Arthrofibrosis After Total Knee Arthroplasty: A Critical Analysis Review.

¼ Arthrofibrosis after total knee arthroplasty (TKA) is the new formation of excessive scar tissue that results in limited ROM, pain, and functional deficits.¼ The diagnosis of arthrofibrosis is based on the patient's history, clinical examination, absence of alternative diagnoses from diagnostic testing, and operative findings. Imaging is helpful in ruling out specific causes of stiffness after TKA. A biopsy is not indicated, and no biomarkers of arthrofibrosis exist.¼ Arthrofibrosis pathophysiology is multifactorial and related to aberrant activation and proliferation of myofibroblasts that primarily deposit type I collagen in response to a proinflammatory environment. Transforming growth factor-beta signaling is the best established pathway involved in arthrofibrosis after TKA.¼ Management includes both nonoperative and operative modalities. Physical therapy is most used while revision arthroplasty is typically reserved as a last resort. Additional investigation into specific pathophysiologic mechanisms can better inform targeted therapeutics.

Can ultrasound replace MRI in diagnosing causes of ankle impingement in different compartments?

PURPOSE: This prospective study aims to determine the role of ultrasound (US) in diagnosing different types of ankle impingement due to osseous and soft tissue pathologies and to compare the results with magnetic resonance imaging (MRI), which is considered our gold standard. METHODS: The study population included 90 patients with unilateral ankle pain who presented with symptoms and signs suggestive of ankle impingement. Their age ranged from 17 to 57 years, with a mean age of 33.7 years. Using US and MRI, our cases were classified into bony and soft tissue ankle impingement. They were further classified according to the anatomical compartments affected, into anteromedial, anterior, anterolateral, posteromedial, and posterior. RESULTS: 90 patients were enrolled in this study: 51 males and 39 females. In our study, posterior ankle impingement was the commonest impingement type, while anteromedial ankle impingement was the rarest type, followed by posteromedial impingement. The accuracy of US in diagnosing osseous impingement was found to have the following: sensitivity 70.37%, specificity 100%, PPV 100%, NPV 75%, accuracy 84.31%, and p value < 0.001; meanwhile, the accuracy of US in diagnosing soft tissue impingement was found to have the following: sensitivity 83.33%, specificity 100%, PPV 100%, NPV 87.10%, accuracy 92.16%, and p value < 0.001. CONCLUSION: US is a good diagnostic tool in bone and soft tissue impingements, with a significant p value of 0.001 for both. US cannot replace MRI as a diagnostic tool, but as a widely available imaging modality, it can save time and cost and allows dynamic imaging.

Saucerization of complete discoid lateral meniscus is associated with change of morphology of the lateral femoral condyle and tibial plateau.

PURPOSE: To determine the effect of saucerization surgery on knee joint morphology associated with a complete discoid lateral meniscus (DLM) using magnetic resonance (MR) imaging. METHODS: This retrospective study included cases had undergone saucerization surgery for symptomatic DLM between 2007 and 2022. All cases were divided into two by age group: < 12 (U13) and > 13 (O13). The cases in the match group were randomly selected from preoperative cases in the O13 group matched with the age at the final follow-up (F/U) of cases in the U13 group. The following morphological parameters were evaluated using MR images preoperatively and at the final postoperative F/U in each group: anterior obliquity of the lateral tibial plateau (AOLTP), posterior obliquity of the lateral tibial plateau (POLTP), and the lowest point of the lateral femoral condyle (LPLFC). Each parameter was compared between the U13 preoperative (pre-OP) group and the O13 pre-OP group, the preoperative and final follow-up in the U13, and the U13 group at the final F/U and the match group preoperatively. RESULTS: A total of 77 cases were evaluated. 31 cases were in the U13 pre-OP group and 46 were in the O13 pre-OP group. With a minimal F/U of 2 years, 27 cases in the U13 group and 36 in the O13 group were included. The mean F/U period was 4.6 years in the U13 group and 3.2 years in the O13 group. 32 cases were included in the match group. In the match group, the inclination of the POLTP was significantly larger (P = 0.042) and the LPLFC was more lateral (P = 0.0034) than at the final F/U in the U13 group. CONCLUSIONS: Saucerization surgery for DLM in juvenile patients can prevent progression to the characteristic bone morphology DLM. These results could help the surgeon making the decision when the surgery would be performed for symptomatic DLM patients. LEVEL OF EVIDENCE: Retrospective comparative study; level of evidence, 3.

