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Anterior Knee Pain
Professional articles
Key Words Plica, knee, pain.
523
by Solomon Abrahams James H Kern
Anterior Knee Pain Plica syndrome, the forgotten pathology?
Summary The following article is a literature review of plica syndrome. It demonstrates that although it is not commonly diagnosed in clinical practice, its occurrence and relevance are important and should not be excluded from a knee examination. Further, if the fundamentals of plica syndrome can be understood, this may lead to a greater success in diagnosis and management. A synovial plica is a shelf-like membrane between the synovium of the patella and the tibiofemoral joint. Three plicae are found in the knee: suprapatellar, medial and inferior. A symptomatic plica causes pain, clicking, effusion, instability and locking of the patellofemoral joint. It is common in teenagers, more so in women than in men. A suprapatellar plica is found generally within the suprapatellar pouch and its occurrence ranges from 65% to 78%. Medial plicae are commonly found between the medial border of the patella and medial femoral condyle and are the most problematic. There are five medial plicae, all found in different anatomical positions. The inferior plica is found anterior to the intercondylar notch inserting into the infrapatellar fat pad. Mechanism of injury is varied, but principally repeated flexion-extension movements such as those seen in cycling, running and rowing sports can exacerbate the asymptomatic plicae. The pathophysiology constitutes repetitive microtrauma causing fibrosis and thickening of the synovium, inflammation and fluid production and increases articular pressure and loose bodies within the patellofemoral joint. This can mimic an internal derangement of the knee and can be mistaken for a torn anterior cruciate ligament on arthroscopy. Clinical examination may reveal some mal-tracking of the patella and in some cases the plicae may be palpable. Several tests are discussed in the text. Conservative treatment is advocated initially, including physiotherapy to help reduce inflammation. Arthroscopy and resection are also implicated in some cases. These are further discussed. The literature review of plica syndrome was initiated using a Medline search (1940-1999) using the key words ‘plicae’, ‘patellofemoral pain’ and ‘anterior knee pain’.
Introduction A synovial pleat or plica is a shelf-like membrane that is found between the synovium of the patella and the tibial femoral joint. It is thought to be the residual vestiges of embryonic divisions of the compartments within the knee (Muse et al, 1985). A plica is not always present within a normal knee but, if one is present, it may consist of not one but three separate plicae (Aprin et al, 1983). Plicae are not normally symptomatic but, if symptoms occur, they are not easily distinguishable from other conditions and derangements of the knee joint. This can lead to plicae being overlooked during traditional open knee surgery (Dupont, 1997). The first article linking clinical signs with synovial plicae syndrome was presented by Pipkin in 1950 and this link became accepted with the introduction of arthroscopy in the 1970s, resulting in greater interest and research (Harty 1978; Muntizinger et al, 1979; Dandy 1987; Patel, 1991) This paper aims to determine the present level of understanding of synovial plicae, specifically the anatomy, pathophysiology, diagnosis, and treatments available. Overview The plicae are considered normal anatomic structures within the knee (Kim and Choe, 1996). There are many models describing the plicae although most authors have adopted the one proposed by Hardaker et al (1980). This model describes three plicae generally referred to as the suprapatellar, mediopatellar and infrapatellar plica. Not all authors agree with this model and propose that between two and eight plicae can be present. One or more of the plicae can become symptomatic, causing pain, clicking, Physiotherapy October 2001/vol 87/no 10
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Suprapatellar plica
effusion and pseudolocking (Patel, 1986). Generally it is the mediopatellar plica that becomes symptomatic although occasionally problems arise from the suprapatellar plica. The infrapatellar plica, although large, rarely causes symptoms (Nisonson and Tindel, 1990; Kim and Choe, 1996; Subotinick, 1996). Embryology The embryonic development of plicae has been researched abundantly in the early twentieth century and the resulting theories vary between authors. Most studies concur that in the early stages of development of a human embryo, a mesenchymal tissue fills the space between the distal femoral and proximal tibia epiphysis (Patel, 1991). After approximately 10 to 12 weeks of embryonic development the tissue begins to separate. Some of the tissue coagulates to form the cruciate ligament and menisci while the remainder is reabsorbed to form one undivided cavity between the femoral compartment and the patella (Amatuzzi et al, 1990). Incomplete reabsorption of the mesenchymal tissue, ranging from 5% to 50%, results in the formation of a plica (Pipkin, 1971; Jackson et al, 1982; Muse et al, 1985).
Abrahams, S and Kern, J H (2000). ‘Anterior knee pain: Plica syndrome, the forgotten pathology?’ Physiotherapy, 87, 10, 523-528.
