There are several studies reporting the incidence of suprapatellar, medial and lateral plicae, but there is very limited information regarding the incidence of the infrapatellar plica. The purpose of our study was to record the incidence of the infrapatelar plicae in the elderly Welsh population suffering of knee osteoarthritis. A prospective study was performed and 90 knees with severe osteoarthritis of the knee joint (Kellgren-Lawrence type III and IV) were investigated during total knee arthroplasty surgery.  Documentation was performed at every total knee replacement surgery for the length of the study. Knee replacement was performed by one senior surgeon. Infrapatellar plica was investigated by a medial parapatellar approach and was classified into five types according to Kim’s classification. The overall incidence of the infrapatellar plicae was 37.7%. The most common type of plicae was the separate type (23.3 %). There was no significant difference found between male and female patients. The fenestra type was the least common (2.22%). The incidence of infrapatellar plicae in the elderly Welsh population suffering of knee osteoarthritis was significantly lower when compared to a study that recorded the incidence of infrapatellar plica in young patients. Possibly, the degenerative changes of the knee joint can cause the reabsorption of the infrapatellar plica decreasing by this way its incidence in the elderly population.Key words: infrapatellar plicae, incidence, knee osteoarthritis, elderl

Apostolopoulos, A. P.

Manta, A.

McConnell, B.

Zafiropoulos, G.