In major joint diseases the human synovium retains its potential to form repair cartilage.

The inner surface layer of human joints, the synovium, is a source of stem cells for the repair of articular cartilage defects. We investigated the potential of the normal human synovium to form novel cartilage and compared its chondrogenic capacity with that of two patient groups suffering from major joint diseases: young adults with femoro-acetabular impingement syndromes of the hip (FAI), and elderly individuals with osteoarthritic degeneration of the knee (OA). Synovial membrane explants of these three patient groups were induced in vitro to undergo chondrogenesis by growth factors: bone morphogenetic protein-2 (BMP-2) alone, transforming growth factor-ß1 (TGF-ß1) alone, or a combination of these two. Quantitative evaluations of the newly formed cartilages were performed respecting their gene activities, as well as the histochemical, immunhistochemical, morphological and histomorphometrical characteristics. Formation of adult articular-like cartilage was induced by the BMP-2/TGF-ß1 combination within all three groups, and was confirmed by adequate gene-expression levels of the anabolic chondrogenic markers; the levels of the catabolic markers remained low. Our data reveal that the chondrogenic potential of the normal human synovium remains uncompromised, both in FAI and OA. The potential of synovium-based clinical repair of joint cartilage may thus not be impaired by age-related joint pathologies.

The Role of Lubricin, Irisin and Exercise in the Prevention and Treatment of Osteoarthritis.

Osteoarthritis is a chronic degenerative musculoskeletal disease that worsens with age and is defined by pathological alterations in joint components. All clinical treatment recommendations for osteoarthritis promote exercise, although precise molecular pathways are unclear. The purpose of this study was to critically analyze the research on lubricin and irisin and how they relate to healthy and diseased joint tissue. Our research focused specifically on exercise strategies and offered new perspectives for future potential osteoarthritis treatment plans. Although lubricin and irisin have only recently been discovered, there is evidence that they have an impact on cartilage homeostasis. A crucial component of cartilage lubrication and integrity, lubricin is a surface-active mucinous glycoprotein released by the synovial joint. Its expression increases with joint movement. In healthy joints, lubricin molecules cover the cartilage surface to lubricate the boundary of the joint and inhibit protein and cell attachment. Patients with joint trauma, inflammatory arthritis, or genetically mediated lubricin deficiency, who do not produce enough lubricin to protect the articular cartilage, develop arthropathy. Irisin, sometimes known as the "sports hormone", is a myokine secreted primarily by skeletal muscle. It is a physiologically active protein that can enter the circulation as an endocrine factor, and its synthesis and secretion are primarily triggered by exercise-induced muscle contraction. We searched PubMed, Web of Science, Google Scholar, and Scopus using the appropriate keywords to identify the most recent research. The studies considered advance our knowledge of the role that exercise plays in the fight against osteoarthritis, serve as a valuable resource, and support the advancement of osteoarthritis prevention and therapy.

Use of Ultrasonography in Diagnosis of Medial Compartment Disease of the Elbow in Dogs.

OBJECTIVE: The objective of this prospective study was to evaluate the use of ultrasonography in the diagnosis of medial coronoid process disease in unclear cases. STUDY DESIGN: Fifteen elbows (on thirteen dogs) for which radiography and computed tomography did not lead to a clear diagnosis of medial coronoid process disease were included. On each elbow, ultrasonography was performed with a high frequency linear transducer (12-18Hz). Then, arthroscopic examination of the joint was performed by a surgeon who was unaware of ultrasonographic findings to confirm medial coronoid process disease. RESULTS: At least one ultrasonographic lesion was detected in 13 out of 15 elbows. The main reported ultrasonographic lesions were joint effusion (10/15 elbows) and an abnormal shape of the medial coronoid process (irregular, ill-defined or fragmented) (9/15). CONCLUSION: Ultrasonography can be a helpful additional diagnostic tool to confirm medial coronoid process disease of the elbow joint before performing arthroscopy in unclear cases. Further studies will be needed to evaluate the use of higher frequency transducers and determine if it could improve the diagnostic value of ultrasonography.