Suprapatellar Plica The suprapatellar plica, also referred to as the synovialis suprapatellaris, superior plica, supramedial plica and medial suprapatellar plica (Dupont, 1997), is a domed, crescent shaped septum that generally lies between the suprapatellar bursa and the tibiofemoral joint of the knee (fig 1). It is attached to the supromedial and lateral walls of the knee joint and arises from the under surface of the quadriceps tendon (Patel, 1986). Its direction is often oblique and in flexion it tends to rotate becoming parallel to the quadriceps muscle. In extension, the open packed position of the patellofemoral joint, the plica is free to move without becoming impinged on any surface of the knee such as the articular cartilage of the patella or trochlea (Jackson et al, 1982). The reported occurrence of the suprapatellar plica varies greatly between studies, ranging from 100% (Dupont, 1997) to 0% (Cascells and Morgan, 1984) of knees examined having some form of superior plica. Generally the occurrence
Physiotherapy October 2001/vol 87/no 10
Cruciate ligaments
Medial plica
Fig 1: Suprapatellar plica
of the suprapatellar plica is accepted to be between 65% and 78% (Pipkin, 1950; Older et al, 1986). Medial Plica The medial plica is referred to as the medial shelf, medial intra-articular band, medial patella plica and synovial shelf (Muse et al, 1985; Barber, 1987; Amatuzzi et al, 1990) and is used as a blanket term to describe several synovial structures. It is generally accepted that there are five synovial structures: the medial plica, plica alaris elongata, anteromedial fringe, superior-medial plica and transverse arcuate folds within the medial gutter (Dupont, 1997) although eight have been reported (Dandy, 1987). These features originate from either the superior synovial wall extending obliquely inferiorly to the synovial membrane covering the infrapatellar fatpad (Patel, 1986) or from under the surface of the quadriceps expansion to the medial femoral condyle (Muntizinger et al, 1979) (fig 2). The medial plica is considered the most problematic by many authors (Muse et al, 1985; Patel, 1986; Kim and Choe, 1996; Dupont, 1997) due to its close proximity to the medial border of the patella and medial femoral condyle where it can be ‘impinged’. The occurrence of medial plicae within subjects differs markedly between studies and ranges between 19% and 70% (Dupont, 1997).
Professional articles
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Medial plica
Cruciate ligament
Fig 2: Medial plica
Inferior Plica The inferior plica is also called the ligamentum mucosum, infrapatellar plica, infrapatellar fold and infrapatellar septum. It is located in the intercondylar area anterior to the anterior cruciate ligament and inserts distally into the fatpad (Dupont, 1997) (fig 3). Its crosssection can vary between subjects and is, in some cases, comparable in general size to the anterior cruciate ligament. This form of plica is rarely considered pathological or problematic (Kim and Choe, 1996; Muse et al, 1985) but can be
Medial plica
Cruciate ligament
Fig 3: Inferior plica
significant during arthroscopy (Muse et al, 1985; Krause et al, 1990; Kim and Choe, 1996). It is the consensus of opinion between authors that the infrapatellar plica is the most common plica found during arthroscopy occurring in 52% to 85% of subjects examined (Dupont, 1997).
Authors
Lateral Plica The lateral plica is rare with Tea0rse et al (1988) finding only 21 lateral plica in 3,000 arthroscopies (0.7%). Various studies do not acknowledge its existence, but it has been described as longitudinal, thin and located 1-2 cm lateral to the patella (Dupont, 1997).
James H Kern BSc PhD is a clinical researcher within the private sector.
Mechanism of Injury Plica injuries are usually caused by direct trauma, especially to a flexed knee, leading to haemorrhaging and often leading to effusion and synovitis (Patel, 1986), although other intrinsic factors can encourage the development of synovitis (Amatuzzi et al, 1990). Studies have reported high incidences of plica within athletes who repeatedly flex their knees during sports such as rowing, swimming, cycling and running (Dupont, 1997). It is proposed that each flexion/extension creates small microtraumas resulting in synovitis, effusion and pain. However, Dorchak et al (1991) reported 13 cases of plica syndrome in 31 patients with no previous history of trauma or overuse. Patients are normally young and have a history of acute injury such as blunt trauma (Veth et al, 1983).
J Solomon Abrahams BSc DipAPPhysSpor MCSP is a physiotherapy clinical specialist and lecturer at the University of Middlesex.
Address for Correspondence Mr S Abrahams, Kenton Bridge Physiotherapy, 155-175 Kenton Road, Kenton, Middlesex HA3 0YX. This article was received on April 6, 2000, and accepted on May 8, 2001.