English

Via Medica Journals

Folia Morphol. Vol. 71, No. 3, pp. 194–197Copyright © 2012 Via MedicaISSN 0015–5659www.fm.viamedica.plO R I G I N A L   A R T I C L E194Address for correspondence: A. Apostolopoulos, MsC, PhD, Prince Charles Hospital, Orthopaedic Department, Merthyr Tydfil, CF47 9DT,United Kingdom, e-mail: aalexgr2000@yahoo.comThe incidence of infrapatellar plicaein the elderly Welsh populationA.P. Apostolopoulos1, B. McConnell1, A. Manta1, G. Zafiropoulos1, 21Orthopaedic Department, Cwn Taf Health, Prince Charles Hospital, United Kingdom2University of Glamorgan, United Kingdom[Received 17 April 2012; Accepted 21 May 2012]There are several studies reporting the incidence of suprapatellar, medial, andlateral plicae, but there is very limited information regarding the incidence ofthe infrapatellar plica. The purpose of our study was to record the incidence ofinfrapatellar plicae in the elderly Welsh population suffering from knee os-teoarthritis. A prospective study was performed and 90 knees with severe os-teoarthritis of the knee joint (Kellgren-Lawrence type III and IV) were investi-gated during total knee arthroplasty surgery. Documentation was performedat every total knee replacement surgery for the length of the study. Knee re-placement was performed by one senior surgeon. Infrapatellar plica was inves-tigated by a medial parapatellar approach and was classified into five typesaccording to Kim’s classification. The overall incidence of infrapatellar plicaewas 37.7%. The most common type of plicae was the separate type (23.3%).There was no significant difference found between male and female patients.The fenestra type was the least common (2.22%). The incidence of infrapatel-lar plicae in the elderly Welsh population suffering from knee osteoarthritiswas significantly lower when compared to a study that recorded the incidenceof infrapatellar plica in young patients. Possibly, the degenerative changes ofthe knee joint can cause the resorption of the infrapatellar plica, thus decreasingits incidence in the elderly population. (Folia Morphol 2012; 71, 3: 194–197)Key words: infrapatellar plicae, incidence, knee osteoarthritis, elderlyINTRODUCTIONThe plicae around the knee joint are the embryo-logical remnants of the synovial membranes thatseparate the knee into three compartments duringembryologic development. A medial, lateral, andsuprapatellar compartment exists during the deve-lopment of the knee joint which occurs between the7th and 10th weeks of gestation. A single cavity formsafter the 16th week of gestation, due to the resorp-tion of the synovial membrane. Failure of resorp-tion of the synovial membrane can lead to the for-mation of the plicae. An infrapatellar plica is formedwhen there is incomplete regression of the mesen-chymal tissue between the medial and lateral com-partments of the knee [8].In our daily clinical practice we do not meet pa-tients with symptomatic infrapatellar plicae. Duringour previous surgical experience, infrapatellar plicawas not a common finding during total knee arthro-plasty and knee arthroscopy procedures. We there-fore hypothesised that the incidence of infrapatellarplicae is very low in the wide population. However,by the time we started to practice medicine in Wales,an infrapatellar plica was a common finding duringtotal knee arthroplasty procedures. We therefore de-cided to perform a prospective study and examine195A.P. Apostolopoulos et al., The incidence of infrapatellar plicae in the elderly Welsh populationthe incidence of infrapatellar plicae in the elderlyWelsh population.MATERIAL AND METHODSBetween 2009 and 2010 we performed a pro-spective study in 90 patients who were operatedfor total knee arthroplasties. Ninety patients(53 women, 37 men) were included in our study and90 total knee arthroplasties were performed. The meanage was 73.7 years (range 68–81 years). All patientssuffered from progressive osteoarthritis of the kneejoint (Kellgren Lawrence type III and IV) [9]. Thosewith previous knee surgeries, patella fractures, orintra-articular knee fractures were excluded from thestudy as they could alter the anatomy of the kneejoint. Patients not from the Welsh population werenot included in the study. Demographic data andintraoperative findings were documented. Documen-tation was performed at every total knee replace-ment surgery for the length of the study.Knee replacement was performed by one se-nior surgeon who specialised in knee surgery. Theinfrapatellar fat pad was not excised in any of thecases. Infrapatellar plicae were investigated bya medial parapatellar approach and were classifiedinto five