Arthroscopic surgery for symptomatic discoid lateral meniscus improves meniscal status assessed by magnetic resonance imaging T2 mapping.

INTRODUCTION: Discoid lateral meniscus (DLM) is an anatomic knee variant associated with increased tears and degeneration. This study aimed to quantify meniscal status with magnetic resonance imaging (MRI) T2 mapping before and after arthroscopic reshaping surgery for DLM. MATERIALS AND METHODS: We retrospectively reviewed the records of patients undergoing arthroscopic reshaping surgery for symptomatic DLM with ≥ 2-year follow-up. MRI T2 mapping was performed preoperatively and at 12 and 24 months postoperatively. T2 relaxation times of the anterior and posterior horns of both menisci and of the adjacent cartilage were assessed. RESULTS: Thirty-six knees from 32 patients were included. The mean age at surgery was 13.7 years (range 7-24), and the mean follow-up duration was 31.0 months. Saucerization alone was performed on five knees and saucerization with repair on 31 knees. Preoperatively, the T2 relaxation time of the anterior horn of the lateral meniscus was significantly longer than that of the medial meniscus (P < 0.01). T2 relaxation time significantly decreased at 12 and 24 months postoperatively (P < 0.01). Assessments of the posterior horn were comparable. The T2 relaxation time was significantly longer in the tear versus non-tear side at each time point (P < 0.01). There were significant correlations between the T2 relaxation time of the meniscus and that of the corresponding area of the lateral femoral condyle cartilage (anterior horn: r = 0.504, P = 0.002; posterior horn: r = 0.365, P = 0.029). CONCLUSIONS: The T2 relaxation time of symptomatic DLM was significantly longer than that of the medial meniscus preoperatively, and it decreased 24 months after arthroscopic reshaping surgery. The meniscal T2 relaxation time of the tear side was significantly longer than that of the non-tear side. There were significant correlations between the cartilage and meniscal T2 relaxation times at 24 months after surgery.

Immune cell populations differ in patients undergoing revision total knee arthroplasty for arthrofibrosis.

Arthrofibrosis following total knee arthroplasty (TKA) is a debilitating condition typically diagnosed based on clinical findings. To gain insight into the histopathologic immune cell microenvironment of arthrofibrosis, we assessed the extent of tissue fibrosis and quantified immune cell populations in specific tissue regions of the posterior capsule. We investigated specimens from three prospectively-collected, matched cohorts, grouped as patients receiving a primary TKA for osteoarthritis, revision TKA for arthrofibrosis, and revision TKA for non-arthrofibrotic, non-infectious reasons. Specimens were evaluated using hematoxylin and eosin staining, picrosirius red staining, immunofluorescence, and immunohistochemistry with Aperio®-based digital image analysis. Increased collagen deposition and increased number of α-SMA/ACTA2 expressing myofibroblasts were present in the arthrofibrosis group compared to the two non-arthrofibrotic groups. CD163 + macrophages were the most abundant immune cell type in any capsular sample with specific enrichment in the synovial tissue. CD163 + macrophages were significantly decreased in the fibrotic tissue region of arthrofibrosis patients compared to the patients with primary TKA, and significantly increased in adipose tissue region of arthrofibrotic specimens compared to non-arthrofibrotic specimens. Synovial CD117 + mast cells were significantly decreased in arthrofibrotic adipose tissue. Together, these findings inform diagnostic and targeted therapeutic strategies by providing insight into the underlying pathogenetic mechanisms of arthrofibrosis.

The role of intra-articular injection of autologous platelet-rich plasma versus corticosteroids in the treatment of synovitis in lumbar facet joint disease.