Pathophysiology It has been proposed that an enlarged plica separates the knee joint into two cavities, a fluid reservoir and the cavity of the knee joint. Synovial fluid is able to flow between the two cavities with the plica acting as a valve mechanism sometimes impeding fluid flow. In this case, sudden alterations in intra-articular pressure can occur causing local inflammation, thickening and fibrosis of the joint lining resulting in pain (Amatuzzi et al, 1990). This pain can mimic the symptoms of an internal derangement of the knee such as menisci tears, lose bodies, infrapatellar fatpad adhesions, anterior cruciate ligament shortening and intra-articular haematoma Physiotherapy October 2001/vol 87/no 10
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(Muntizinger et al, 1979). The plica will also lose elasticity and eventually interfere with the normal glide pattern of the patellofemoral joint, causing damage to the articular cartilage on the patella and femoral condyle. Ultimately a cyst may form on the plica that can assume enormous proportions. It has also been suggested that debris within the knee, generated by trauma, can gather in the suprapatellar bursa and sometimes hide within the plica if the fold is large enough (Patel, 1986). After repeated flexion of the knee, debris can cause erosion of the articular cartilage due to compression of the joint, thereby causing chondromalacia. Quadriceps atrophy can occur in up to 45% of patients with a pathological plica (Hardaker et al, 1980). This concurs with the current view that atrophy is caused by chondromalacia and develops soon after the plica irritation (Amatuzzi et al, 1990). Of the patients examined with atrophy, 42% displayed signs of patellofemoral instability, although this link may be superficial. In the case of medial plica trauma, biomechanical factors may cause it to enlarge, resulting in impingement between the medial border of the trochlea’s medial facet and the medial facet of the patella. Impingement occurs during flexion of the knee between 40˚ and 80˚ when the gap between the patella and femoral joint is at its closest (Muse et al, 1985). Continued impingement of the plica with repeated flexion may cause chondromalacia, groove formation within the articular cartilage and a thickening of the plica (Aprin et al, 1983). This is associated with a clicking or loud snapping sound on flexion/extension of the knee (Patel, 1986). Occurrence of symptoms is rare with an inferior plica (Dupont, 1997) but when this occurs, the infrapatellar fatpad was often found to be hypertrophied. The clinical significance of this was not mentioned. Signs and Symptoms Snapping, pseudolocking, and clicking are indicative of a pathological plica. Patients can also present with localised swelling, reduced range of motion, marked instability of the patellofemoral joint and intermittent medial joint pain that is increased by flexion/extension Physiotherapy October 2001/vol 87/no 10
moments (Muse et al, 1985; Amatuzzi et al, 1990; Dupont, 1997). Local joint tenderness over the medial femoral condyle may also occur (Gardener and O’Rahilly, 1968; Veth et al, 1983; Muse et al, 1985; Barber, 1987) but this can be a symptom of meniscal lesions (Gardener and O’Rahilly, 1968). Clinical Examination Medial patella pain is common and has many different causes: maltracking of the patella, chondromalacia patella or a symptomatic medial plica (Dupont, 1997). Hence the clinical examination should always be an adjunct to patients’ history and their symptoms. The majority of the research on plicae has concentrated principally on the medial plica. On examination, a medial plica may occasionally be palpated one fingerbreadth away from the medial border of the patella (Patel, 1986). If pain is induced during the examination and a cord-like structure felt, this is indicative of a symptomatic medial plica. If a cord-like structure is felt but no pain is induced it indicates the presence of a nonsymptomatic medial plica and the symptomatic knee should be compared to the opposite knee (Muntizinger et al, 1979). Specific tests for a medial plica include the mediopatellar plica (fig 4) and plica shutter test. During the mediopatellar plica test the patient lies in supine and the examiner bends the affected leg to 30˚ flexion. The examiner then moves the Lateral border
Medial border
Direction of push
Patella
Fig 4: Mediopatellar plica test
Professional articles
patella medially and if pain is induced along the medial margin, this indicates the presence of a medial plica where it is pinched between the medial femoral condyle and the medial border of the patella (Magee, 1992). During the plica shutter test the patient sits on the end of the couch with both knees flexed at 90˚, the examiner then places one hand over the patella and the patient is asked to extend the knee. If the patella stutters or jumps between 45˚ and 60˚ it is indicative of a medial plica; however the test will not work if the joint is swollen (Magee, 1992). Other methods of examination that may indicate the presence of a medial plica include the medial subluxation test, McMurray’s test for menisci, Appley’s test for instability and Cabot’s test. It has also been suggested that there may be a positive apprehension test in girls with symptomatic medial plicae (Patel, 1986). If a suprapatellar plica is suspected the patient is asked to lie in supine while the examiner flexes the knee. The tibia is rotated medially while the patella is palpated medially and if a ‘pop’ is felt, this indicates the presence of a plica (Amatuzzi et al, 1990; Magee, 1992). The popping may be absent or disappear during the day because of synovitis and the production of a small effusion that buffers the sound (Amatuzzi et al, 1990). Management If plica syndrome is diagnosed as the pathology causing the pain, conservative treatment such as rest, application of ice, physiotherapy, ultrasound or diathermy may be of use initially to reduce inflammation. Patellar bracing where indicated, stretches and isometric quadriceps exercises to improve patella congruency can reduce irritation and are more cost-effective than arthroscopy (Pipkin, 1971; Amatuzzi et al, 1990; Dupont, 1997). It is estimated that the success rate
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using conservative treatment is approximately 20% (Hardaker et al, 1980; Aprin et al, 1983). Although this percentage is low these treatments can be very effective before operative procedures (Muse et al, 1985; Tindel and Nisonson, 1992). Generally if symptoms persist for longer than 12 weeks arthroscopy is considered (Patel, 1978; Hardaker et al, 1980; Jackson et al, 1982; Muse et al, 1985). For patients in severe pain, non-steroid anti-inflammatory drugs or a cortisone injection into the patellofemoral joint may be prescribed (Dupont, 1997) producing recovery in 71% of patients and reducing the symptoms in a further 19%. If arthroscopy is performed then a total resection of the plica, whether normal or pathological, is often per formed to prevent further problems arising (Muse et al, 1985), although not all authors agree with this procedure if a non-pathological plica is present (Patel, 1986). Conclusion The present understanding of plicae remains limited, with anatomy, pathophysiology and management being only recently investigated. Research has shown that the anatomy of a plica is far more complex than once thought and many anatomical variations of the plica have been reported. Unfortunately, there is still no reliable objective test to diagnose this pathology and diagnosis can be assessed only by using patient history, symptoms and clinical examination. Positive identification, at present, can be determined only through arthroscopy which is invasive, time-consuming and expensive. The only treatments available are arthroscopy and resection of the plica or physiotherapy, with a success rate of approximately 95% and 20% respectively. If the fundamentals of plica syndrome can be understood this may lead to greater success in diagnosis and management.