types according to Kim’s classification[12]. Type A: vertical septum type, when the plicawas in continuation with the anterior surface ofthe anterior cruciate ligament (ACL); type B: sepa-rate type, when the plica was completely separat-ed by the ACL; type C: split type, when the plicawas completely separated by the ACL and therewas a longitudinal split; type D: fenestra type,when the plica was the vertical septum type witha fenestra; and type E: absent type.RESULTSInfrapatellar plicae were found in 36 knees, andthe overall incidence was 37.7%. There was no sig-nificant difference found between male and femalepatients or between right and left knees (Table 1).The plica was absent in 63.7% of the knees reviewed.The separate type (type B according to Kim’s classi-fication) was the most common as the plica was inmost cases completely separated by the ACL but nosplit was present (23.3%). The fenestra type was theleast common (2.22%).The plicae were found to be thickened and scle-rotic in 6 cases, possibly as a result of past traumathat caused the fibrotic changes.DISCUSSIONThe plicae were first described by Fullerton [7] andMayeda [15] in anatomic dissections that they per-formed in the first decade of the 20th century. Theirarthroscopic appearance was first described in 1939by Lino [14] in cadaveric studies that he performed.Four types of plicae have been described accord-ing to their anatomic morphology: medial, lateral,suprapatellar, and infrapatellar. The suprapatellarplica is the most common and lies between the su-prapatellar pouch and the knee. An incidence of70 to 91% has been reported in various arthroscop-ic studies [4, 10, 19]. It can have various shapes andDandy [4] made an arthroscopic classification bydescribing ten different variations.The medial plica is also known as the plica syn-ovialis mediopatelaris. It originates on the medialwall of the knee joint and inserts into the synovi-um surrounding the infrapatellar fat pad. Four dif-ferent types of medial plicae have been describedby Sakakibara et al. [21]. There are various stud-ies in the literature reporting the incidence ofmedial plica. Sakakibara reported an incidence ofless than 55%. In arthroscopic studies, Dandy [4]reported an incidence of 92% and Kim and Choe[10] an incidence of 72%. At the time of writing,the most recent study was performed by Nakaya-Table 1. Distribution of plicae type according to genderPlicae type Male Female TotalVertical septum 2 (5.40%) 2 (3.17%) 4 (4.44%)Separate type 8 (21.62%) 13 (20.63%) 21 (23.3%)Split type 2 (5.40%) 5 (7.93%) 7 (7.77%)Fenestra type 1 (2.70%) 1 (1.56%) 2 (2.22%)Absent type 24 (64.86%) 42 (66.66%) 66 (63.7 %)Total 37 63 90196Folia Morphol., 2012, Vol. 71, No. 3An intact ligamentum mucosum may be mistak-en for an intact anterior cruciate ligament dur-ing arthroscopy, until excised. It has also beenreported that the vertical septum type may beaccompanied by a discoid meniscus [20]. A re-cent retrospective study reported twelve cases ofanterior knee pain, not responding to non-opera-tive treatment, which underwent isolated infra-patellar plica resection without any other notedknee pathology. After one year of follow up theresults were, according to the authors, excellentin six cases and good in five cases [1].Ozcan et al. [18] reviewed 133 abnormal infrapa-tellar plicae under arthroscopy and evaluated the riskof chondral damage in the knee joint. The abnormalinfrapatellar plica originates from the superior aspectof the intercondylar notch and enters the superior as-pect of Hoffa’s fat pad. An abnormal plica becomesvertical during the extension of the knee and can causechondral lesions on the superior aspect of the inter-condylar notch and on the patellofemoral sulcus. Ac-cording to this study, the severity of the chondral le-sions was not associated with the shape or width ofthe plica. The anatomic location of the plica was im-portant in the formation of chondral lesions.There are very few studies in the literature review-ing the incidence of infrapatellar plicae. Kim et al. [11]examined 200 knees arthroscopically and the incidenceof the infrapatellar plica was 85.5%. The separate typewas the most common (65%) and the fenestra typewas the least common (1%). According to Kim et al.