OBJECTIVES: To compare the efficacy between platelet-rich plasma (PRP) and corticosteroids (CS) in improving magnetic resonance imaging (MRI)-detected synovitis in correlation with clinical complaints among patients with lumbar facet joint (FJ) disease. METHODS: This study was carried out at Eldemerdash Hospital, Cairo, Egypt between September 2019 and January 2021. A prospective, randomized, comparative, single blinded study included 30 patients with lumbar FJ disease, divided into 2 equal groups, received PRP and CS injections. Patients were comparatively assessed before and after the intervention according to number of tender lumbar FJs, maximum active lumbar extension range of motion, LBP visual analogue score, LBP functional disability questionnaires and MRI lumbar FJ detected synovitis and their grading. RESULTS: Both groups showed a significant improvement in all mentioned parameters at follow-up after 3 months. However, PRP injections promoted better performance in terms of MRI synovitis grade in all lumbar FJ levels compared to CS injections. CONCLUSION: Both PRP and CS injections were effective in improving MRI-detected FJ synovitis while concurrently improving all examined parameters at follow-up after 3 months. However, PRP promoted better improvement in MRI-detected synovitis grade, suggesting that it may be a better treatment option for longer duration efficacy.TRN: NCT04860531- 1/3/2021.

Factors Predicting Poor Surgical Outcome in Patients with Thoracic Ossified Ligamentum Flavum - Analysis Of 106 Patients in a Tertiary Care Hospital in South India.

Background: Ossified ligamentum flavum (OLF) is the major cause of thoracic myelopathy in our locality. Surgical outcomes and their related factors for patients with thoracic OLF (T-OLF) remain unclear because of the few studies on this condition. Objectives: The present study aimed to examine the factors predicting poor surgical outcomes and the effectiveness of decompressive laminectomy and OLF resection in patients with T-OLF. Material and Methods: A total of 106 patients with T-OLF operated at our institute from 2007 to 2018 were included. The mJOA score was used in neurological assessment preoperatively and during the follow-up. Multiple regression analysis was conducted to know the best correlation between factors and surgical outcomes. Results: The mean mJOA score was 5.67 ± 2.13 preoperatively and 7.50 ± 2.60 postoperatively at the end of follow-up. The recovery rate was 43.29 ± 30.55%. After decompressive laminectomy, the mean mJOA score, modified Nurick score, and Ashworth's grade showed significant improvement (P < 0.001). Multiple regression analysis showed that the age of the patient, associated trauma, OLF level, tuberous type OLF, intramedullary signal change on T2WI, preoperative severity of myelopathy, pre-op mJOA score, and pre-op Nurick grade were significantly correlated with the surgical outcome (P < 0.001). No correlation was identified with the duration of symptoms, dural ossification, dural tear, and CSF leak (P > 0.05). Conclusion: It is important to identify preventable risk factors for poor surgical outcomes for T-OLF. Age of the patient, associated trauma, OLF level, tuberous type OLF, intramedullary signal change on T2WI, preoperative severity of myelopathy, preoperative mJOA score, and Nurick grade were important predictors of surgical outcome in our study series.

Discoid Meniscus.

Discoid meniscus is the most common congenital variant of the meniscus. Its variability in pathology leads to a spectrum of clinical presentations in patients. Treatment must be tailored to the specific pathology of the discoid meniscus. Imaging studies such as radiographs and magnetic resonance imaging can be useful in confirming the diagnosis, but may be the most accurate in determining specific pathology. Thorough intraoperative evaluation of the discoid is critical to appropriate surgical management. Rim preservation and repair is preferred to prevent degenerative changes in the knee.

Arthrofibrosis - a myth or true joint disorder?

Authors, mostly specialists on rehabilitation and orthopedic surgery prove that arthrofibrosis is a commonly overlooked phenomenon, which may lead to serious limitation in the range of movement, leading to limitation in patients quality of functioning. The main goal of this article is to emphasize the importance of understanding a such complex condition. Non typical patomechanism, lack of biomarkers dedicated to this dysfunction and general lack of understanding in this pathology causes that risk factors and the most effective strategies remain vastly unknown. Pathophysiology of the arthrofibrosis in the joints is definitely multifactorial, but intense production of collagen seems to be the main factor. Most modern pharmacological methods concentrate on the regulation of collagen fiber production and reducing the inflammation. Inflammation from joint contractures stimulates the proliferation of activated cells that results in the production of extracellular matrix macromolecules to form fibrotic tissue that is deposited into the capsule, thereby resulting in fibrosis. Lack of unified classification scale is caused by relatively high variation of the functions fulfilled by particular joints and each treatment plan should be constructed individually. Quality of surgical treatment and physical therapy play a major role in both prevention and treatment of such complex condition as arthrofibrosis. Both iatrogenic mistakes and overly aggressive manual therapy are some of main factors increasing the risk of this pathological condition. Introducing properly conducted physical therapy treatment in the early stage is crucial to main the range of movement and preventing this significant problem.

