and the medial and lateral plica is the plica synovialis supra- femorotibial cavitations, respectively. patellaris, commonly called the The medial and lateral plicae most History and Physical suprapatellar plica. It is located in the likely represent remnants of mes- Examination suprapatellar space, extending from enchymal tissue.3 The significance of the medial wall of the knee toward these folds of synovial tissue resides Approximately 50% of patients the lateral wall, and sometimes cre- in whether they can be the source of with plica syndrome present with a ates a complete septum between the pain and impairment of knee joint suprapatellar bursa and the knee function. Dr. Ewing is Professor of Orthopaedic Surgery, joint proper. It may be fenestrated in Northeastern Ohio Universities College of Medi- its central portion by an oval open- cine, Rootstown. ing, or porta. Wide variations in its Plica Syndrome Reprint requests: Dr. Ewing, Crystal Clinic, 1 shape and width are seen. 3975 Embassy Parkway, No. 102, Akron, OH The third most frequently seen plica Plica syndrome is defined as a 44333. is the plica synovialis mediopatellaris, painful impairment of knee function Vol 1, No 2, Nov/Dec 1993 117 Plica history of blunt trauma to the ante- A common source of anterior knee ate to institute a course of nonsurgical rior aspect of the knee. They will on pain, particularly in the active treatment.6 This treatment includes many occasions have a latent period younger age group, is infrapatellar rest from all strenuous physical activ- free of symptoms after the healing tendinitis, or jumper’s knee. Jumper’s ities, a course of nonsteroidal anti- of the initial injury, only to have the knee can be ruled out by careful inflammatory medication, moist heat delayed onset of anterior knee pain examination of the infrapatellar ten- applications, and hamstring stretch- some weeks or months later. Most don prior to an arthroscopic exami- ing. Resistive strengthening exercises of the remaining patients with this nation. This is done by depressing the should be avoided because they will syndrome have a history of the superior pole of the patella in the aggravate the symptoms, particu- development of pain following a relaxed fully extended knee, to ele- larly in the early phases of treatment. prolonged period of a strenuous vate the inferior pole of the patella. If there is relief of symptoms, the repetitive physical activity, such as The examiner then palpates the inser- patient can gradually be brought running, weight lifting, or step aer- tion of the infrapatellar tendon with back to his or her former activity level obics. Only a few patients will pre- the index finger by directing pressure with the usual counsel regarding sent without a history of trauma or superiorly, along the long axis of the alteration of level of participation in repetitive physical activity. leg. Extreme tenderness can be order to prevent a recurrence. Patients with plica syndrome elicited in the patient suffering from Intraplical injection of local cortico- usually present with tenderness in tendinitis. By establishing the diag- steroids has been advocated by some the medial parapatellar region. nosis of jumper’s knee in this fashion, as a treatment alternative,7 but I have Provocative tests to elicit this ten- many arthroscopic plica excisions no experience with this method of derness have been described by can be avoided. management. Failure to respond to Koshino and Okamoto5 and are Continued postoperative com- nonsurgical management leaves helpful in assessing patients with plaints of knee pain, aggravated by arthroscopic excision of the patho- anterior knee pain. The first test is attempts to strengthen the quadri- logic plica as the treatment of choice. done by palpating the medial bor- ceps mechanisms by resistive exer- der of the patella while producing cises, suggest infrapatellar tendinitis medial patellar displacement with either as a primary or an associated Arthroscopic Findings one hand and simultaneously pro- cause of anterior knee pain. A proper ducing knee valgus and internal or preoperative diagnosis can prevent Arthroscopically, the pathologic external rotation of the lower leg significant postoperative anxieties. medial plica appears as a thickened, with the other hand. The second avascular, wide (greater than 12 provocative test is referred to as the Diagnostic Tests mm), membranous band of tissue holding test. The patient is asked to (Fig. 1). It is best seen with the hold the knee in full extension while Routine radiographs of the affected arthroscope placed in the supra- the examiner attempts to flex it knee with plica syndrome are normal. patellar lateral portal.5,8 When pal- against the patient’s resistance. The Double-contrast arthrograms may pated with a blunt probe, the examiner again pushes the patella show the presence of a suprapatellar pathologic medial plica has the feel medially while palpating its medial plica, but cannot aid in determining of a taut bowstring. The medial plica border. Pain produced with or with- whether the plica is producing symp- may be seen to impinge between the out a click is considered a positive toms. Magnetic resonance imaging medial facet of the patella and the test in either case. has not been helpful to date in estab- medial surface of the trochlea when Additional findings include a lishing the diagnosis of plica syn- the knee is slowly flexed. The plica painful, palpable medial parapatellar drome. Routine laboratory tests, does not have to impinge between cord that can be rolled and popped including the standard chemistry the patella and the trochlea to be beneath the examining finger. Ten- panels ordered for establishing a considered pathologic. The charac- derness immediately over the joint diagnosis of inflammatory joint dis- teristic thickened, bowstring appear- line is the exception rather than the ease, are normal. ance of the plica is indicative of its rule. The knee should not exhibit any pathologic nature. signs of ligamentous instability or The pathologic suprapatellar patellar malalignment. The finding of Nonsurgical Treatment plica is usually somewhat thickened, a knee effusion is unusual; when pre- but never quite assumes the menis- sent, causes other than the plica syn- If a tentative diagnosis of plica syn- coid appearance of the abnormal drome should be considered. drome has been made, it is appropri- medial plica, which acts like a bow- 118 Journal of the American Academy of Orthopaedic Surgeons J. Whit Ewing, MD A B C Fig. 1 Pathologic medial plica. A, The arthroscope was placed in the superolateral portal, and a 70-degree fore-oblique lens was used for this image obtained with the knee in full extension. The patella is seen above the plica, which exhibits a dense, meniscoid appearance. B, The knee is flexed to 40 degrees.