[11], the incidence of infrapatellar plicae decreases asthe age increases, probably due to absorption of theplicae, which occurs due to chronic injuries and de-generative changes. In Kim’s study, knees with degen-erative joint disease were excluded. The mean age ofpatients that were reviewed was 39.9 years. In ourstudy the overall incidence of the infrapatellar plicaewas 37.7% and was significantly lower than Kim’s pub-lished series. This difference could be explained by thefact that the mean age of our patients was 73.7 yearsand all our patients suffered from severe (KellgrenLawrence Grade III and IV) knee osteoarthritis. We cantherefore agree with Kim’s hypotheses that age anddegeneration can possibly cause the reabsorption ofthe infrapatellar plica and the incidence can be expect-ed to be lower in the elderly. Ozcan et al. [18] reviewed627 patients under arthroscopy. The mean age of thepatients was 43 years (range 16 to 84 years). Out ofthese patients 242 infrapatellar plicae were recordedand the incidence was 38.5%. In Ozcan’s study, thereis great age variability in the population reviewed.ma et al. [16]. In their study, they investigatedthe incidence of medial plica during arthroscopicsurgery in 3,889 knees in the Japanese popula-tion. An anterolateral portal approach was usedand a Sakakibara classification was performed.Medial plicae were detected in 3,107 knee jointsand the overall incidence was 79.9% [16].The infrapatellar plica, or ligamentum mucosum,originates from the intercondylar notch and insertsinto the synovium around the infrapatellar fat pador the inferior pole of the patella. Posteriorly the pli-ca may be entirely separated from the anterior cru-ciate ligament or be either partially or completelyattached to it. An arthroscopic classification has beendescribed by Kim et al. [12]. According to Kim’s clas-sification, an infrapatellar plica may be one of thefollowing types: absent, separated, split, verticalseptum, or fenestra.A normal plica is usually elastic and soft in struc-ture, and it is usually asymptomatic. Trauma of theknee joint and several inflammatory conditions cancause irritation and fibrotic changes of the plicae. Theplica can progressively lose its elastic properties andbecome thickened. This can lead to snapping of theplica over the femoral condyle causing synovitis,chondral damage, and pain.The most common type of symptomatic plica isthe medial plica. Cases of symptomatic suprapatel-lar plica have also been reported. The incidence ofthe lateral plica is very low and there are only fourreports of lateral plica syndrome in the literature [6].The infrapatellar plica was also considered tobe asymptomatic. However, in 1996 Kim et al.[12] reported two cases of flexion contracture ofthe knee that were arthroscopically found to bedue to impingement of a pathologic infrapatel-lar plicae in the intercondylar notch and the tro-chlea. In 2002 Kim et al. [11] reported anothercase of a pathologic symptomatic infrapatellarplica. During arthroscopy a fibrotic and scleroticfenestra pattern plica was described. The plicawas impinged at the intercondylar notch and tro-chlea blocking the extension of the knee joint.Grade 2 softening of the medial femoral condylewas also found [11]. In 2006, Demirag et al. [5]reported a series of 14 patients who had anteri-or knee pain and had no other pathology apartfrom a thickened infrapatellar plica that was ar-throscopically excised. The presence of an infra-patellar plica may also cause problems duringaspiration, arthroscopic visualisation of the an-terior cruciate ligament, or retrieval of loose bodies.197A.P. Apostolopoulos et al., The incidence of infrapatellar plicae in the elderly Welsh populationOgata and Uhtoff [17] performed an embryolo-gic study on over 116 knees regarding the develop-ment of synovial plicae in human knee joints. Accord-ing to Ogata’s results regarding the incidence, theinfrapatellar plica was the most frequent (50%).A progressive decrease in its incidence was noticedfrom 11 to 20 weeks of gestation, indicating, accord-ing to the authors, that the development of the jointcavity was still ongoing at the intercondylar notch [17].The prevalence of the infrapatellar plicae reportedin the literature also varies according to the type of im-aging studies performed. Brody et al. [2], on doublecontrast arthrography of 167 knees, reported 10.1% ofinfrapatellar plicae. According to Dalinka and Garofola[3], there used to be confusion between infrapatellarplica and an intact ACL during arthrography. Kosarekand Helms [13] reviewed retrospectively magnetic re-sonance images (MRI) of 1060 knee examinations thatwere performed in their institute in order to identifythe incidence of the infrapatellar plicae. All of these pa-tients underwent MRI for conditions and symptoms un-related to infrapatellar plicae. Of the 1060 MRI exami-nations only four infrapatellar plicae were detected. Theincidence of the infrapatellar plica was 0.4%, which dif-fers from the 65%, 38.5%, and 37.7% noted