Management of arthrofibrosis in neuromuscular disorders: a review.

Arthrofibrosis, or rigid contracture of major articular joints, is a significant morbidity of many neurodegenerative disorders. The pathogenesis depends on the mechanism and severity of the precipitating neuromuscular disorder. Most neuromuscular disorders, whether spastic or hypotonic, culminate in decreased joint range of motion. Limited range of motion precipitates a cascade of pathophysiological changes in the muscle-tendon unit, the joint capsule, and the articular cartilage. Resulting joint contractures limit functional mobility, posing both physical and psychosocial burdens to patients, economic burdens on the healthcare system, and lost productivity to society. This article reviews the pathophysiology of arthrofibrosis in the setting of neuromuscular disorders. We describe current non-surgical and surgical interventions for treating arthrofibrosis of commonly affected joints. In addition, we preview several promising modalities under development to ameliorate arthrofibrosis non-surgically and discuss limitations in the field of arthrofibrosis secondary to neuromuscular disorders.

Facet overhang: A novel parameter in the pathophysiology of multifidus muscle atrophy.

The relationship between degenerative zygapophysial joint (facet) arthropathy and multifidus muscle atrophy has not been rigorously evaluated. The purpose of this study was to determine if specific morphological features of degenerative facet arthropathy are correlated with multifidus muscle atrophy. We retrospectively reviewed medical records and imaging studies of patients with lumbar spinal stenosis. Facet overhang, bridging osteophyte formation, facet effusion, and facet angles were evaluated by univariable and multivariable regression to identify independent associations with deep and superficial parts of the multifidus total cross-sectional area (tCSA), functional cross-sectional area (fnCSA), and fatty infiltration (FI). Facet overhang was classified as severe in 50 females (53.2%) versus 56 males (36.9%) (p = 0.030). Severity of facet overhang and female sex were independently associated with smaller deep part of the multifidus tCSA and fnCSA as well as higher FI, reflecting greater atrophy of the deep region compared to total muscle mass. In comparison, severe facet overhang (p < 0.001; OR = 3.47, 95% CI = 2.13-5.66) and female sex (p < 0.001; OR = 4.19, 95% CI = 2.58-6.79) were independently associated only with higher superficial part of the multifidus FI, reflecting muscle steatosis without significant lean muscle atrophy. In patients with degenerative lumbar spinal stenosis, facet overhang is an independent risk factor for deep part of the multifidus atrophy. Bridging osteophyte formation, facet effusion, and facet angles were not independently associated with deep part of the multifidus atrophy.

Editorial Commentary: It Is Imperative to Fix Symptomatic Hip Gluteus Medius Tears at Time of Femoroacetabular Impingement: Why Ignore This Pain in the Butt?

The hip can have a multitude of different pathologies leading to different symptoms. Greater trochanteric pain syndrome, historically attributed to bursitis, has been largely found to be associated with lesions of the gluteus medius and minimus tendons, and the prevalence of gluteus medius pathology in patients with femoroacetabular impingement (FAI) is as high as one-third of the FAI population. If a patient is found to have significant clinical symptoms of both FAI and a gluteus medius tear, it is imperative to fix both pathologies. The most important diagnostic predictor in hip arthroscopy is not magnetic resonance imaging but a well-executed history and physical exam. We use a quadrant approach: the medial quadrant accounts for adductor bursitis, adductor tears, pudendal neuralgia, or sports hernias. The posterior quadrant may account for a hamstring tear, lumbar radiculopathy, ischiofemoral impingement, or in rare cases piriformis syndrome. The anterior quadrant accounts for more intraarticular pathologies including FAI, Labral tears, osteoarthritis, avascular necrosis, or iliopsoas bursitis. The lateral quadrant would include greater trochanteric pain syndrome, gluteus medius and minimus tears, external snapping hip syndrome and iliotibial band syndrome. By using this systematic approach and using the magnetic resonance imaging to confirm the diagnosis, we may accurately determine patients' hip pathologies.

Localized tenosynovial giant cell tumor: a rare case of snapping hip.