References Amatuzzi, M, Fazzi, A and Varella, M (1990). ‘Pathological synovial plica of the knee’, American Journal of Sports Medicine, 18, 5, 466-469. Aprin, H, Shapiro, J and Gerschwind, M (1983). ‘Arthrography (plica views)’ Clinical Orthopaedics and Related Research, 68, 1, 90-95.
Barber, F (1987). ‘Fenestrated medial patella plica’, Arthroscopy, 3, 253-257. Cascells, S and Morgan, C (1984). ‘Evaluation of the patellofemoral joint and the suprapatellar pouch’, Update in Arthroscopic Techniques, University Park Press, Baltimore, pages 25-34.
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Dandy, D (1987). Arthroscopic Surgery of the Knee, Churchill Livingstone, London, 2nd edn.
Nisonson, B and Tindel, N (1990). ‘The plica syndrome’, Seminar Orthopedics, 5, 160.
Dupont, J (1997). ‘Synovial plicae of the knee’, Arthroscopic Surgery, 16, 1, 86-122.
Older, J, Hanspal, R and Cardoso, T (1986). ‘The medial shelf’ in: Trickey, E L (ed) Surgery and Arthroscopy of the Knee, Springer Verlag, Berlin, pages 82-86.
Gardener, E and O’Rahilly, R (1968). ‘The early development of the knee joint in staged human embryos’, Journal of Anatomy, 102, 289-299. Hardaker, W, Whipple, T and Bassett, F (1980). ‘Diagnosis and treatment of plica syndrome of the knee’, Journal of Bone and Joint Surgery of America, 66, 221-226. Harty, M (1978). Arthroscopic Anatomy, American Academy of Orthopaedic Surgeons, Mosby, Illinois. Jackson, R, Marshall, D and Fujisawa, Y (1982). ‘The pathological medial shelf’, Orthopedic Clinics of North America, 13, 307-312. Kim, S and Choe, W (1996). ‘Pathological infrapatellar plica: Case report’, Journal of Arthroscopic and Related Research, 12, 2, 236-239. Krause, B, Williams, J and Catterall, A (1990). ‘A natural history of Osgood Schlatter disease’, Journal of Orthopaedic Paediatrics, 10, 65-68. Magee, D (1992). Orthopedic Physical Assessment, W B Saunders, London, 2nd edn. McDermott, L (1943). ‘Development of the human knee joint’, Archive Surgery, 46, 705-719. Muse, G, Grana, W and Hollingsworth, S (1985). ‘Arthroscopic treatment of medial shelf syndrome’, Journal of Arthroscopy, 1, 63-67. Muntizinger, U, Ruckstuhl, J, Scherrer, H and Gschwend, N (1979). ‘Internal derangement of the knee joint due to pathological synovial folds: The mediopatellar plica syndrome’, Clinical Orthopaedics and Related Research, 155, 59-64.
Patel, D (1978). ‘Arthroscopy of plica synovial folds and their significance’, American Journal of Sports Medicine, 6, 217. Patel, D (1986). ‘Plica: A cause of anterior knee pain’, Orthopedic Clinics of North America, 17, 2, 273-277. Patel, D (1991). ‘Synovial lesions: Plica’ in: McGinty, J B (ed) Operative Arthroscopy, Raven Press, New York, pages 361-377. Pipkin, G (1950). ‘Lesions of the suprapatellar plica’, Journal of Bone and Joint Surgery of America, 32, 363-369. Pipkin, G (1971). ‘Knee injuries: The role of the suprapatellar plica and suprapatellar bursa in simulating internal derangements’, Clinical Orthopedics, 74, 161-176. Subotnick, S and Sinsey, P (1986). ‘The plica syndrome: A cause of knee pain in the athlete’, Journal of American Podiatric Association, 76, 292. Tearse, D, Clancy, W and Gersoff, W (1988). ‘The symptomatic lateral plica of the knee’, Proceedings of the Seventh Annual Meeting of the Arthroscopy Association of North America, Washington DC. Tindel, N and Nisonson, B (1992). ‘The plica syndrome’, Orthopedic Clinics of North America, 23, 613. Veth, R, Den Heeten, G and Jansen, H (1983). ‘Repair of meniscus’, Clinical Orthopaedics, 175, 258.
Key Messages ■ A plica is a shelf-like membrane found between the patella and the tibiofemoral joint.
■ Plica syndrome can mimic mal-tracking and patellofemoral instability pathologies.
■ There are up to three plicae within the normal knee, mostly asymptomatic.
■ Plica testing should be part of any patellofemoral knee examination.
■ Symptomatic plicae can cause anterior knee pain, clicking, instability and locking.
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■ Physiotherapy rarely cures this pathology; surgery is normally advocated.
