Medial Abrasion Syndrome: A Neglected Cause of Knee Pain in Middle and Old Age Shaw-Ruey Lyu, MD, PhD, Ching-Chih Lee, MD, PhD, and Chia-Chen Hsu, MD Abstract: Knee pain is a prevailing health problem of middle and old INTRODUCTION age. Medial plica-related medial abrasion syndrome (MAS), although a hronic knee pain is a prevalent health problem of middle 1 well-known cause of knee pain in younger individuals, has rarely been C and old age. It has been found to be significantly associ- investigated in older individuals. This prospective study was conducted ated with lower quality of life and is a major public health 2–4 to investigate the prevalence and clinical manifestations of this syn- issue. Effective prevention and early treatment of knee pain drome as a cause of knee pain in middle and old age. The outcomes of at these ages has a major influence on healthy aging in the 5 arthroscopic treatment for this syndrome were also evaluated. population. In the younger population, knee pain can have A total of 232 knees of 169 patients >40 years of age (41–82, many possible causes, with medial plica syndrome always 6 median: 63 years old) suffering from chronic knee pain were analyzed. mentioned in the differential diagnosis ; in contrast, osteoar- The clinical diagnosis, predisposing factors, presenting symptoms, and thritis (OA) is regarded as the most common cause of knee pain physical signs were investigated. The sensitivity and specificity of each in middle-aged and older people in addition to trauma-related parameter of the clinical presentation for the diagnosis of MAS were conditions, such as meniscus and/or ligament injury, crystal- evaluated after confirmation by arthroscopy. For patients with MAS, induced inflammatory arthropathy, and rheumatoid arthritis.7,8 the roentgenographic and arthroscopic manifestations were investi- Therefore, the issue of knee pain during middle and old age has gated, and arthroscopic medial release (AMR) was performed. The always been intermingled with OA in the literature.1–3,7,9,10 outcomes were evaluated by the changes in the pain domain of the Knee Although OA is the most common concomitant diagnosis Society scoring system and by patient satisfaction. The prevalence of of the patients with knee pain in this age group, the etiology and medial plica was 95%, and osteoarthritis (OA) was the most common mechanism of the pain have yet to be fully understood. Many clinical diagnosis. Symptoms of pain and crepitus in motion and local studies have been conducted to investigate the origin of pain in tenderness during physical examination were the most sensitive the OA knee,11–16 and they have reached the consensus that it is parameters for the diagnosis. A history of a single knee injury com- multifactorial, including psychosocial factors, mechanical fac- bined with local tenderness and a palpable band found during physical tors (eg, misalignment, valgus-varus laxity, body mass index, examination were the most specific parameters for the diagnosis. The and abnormal gait), subchondral bone abnormalities (eg, majority of patients suffering from this syndrome were successfully denuded subchondral bone and bone marrow lesions), and treated using AMR, yielding a satisfaction rate of 85.5% after a synovitis. Within these factors, synovitis has recently been minimum of 3 years. increasingly recognized as an important feature of the patho- MAS is a common cause of knee pain in middle and old age and physiology of the OA knee.17 It was not only proven to be can be effectively treated by AMR. Its concomitance with OA strongly correlated with knee pain severity18,19 but also con- warrants further investigation. sidered a predictive factor of subsequent advanced chondro- pathy in the OA knee.20 Therefore, synovitis treatment must be (Medicine 94(16):e736) considered when treating OA knee pain.21 The mediopatellar plica is a fold in the synovium that Abbreviations: AMR = arthroscopic medial release, KSS = Knee represents an embryologic remnant in the development of the Society scoring system, IL-1b = interleukin-1b, MAS = medial knee’s synovial cavity.22,23 Although the prevalence of medial abrasion syndrome, MMP-3 = matrix metalloproteinase-3, OA = plica ranges widely, from 22% to 95%,24–26 it is generally agreed osteoarthritis. that this structure can produce knee pain and can be successfully treated by arthroscopic resection in the event that it becomes inflamed, thickened, and/or less elastic.27–29 In a review of the literature, it appears to be only recognized as one of the main Editor: Worawit Louthrenoo. causes of knee pain in adolescents or young adults.23,25–30 With Received: October 9, 2014; revised: January 28, 2015; accepted: March 12, 31 2015. the exception of a small number of case reports, few studies From the Joint Center (SRL, CCH), Center for Clinical Epidemiology and have specified this well-known structure in their descriptions with Biostatistics (CCL), Dalin Tzu-Chi General Hospital, Chiayi, Taiwan; and regard to its presentation or clinical manifestation in older School of Medicine,Tzu-Chi University (SRL, CCL), Hualien, Taiwan. 