The Knee 11 (2004) 103–108 0968-0160/04/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0968-0160 Ž 02 . 00143-6 Histological changes in the symptomatic mediopatellar plica Csaba Farkas *, Zoltan Hargitai , Levente Gaspar , Attila Kuki , Zoltan Csernatony , a, b a c a ´ ´ ´ ´ ´ Kalman Szepesi a ´ ´ Department of Orthopaedics, University of Debrecen, Medical and Health Science Centre, Nagyerdei krt. 98. H 4012 Debrecen, Hungary a Department of Pathology, University of Debrecen, Medical and Health Science Centre, Nagyerdei krt. 98. H 4012 Debrecen, Hungary b Department of Mathematics and Informatics, University of Debrecen, Medical and Health Science Centre, c Nagyerdei krt. 98. H 4012 Debrecen, Hungary Received 1 July 2002; received in revised form 6 September 2002; accepted 1 November 2002 Abstract One of the causes of anterior knee pain may be symptomatic mediopatellar plica. The pain is usually attributed to the mechanical damage caused by the plica inside the joint, or, more precisely, to the synovitis induced as a result. Recent observations seem to suggest, however, that the pain is, in addition, likely to be engendered by an increased number of nerve-elements present in the substance of the plica. The present study used up-to-date histochemical methods to reveal in the symptomatic mediopatellar plicae nerve-elements that may be made responsible for the pain. Semi-quantitative methods were used to establish the number of nerve-elements in the tissue samples obtained from 21 symptomatic mediopatellar plicae (Group ‘A’), exposing them to view with the aid of synaptophysin and neurofilament serum, coupled with routine light microscope as well as polarising microscope examinations following H&E and van Gieson staining. Tissue samples taken from the asymptomatic mediopatellar plica of 11 patients served as control (Group ‘B’). A significantly larger number of nerve-elements were found in the substance of the plicae of Group ‘A’ 6.9 (S.D."2.9) than in Group ‘B’ 3 (S.D."1.2). Within Group ‘A’, more nerve-elements were revealed in trauma- related case histories than in those with no recollections of trauma (an average of 9.6 vs. 5.2, respectively). Similarly, the reduction of pain achieved by surgery was greater in the trauma-related group than in the non-traumatic one (3.0 vs. 1.8, respectively). Relying on our observations, we claim that the painfulness of the knee joint plicae is in all probability also attributable to the fact that their tissue substance contains an increased number of nerve-elements. A major trauma in a particular case history contributes, in all likelihood, to an increase in the number of nerve-elements, but further examinations are required to clarify the pathomechanism involved.  2002 Elsevier Science B.V. All rights reserved. Keywords: Knee; Mediopatellar plica; Neural elements 1. Introduction Pipkin was the first to point out that, alongside with the usual causes of knee pain, such as lesions of the bone, the hyaline cartilage, the menisci and the ligament structures, plicae may also cause knee pain w14,15x. It is usually the mediopatellar plica that can be held responsible, although the suprapatellar plica might also be the cause of pain, as opposed to the infrapatellar and the lateral plica, which never induce pain. *Corresponding author. Department of Orthopaedic Surgery, Andras Josa Memorial County Hospital of Szabolcs-Szatmar-Bereg ´ ´ ´ County, Szent Istvan u. 68. H-4400 Nyiregyhaza, Hungary. Tel.: q ´ 36-42-465-566y1785. E-mail address: farkas@josa.szabinet.hu (C. Farkas). However, the mechanism of the development of knee pain caused by symptomatic plicae is not entirely clear. Some recent investigations furnished data on the various distributions of nerve-elements revealed by immunohis- tochemical methods in the soft tissues of the knee joint, which may play a role in the development of knee pain originating from these structures w21x. In this study, we aimed at discovering such patholog- ical histological changes in the substance of sympto- matic plicae, including their supply of nerve-elements, as may be held responsible for the development of painful plicae. The literature available provided no similar comparative histological examinations concern- ing symptomatic and asymptomatic plicae. The clinical