Key Words Plica, knee, pain.
523
by Solomon Abrahams James H Kern
Anterior Knee Pain Plica syndrome, the forgotten pathology?
Summary The following article is a literature review of plica syndrome. It demonstrates that although it is not commonly diagnosed in clinical practice, its occurrence and relevance are important and should not be excluded from a knee examination. Further, if the fundamentals of plica syndrome can be understood, this may lead to a greater success in diagnosis and management. A synovial plica is a shelf-like membrane between the synovium of the patella and the tibiofemoral joint. Three plicae are found in the knee: suprapatellar, medial and inferior. A symptomatic plica causes pain, clicking, effusion, instability and locking of the patellofemoral joint. It is common in teenagers, more so in women than in men. A suprapatellar plica is found generally within the suprapatellar pouch and its occurrence ranges from 65% to 78%. Medial plicae are commonly found between the medial border of the patella and medial femoral condyle and are the most problematic. There are five medial plicae, all found in different anatomical positions. The inferior plica is found anterior to the intercondylar notch inserting into the infrapatellar fat pad. Mechanism of injury is varied, but principally repeated flexion-extension movements such as those seen in cycling, running and rowing sports can exacerbate the asymptomatic plicae. The pathophysiology constitutes repetitive microtrauma causing fibrosis and thickening of the synovium, inflammation and fluid production and increases articular pressure and loose bodies within the patellofemoral joint. This can mimic an internal derangement of the knee and can be mistaken for a torn anterior cruciate ligament on arthroscopy. Clinical examination may reveal some mal-tracking of the patella and in some cases the plicae may be palpable. Several tests are discussed in the text. Conservative treatment is advocated initially, including physiotherapy to help reduce inflammation. Arthroscopy and resection are also implicated in some cases. These are further discussed. The literature review of plica syndrome was initiated using a Medline search (1940-1999) using the key words ‘plicae’, ‘patellofemoral pain’ and ‘anterior knee pain’.
Introduction A synovial pleat or plica is a shelf-like membrane that is found between the synovium of the patella and the tibial femoral joint. It is thought to be the residual vestiges of embryonic divisions of the compartments within the knee (Muse et al, 1985). A plica is not always present within a normal knee but, if one is present, it may consist of not one but three separate plicae (Aprin et al, 1983). Plicae are not normally symptomatic but, if symptoms occur, they are not easily distinguishable from other conditions and derangements of the knee joint. This can lead to plicae being overlooked during traditional open knee surgery (Dupont, 1997). The first article linking clinical signs with synovial plicae syndrome was presented by Pipkin in 1950 and this link became accepted with the introduction of arthroscopy in the 1970s, resulting in greater interest and research (Harty 1978; Muntizinger et al, 1979; Dandy 1987; Patel, 1991) This paper aims to determine the present level of understanding of synovial plicae, specifically the anatomy, pathophysiology, diagnosis, and treatments available. Overview The plicae are considered normal anatomic structures within the knee (Kim and Choe, 1996). There are many models describing the plicae although most authors have adopted the one proposed by Hardaker et al (1980). This model describes three plicae generally referred to as the suprapatellar, mediopatellar and infrapatellar plica. Not all authors agree with this model and propose that between two and eight plicae can be present. One or more of the plicae can become symptomatic, causing pain, clicking, Physiotherapy October 2001/vol 87/no 10
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Suprapatellar plica
effusion and pseudolocking (Patel, 1986). Generally it is the mediopatellar plica that becomes symptomatic although occasionally problems arise from the suprapatellar plica. The infrapatellar plica, although large, rarely causes symptoms (Nisonson and Tindel, 1990; Kim and Choe, 1996; Subotinick, 1996). Embryology The embryonic development of plicae has been researched abundantly in the early twentieth century and the resulting theories vary between authors. Most studies concur that in the early stages of development of a human embryo, a mesenchymal tissue fills the space between the distal femoral and proximal tibia epiphysis (Patel, 1991). After approximately 10 to 12 weeks of embryonic development the tissue begins to separate. Some of the tissue coagulates to form the cruciate ligament and menisci while the remainder is reabsorbed to form one undivided cavity between the femoral compartment and the patella (Amatuzzi et al, 1990). Incomplete reabsorption of the mesenchymal tissue, ranging from 5% to 50%, results in the formation of a plica (Pipkin, 1971; Jackson et al, 1982; Muse et al, 1985).
Abrahams, S and Kern, J H (2000). ‘Anterior knee pain: Plica syndrome, the forgotten pathology?’ Physiotherapy, 87, 10, 523-528.