in the stud-ies by Kim, Ozcan, and ourselves, respectively. This dif-ference is possibly because anatomic studies can de-tect plicae that are extremely thin and may be beyondthe resolution of imaging.CONCLUSIONSThe clinical significance of the infrapatellar plica wasconsidered to be minimal. Nevertheless, recent studieshave proven that a pathologic infrapatellar plica cangive rise to symptoms. Additionally, an infrapatellar plicacan cause difficulties during arthroscopy to evaluate theACL, and can interfere when arthroscopically removinga loose body that is located in the intercondylar notch.Very few reports in the literature have recorded its inci-dence. In our study, the incidence of infrapatellar plicaein the elderly Welsh population suffering from kneeosteoarthritis was significantly lower when comparedto Kim’s study, which recorded the incidence of infra-patellar plicae in younger patients. Possibly, degenera-tive changes of the knee joint can cause resorption ofthe infrapatellar plica, decreasing, in this way, its inci-dence in the elderly population. However, it is not clearif this is caused by abnormal movement of the kneejoint, which can cause damage of the plica. Also, thenatural terrain of Wales may have an effect on this inci-dence. Wales has a lot of hills and people have to puta lot of pressure in their knees in order to climb stairs orhills daily. Future studies with a larger number of kneesamples and a greater range of age population couldgive more accurate results and explanations regardingthe incidence of the infrapatellar plicae. Also, patientsof non-hilly areas need to be examined in case our hy-pothesis is wrong.REFERENCES1. Boyd CR, Eakin C, Matheson GO (2005) Infrapatellar pli-ca as a cause of anterior knee pain. Clin J Sport Med, 15:98–103.2. Brody GA, Pavlov H, Warren RF, Ghelman B (1983) Plicasynovialis infrapatellaris: arthrographic sign of anteriorcruciate ligament disruption. AJR, 170: 1551–1555.3. Dalinka M, Garofola J (1976) The infrapatellar synovialfold: a cause for confusion in the evaluation of the ante-rior cruciate ligament. AJR, 127: 586–589.4. Dandy DJ (1990) Anatomy of the medial suprapatellar pli-ca and the medial synovial shelf. Arthroscopy, 6: 79–85.5. Demirag B, Ozturk C, Karakayali M (2006) Symptomaticinfrapatellar plica. Knee Surg Sports Trauma Arthrosc, 14:156–160.6. Dorchak JD, Barrack RL, Kneisl JS, Alexander AH (1991)Arthroscopic treatment of symptomatic synovial plica of theknee. Long term follow up. Am J Sports Med, 19: 503–507.7. Fullerton A (1916) The surgical anatomy of the synovialmembrane of the knee joint. Br J Surg, 4: 191–200.8. Jouanin T, Dupont JY, Halimi P, Lassau JP (1982) Thesynovial folds of the knee joint: anatomical study. AnatClin, 4: 47–53.9. Kellgren JH, Lawrence JS (1963) Atlas of standard radio-graphs of arthritis. Oxford Blackwell Scientific.10. Kim SJ, Choe WS (1997) Arthroscopic findings of thesynovial plicae of the knee. Arthroscopy, 13: 33–41.11. Kim SJ, Kim JY, Lee JW (2002) Pathologic infrapatellarplica. Arthroscopy, 18: E25.12. Kim SJ, Min BH, Kim HK (1996) Arthroscopic anatomy ofthe infrapatellar plica. Arthroscopy, 12: 561–564.13. Kosarek F, Helms C (1999) The MR appearance of theinfrapatellar plica. AJR, 172: 481–484.14. Lino S (1939) Normal arthroscopic findings in the kneejoint of adult cadavers. J Jpm Orthop Assoc, 14: 467–523.15. Mayeda T (1918) Ueber das Strangartige Gebilde in derKnigel-Enkhoele. (Chordi Cavi Articularis Genu) Mitt MedFak Kaisert Univ Tokio, 21: 507–553.16. Nakayama A, Sugita T, Aizawa T, Takahashi A, Honma T(2011) Incidence of medial plica in 3.889 knees in theJapanese population. Arthroscopy, 27: 1523–1527.17. Ogata S, Uhtoff H (1990) The development of synovialplicae in human knee joints: An embryologic study.Arthroscopy, 6: 315–321.18. Ozcan M, Copuroglou C, Ciftdemir M, Turan F, Calpur OU(2011) Does an abnormal infrapatellar plica of the kneeincrease the risk of chondral damage in the knee. KneeSur Sports Traum Arthrosc, 19: 218–221.19. Patel D (1978) Arthroscopy of the plicae synovial foldsand their significance. Am J Sports Med, 6: 217–225.20. Reider B, Marshall JL, Warren RF (1981) Persistent verticalseptum in the human knee joint. JBJS Am, 63: 1185–1187.21. Sakakibara J. (1976) Arthroscopic study on lino’s band-plicasynovialis mediopatelaris. 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THE INCIDENCE OF THE INFRAPATELLAR PLICAE IN THE ELDERLY WELSH POPULATION

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THE INCIDENCE OF THE INFRAPATELLAR PLICAE IN THE ELDERLY WELSH POPULATION

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