32–36 Correspondence: Shaw-Ruey Lyu, Joint Center, Dalin Tzu-Chi General populations. Recent studies that investigated the chrono- Hospital, and 2, Min-Shen Road, Dalin, Chiayi 62247, Taiwan (e-mail: logical evolution of medial plicae disclosed that medial plica was [email protected]). more commonly found in patients with OA knees and that the This work was funded by the Clinical Research Grant Program of the severity of the degeneration was positively correlated with the Buddhist Dalin Tzu-Chi General Hospital. The authors have no conflicts of interest to disclose. severity of the medial plica and the patient age. According to Copyright # 2015 Wolters Kluwer Health, Inc. All rights reserved. these studies, the abrasion from repeated friction between the This is an open access article distributed under the Creative Commons medial plica and the facing medial femoral condyle during daily Attribution-NoDerivatives License 4.0, which allows for redistribution, activities would increase the severity of the pathologic change in commercial and non-commercial, as long as it is passed along unchanged and in whole, with credit to the author. the medial plica and give rise to clinical symptoms such as ISSN: 0025-7974 synovitis and pain. Surgical eradication of this abrasion could DOI: 10.1097/MD.0000000000000736 cure most patients’ pain and even decelerate or halt the Medicine Volume 94, Number 16, April 2015 www.md-journal.com | 1 Lyu et al Medicine Volume 94, Number 16, April 2015 degenerative process in their knees.37,38 However, there is no Snapping or Locking study in the literature that has focused on the clinical presentation A feeling of buckling or a sense of insecurity or pseudo- of medial plicae in middle-aged and older individuals. locking in a particular position, which mostly occurs when the In this study, the prevalence and clinical manifestations of knee is partially bent while bearing weight. Occasionally, medial plica-related medial abrasion syndrome (MAS) in a locking occurs when a patient stands up to walk after sitting population of middle-aged and older patients suffering from or lying down for a long period of time. The knee will unlock chronic knee pain were prospectively investigated. This syn- after standing for a few minutes. drome was evaluated and defined by its clinical manifestations, including predisposing factors, symptoms, signs, radiographic Signs manifestations, and arthroscopic findings. The clinical outcome 37 Localized Tenderness of pain relief by arthroscopic medial release (AMR) for this Precise tender area over the region between the inferior- syndrome was also investigated. We postulated that this syn- medial margin of the lower pole of the patella and the ridge of drome would be a common cause of knee pain in this age group the medial femoral condyle. and could be effectively treated using AMR. Palpable Band MATERIALS AND METHODS A palpable band with snapping or crepitation over the From March to August 2007, 176 consecutive patients >40 tender area mentioned earlier. years, with a total of 243 knees that had received arthroscopic surgery at our institute by the first author, were included in this Arthroscopic Surgery prospective study. All these patients were referred from other All procedures were performed under either spinal or gen- institutions with a given clinical diagnosis and had been treated eral anesthesia. During arthroscopic examination, special focus conservatively, including physical therapy and medication, for was placed on the presentation of the medial plica and the >1 year. For the 67 bilateral cases, each knee was evaluated as chondral lesions in the knee as clues for medial abrasion (see an individual case. Supplemental Video, http://links.lww.com/MD/A247, which demonstrates the medial abrasion phenomenon). The size and Preoperative Evaluation appearance of the medial plicae and the location and severity of The predisposing factors and presenting symptoms were the cartilaginous degeneration over the medial femoral condyle questioned and recorded by a nursing specialist for each knee. facing the medial plica were inspected and recorded according to The presenting physical signs of each knee were evaluated by Lyu and Hsu classification.34 The cartilaginous degeneration over the first author. During the history taking and physical exam- the medial, lateral, and patellofemoral compartments was ination, special attention was paid to the medial plica-related recorded based on the Outerbridge classification.39 To investigate items that are described in the next subsections. the relationship between the severity of the degeneration in different parts of the knee and that of the plical lesion, an arbitrary Predisposing Factors scoring system was defined to represent the severity of the Injuries cartilaginous degeneration on the medial femoral condyle facing The presentation of a single episode of injury, such as knee the medial plica, medial compartment, lateral compartment, buckling when it was suddenly bent, direct blunt injury over the patellofemoral joint, and the whole knee, as shown in Table 1.