Suprapatellar Plica The suprapatellar plica, also referred to as the synovialis suprapatellaris, superior plica, supramedial plica and medial suprapatellar plica (Dupont, 1997), is a domed, crescent shaped septum that generally lies between the suprapatellar bursa and the tibiofemoral joint of the knee (fig 1). It is attached to the supromedial and lateral walls of the knee joint and arises from the under surface of the quadriceps tendon (Patel, 1986). Its direction is often oblique and in flexion it tends to rotate becoming parallel to the quadriceps muscle. In extension, the open packed position of the patellofemoral joint, the plica is free to move without becoming impinged on any surface of the knee such as the articular cartilage of the patella or trochlea (Jackson et al, 1982). The reported occurrence of the suprapatellar plica varies greatly between studies, ranging from 100% (Dupont, 1997) to 0% (Cascells and Morgan, 1984) of knees examined having some form of superior plica. Generally the occurrence
Physiotherapy October 2001/vol 87/no 10
Cruciate ligaments
Medial plica
Fig 1: Suprapatellar plica
of the suprapatellar plica is accepted to be between 65% and 78% (Pipkin, 1950; Older et al, 1986). Medial Plica The medial plica is referred to as the medial shelf, medial intra-articular band, medial patella plica and synovial shelf (Muse et al, 1985; Barber, 1987; Amatuzzi et al, 1990) and is used as a blanket term to describe several synovial structures. It is generally accepted that there are five synovial structures: the medial plica, plica alaris elongata, anteromedial fringe, superior-medial plica and transverse arcuate folds within the medial gutter (Dupont, 1997) although eight have been reported (Dandy, 1987). These features originate from either the superior synovial wall extending obliquely inferiorly to the synovial membrane covering the infrapatellar fatpad (Patel, 1986) or from under the surface of the quadriceps expansion to the medial femoral condyle (Muntizinger et al, 1979) (fig 2). The medial plica is considered the most problematic by many authors (Muse et al, 1985; Patel, 1986; Kim and Choe, 1996; Dupont, 1997) due to its close proximity to the medial border of the patella and medial femoral condyle where it can be ‘impinged’. The occurrence of medial plicae within subjects differs markedly between studies and ranges between 19% and 70% (Dupont, 1997).
Professional articles
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Medial plica
Cruciate ligament
Fig 2: Medial plica
Inferior Plica The inferior plica is also called the ligamentum mucosum, infrapatellar plica, infrapatellar fold and infrapatellar septum. It is located in the intercondylar area anterior to the anterior cruciate ligament and inserts distally into the fatpad (Dupont, 1997) (fig 3). Its crosssection can vary between subjects and is, in some cases, comparable in general size to the anterior cruciate ligament. This form of plica is rarely considered pathological or problematic (Kim and Choe, 1996; Muse et al, 1985) but can be
Medial plica
Cruciate ligament
Fig 3: Inferior plica
significant during arthroscopy (Muse et al, 1985; Krause et al, 1990; Kim and Choe, 1996). It is the consensus of opinion between authors that the infrapatellar plica is the most common plica found during arthroscopy occurring in 52% to 85% of subjects examined (Dupont, 1997).
Authors
Lateral Plica The lateral plica is rare with Tea0rse et al (1988) finding only 21 lateral plica in 3,000 arthroscopies (0.7%). Various studies do not acknowledge its existence, but it has been described as longitudinal, thin and located 1-2 cm lateral to the patella (Dupont, 1997).
James H Kern BSc PhD is a clinical researcher within the private sector.
Mechanism of Injury Plica injuries are usually caused by direct trauma, especially to a flexed knee, leading to haemorrhaging and often leading to effusion and synovitis (Patel, 1986), although other intrinsic factors can encourage the development of synovitis (Amatuzzi et al, 1990). Studies have reported high incidences of plica within athletes who repeatedly flex their knees during sports such as rowing, swimming, cycling and running (Dupont, 1997). It is proposed that each flexion/extension creates small microtraumas resulting in synovitis, effusion and pain. However, Dorchak et al (1991) reported 13 cases of plica syndrome in 31 patients with no previous history of trauma or overuse. Patients are normally young and have a history of acute injury such as blunt trauma (Veth et al, 1983).
J Solomon Abrahams BSc DipAPPhysSpor MCSP is a physiotherapy clinical specialist and lecturer at the University of Middlesex.
Address for Correspondence Mr S Abrahams, Kenton Bridge Physiotherapy, 155-175 Kenton Road, Kenton, Middlesex HA3 0YX. This article was received on April 6, 2000, and accepted on May 8, 2001.
Pathophysiology It has been proposed that an enlarged plica separates the knee joint into two cavities, a fluid reservoir and the cavity of the knee joint. Synovial fluid is able to flow between the two cavities with the plica acting as a valve mechanism sometimes impeding fluid flow. In this case, sudden alterations in intra-articular pressure can occur causing local inflammation, thickening and fibrosis of the joint lining resulting in pain (Amatuzzi et al, 1990). This pain can mimic the symptoms of an internal derangement of the knee such as menisci tears, lose bodies, infrapatellar fatpad adhesions, anterior cruciate ligament shortening and intra-articular haematoma Physiotherapy October 2001/vol 87/no 10
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(Muntizinger et al, 1979). The plica will also lose elasticity and eventually interfere with the normal glide pattern of the patellofemoral joint, causing damage to the articular cartilage on the patella and femoral condyle. Ultimately a cyst may form on the plica that can assume enormous proportions. It has also been suggested that debris within the knee, generated by trauma, can gather in the suprapatellar bursa and sometimes hide within the plica if the fold is large enough (Patel, 1986). After repeated flexion of the knee, debris can cause erosion of the articular cartilage due to compression of the joint, thereby causing chondromalacia. Quadriceps atrophy can occur in up to 45% of patients with a pathological plica (Hardaker et al, 1980). This concurs with the current view that atrophy is caused by chondromalacia and develops soon after the plica irritation (Amatuzzi et al, 1990). Of the patients examined with atrophy, 42% displayed signs of patellofemoral instability, although this link may be superficial. In the case of medial plica trauma, biomechanical factors may cause it to enlarge, resulting in impingement between the medial border of the trochlea’s medial facet and the medial facet of the patella. Impingement occurs during flexion of the knee between 40˚ and 80˚ when the gap between the patella and femoral joint is at its closest (Muse et al, 1985). Continued impingement of the plica with repeated flexion may cause chondromalacia, groove formation within the articular cartilage and a thickening of the plica (Aprin et al, 1983). This is associated with a clicking or loud snapping sound on flexion/extension of the knee (Patel, 1986). Occurrence of symptoms is rare with an inferior plica (Dupont, 1997) but when this occurs, the infrapatellar fatpad was often found to be hypertrophied. The clinical significance of this was not mentioned. Signs and Symptoms Snapping, pseudolocking, and clicking are indicative of a pathological plica. Patients can also present with localised swelling, reduced range of motion, marked instability of the patellofemoral joint and intermittent medial joint pain that is increased by flexion/extension Physiotherapy October 2001/vol 87/no 10
moments (Muse et al, 1985; Amatuzzi et al, 1990; Dupont, 1997). Local joint tenderness over the medial femoral condyle may also occur (Gardener and O’Rahilly, 1968; Veth et al, 1983; Muse et al, 1985; Barber, 1987) but this can be a symptom of meniscal lesions (Gardener and O’Rahilly, 1968). Clinical Examination Medial patella pain is common and has many different causes: maltracking of the patella, chondromalacia patella or a symptomatic medial plica (Dupont, 1997). Hence the clinical examination should always be an adjunct to patients’ history and their symptoms. The majority of the research on plicae has concentrated principally on the medial plica. On examination, a medial plica may occasionally be palpated one fingerbreadth away from the medial border of the patella (Patel, 1986). If pain is induced during the examination and a cord-like structure felt, this is indicative of a symptomatic medial plica. If a cord-like structure is felt but no pain is induced it indicates the presence of a nonsymptomatic medial plica and the symptomatic knee should be compared to the opposite knee (Muntizinger et al, 1979). Specific tests for a medial plica include the mediopatellar plica (fig 4) and plica shutter test. During the mediopatellar plica test the patient lies in supine and the examiner bends the affected leg to 30˚ flexion. The examiner then moves the Lateral border
Medial border
Direction of push
Patella
Fig 4: Mediopatellar plica test
Professional articles
patella medially and if pain is induced along the medial margin, this indicates the presence of a medial plica where it is pinched between the medial femoral condyle and the medial border of the patella (Magee, 1992). During the plica shutter test the patient sits on the end of the couch with both knees flexed at 90˚, the examiner then places one hand over the patella and the patient is asked to extend the knee. If the patella stutters or jumps between 45˚ and 60˚ it is indicative of a medial plica; however the test will not work if the joint is swollen (Magee, 1992). Other methods of examination that may indicate the presence of a medial plica include the medial subluxation test, McMurray’s test for menisci, Appley’s test for instability and Cabot’s test. It has also been suggested that there may be a positive apprehension test in girls with symptomatic medial plicae (Patel, 1986). If a suprapatellar plica is suspected the patient is asked to lie in supine while the examiner flexes the knee. The tibia is rotated medially while the patella is palpated medially and if a ‘pop’ is felt, this indicates the presence of a plica (Amatuzzi et al, 1990; Magee, 1992). The popping may be absent or disappear during the day because of synovitis and the production of a small effusion that buffers the sound (Amatuzzi et al, 1990). Management If plica syndrome is diagnosed as the pathology causing the pain, conservative treatment such as rest, application of ice, physiotherapy, ultrasound or diathermy may be of use initially to reduce inflammation. Patellar bracing where indicated, stretches and isometric quadriceps exercises to improve patella congruency can reduce irritation and are more cost-effective than arthroscopy (Pipkin, 1971; Amatuzzi et al, 1990; Dupont, 1997). It is estimated that the success rate
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using conservative treatment is approximately 20% (Hardaker et al, 1980; Aprin et al, 1983). Although this percentage is low these treatments can be very effective before operative procedures (Muse et al, 1985; Tindel and Nisonson, 1992). Generally if symptoms persist for longer than 12 weeks arthroscopy is considered (Patel, 1978; Hardaker et al, 1980; Jackson et al, 1982; Muse et al, 1985). For patients in severe pain, non-steroid anti-inflammatory drugs or a cortisone injection into the patellofemoral joint may be prescribed (Dupont, 1997) producing recovery in 71% of patients and reducing the symptoms in a further 19%. If arthroscopy is performed then a total resection of the plica, whether normal or pathological, is often per formed to prevent further problems arising (Muse et al, 1985), although not all authors agree with this procedure if a non-pathological plica is present (Patel, 1986). Conclusion The present understanding of plicae remains limited, with anatomy, pathophysiology and management being only recently investigated. Research has shown that the anatomy of a plica is far more complex than once thought and many anatomical variations of the plica have been reported. Unfortunately, there is still no reliable objective test to diagnose this pathology and diagnosis can be assessed only by using patient history, symptoms and clinical examination. Positive identification, at present, can be determined only through arthroscopy which is invasive, time-consuming and expensive. The only treatments available are arthroscopy and resection of the plica or physiotherapy, with a success rate of approximately 95% and 20% respectively. If the fundamentals of plica syndrome can be understood this may lead to greater success in diagnosis and management.
References Amatuzzi, M, Fazzi, A and Varella, M (1990). ‘Pathological synovial plica of the knee’, American Journal of Sports Medicine, 18, 5, 466-469. Aprin, H, Shapiro, J and Gerschwind, M (1983). ‘Arthrography (plica views)’ Clinical Orthopaedics and Related Research, 68, 1, 90-95.
Barber, F (1987). ‘Fenestrated medial patella plica’, Arthroscopy, 3, 253-257. Cascells, S and Morgan, C (1984). ‘Evaluation of the patellofemoral joint and the suprapatellar pouch’, Update in Arthroscopic Techniques, University Park Press, Baltimore, pages 25-34.
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Dandy, D (1987). Arthroscopic Surgery of the Knee, Churchill Livingstone, London, 2nd edn.
Nisonson, B and Tindel, N (1990). ‘The plica syndrome’, Seminar Orthopedics, 5, 160.
Dupont, J (1997). ‘Synovial plicae of the knee’, Arthroscopic Surgery, 16, 1, 86-122.
Older, J, Hanspal, R and Cardoso, T (1986). ‘The medial shelf’ in: Trickey, E L (ed) Surgery and Arthroscopy of the Knee, Springer Verlag, Berlin, pages 82-86.
Gardener, E and O’Rahilly, R (1968). ‘The early development of the knee joint in staged human embryos’, Journal of Anatomy, 102, 289-299. Hardaker, W, Whipple, T and Bassett, F (1980). ‘Diagnosis and treatment of plica syndrome of the knee’, Journal of Bone and Joint Surgery of America, 66, 221-226. Harty, M (1978). Arthroscopic Anatomy, American Academy of Orthopaedic Surgeons, Mosby, Illinois. Jackson, R, Marshall, D and Fujisawa, Y (1982). ‘The pathological medial shelf’, Orthopedic Clinics of North America, 13, 307-312. Kim, S and Choe, W (1996). ‘Pathological infrapatellar plica: Case report’, Journal of Arthroscopic and Related Research, 12, 2, 236-239. Krause, B, Williams, J and Catterall, A (1990). ‘A natural history of Osgood Schlatter disease’, Journal of Orthopaedic Paediatrics, 10, 65-68. Magee, D (1992). Orthopedic Physical Assessment, W B Saunders, London, 2nd edn. McDermott, L (1943). ‘Development of the human knee joint’, Archive Surgery, 46, 705-719. Muse, G, Grana, W and Hollingsworth, S (1985). ‘Arthroscopic treatment of medial shelf syndrome’, Journal of Arthroscopy, 1, 63-67. Muntizinger, U, Ruckstuhl, J, Scherrer, H and Gschwend, N (1979). ‘Internal derangement of the knee joint due to pathological synovial folds: The mediopatellar plica syndrome’, Clinical Orthopaedics and Related Research, 155, 59-64.
Patel, D (1978). ‘Arthroscopy of plica synovial folds and their significance’, American Journal of Sports Medicine, 6, 217. Patel, D (1986). ‘Plica: A cause of anterior knee pain’, Orthopedic Clinics of North America, 17, 2, 273-277. Patel, D (1991). ‘Synovial lesions: Plica’ in: McGinty, J B (ed) Operative Arthroscopy, Raven Press, New York, pages 361-377. Pipkin, G (1950). ‘Lesions of the suprapatellar plica’, Journal of Bone and Joint Surgery of America, 32, 363-369. Pipkin, G (1971). ‘Knee injuries: The role of the suprapatellar plica and suprapatellar bursa in simulating internal derangements’, Clinical Orthopedics, 74, 161-176. Subotnick, S and Sinsey, P (1986). ‘The plica syndrome: A cause of knee pain in the athlete’, Journal of American Podiatric Association, 76, 292. Tearse, D, Clancy, W and Gersoff, W (1988). ‘The symptomatic lateral plica of the knee’, Proceedings of the Seventh Annual Meeting of the Arthroscopy Association of North America, Washington DC. Tindel, N and Nisonson, B (1992). ‘The plica syndrome’, Orthopedic Clinics of North America, 23, 613. Veth, R, Den Heeten, G and Jansen, H (1983). ‘Repair of meniscus’, Clinical Orthopaedics, 175, 258.
Key Messages ■ A plica is a shelf-like membrane found between the patella and the tibiofemoral joint.
■ Plica syndrome can mimic mal-tracking and patellofemoral instability pathologies.
■ There are up to three plicae within the normal knee, mostly asymptomatic.
■ Plica testing should be part of any patellofemoral knee examination.
■ Symptomatic plicae can cause anterior knee pain, clicking, instability and locking.
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■ Physiotherapy rarely cures this pathology; surgery is normally advocated.