We report on a 40-year-old male with a 9-month-long history of snapping of his right hip caused by a previously undescribed etiology of internal extra-articular snapping hip, namely due to a localized tenosynovial giant cell tumor. Both dynamic ultrasound evaluation and MRI proved to be crucial in the diagnosis of this rare entity. Auto-provocation of the snapping showed an anterior hip mass moving posteriorly to the psoas tendon which elucidated the pain and clicking sensation. Subsequent MRI demonstrated a peripheral low-intensity rim due to hemosiderin deposition around the synovial mass which is indicative for pigmented villonodular tenosynovitis. Treatment consisted of arthroscopic shaver burr resection. Immediately postoperatively, the snapping sensation could not be provoked anymore by the patient. The purpose of reporting on this case report is to emphasize several successive learning points. First, dynamic ultrasound aids in diagnosis and differentiation of the types of snapping hip. Second, specific MRI features are suggestive of tenosynovial giant cell tumor, recognizing these traits may prevent delayed diagnosis and subsequent aggravated clinical course. Third, localized pigmented villonodular tenosynovitis around the hip may present as an internal extra-articular snapping hip and is of consideration in the differential diagnosis of recurrent snapping hip.

Knee Plical Pathology and Impingement Syndromes.

Impingement syndromes are caused by anatomic variability of normal structures, altered biomechanics, or a combination of both. Imaging manifestations of painful impingement syndromes can explain patient symptoms and guide appropriate management. This article discusses the MR imaging findings associated with synovial plica syndrome and other impingement syndromes of the knee joint. Relevant embryology and anatomic variation of synovial plicae are presented, with emphasis on features predisposing to patient symptoms. The most common knee impingement syndromes are reviewed including iliotibial band fraction syndrome, Hoffa fat pad impingement/lateral patellar tendon lateral femoral condyle friction syndrome, and suprapatellar/quadriceps fat pad impingement.

Concomitant lipoma arborescens and synovial osteochondromatosis of the knee.

Intra-articular masses are not a rare finding in routine imaging. This is particularly true in patients with underlying joint diseases such as degenerative arthritis. Nevertheless, concomitant presentation is rather uncommon in imaging studies. The authors report an unusual concomitant lipoma arborescens and synovial osteochondromatosis (which has not previously been reported in the literature to the best of the authors' knowledge) in a man in his 60 s with a long-standing history of knee osteoarthritis. In this case presentation, we review the differential diagnosis for noninfectious synovial proliferative disorders presenting as intra-articular masses, their potential association with underlying joint pathology, and discuss the key imaging features and appropriate treatment.

Patella-patellar tendon angle in relation to the medial patellar plica syndrome, chondromalacia patella, and infrapatellar fat pad syndrome.

The patella-patellar tendon angle (PPTA) assessing the sagittal patellar tilt was reported to be related with anterior knee pain. Herein, clinical effect of PPTA in patients with medial patellar plica (MPP) syndrome, chondromalacia patella, and infrapatellar fat pad (IPFP) syndrome, the most common causes of anterior knee pain, was evaluated. In this retrospective study, 156 patients with anterior knee pain who underwent magnetic resonance imaging (MRI) and arthroscopic surgery that confirmed isolated MPP syndrome, chondromalacia patella, or IPFP syndrome from June 2011 to January 2021 were included in the study group and 118 patients without knee pathology on MRI during the same period were included in the control group. The PPTA was measured on knee MRI and compared between the two groups. A receiver operating characteristic (ROC) analysis was used to evaluate the value of PPTA for predicting the risk of patellofemoral joint disorder. The mean PPTA was significantly smaller in study group (138.1 ± 4.2°) than control group (142.1 ± 4.3°) (p < 0.001). However, there was no significant difference in PPTA among the patients with MPP syndrome, chondromalacia patella, and IPFP syndrome. Furthermore, the ROC analysis revealed that the area under curve, sensitivity, and specificity for predicting the risk of patellofemoral joint disorders were 0.696, 70.3% and 57.6%, respectively, at a PPTA cutoff of 138.3°. Therefore, the smaller PPTA may be associated with MPP syndrome, chondromalacia patella, and IPFP syndrome. Furthermore, PPTA could be a predictive factor for the risk of patellofemoral joint disease in patients with anterior knee pain.

E8002 Reduces Adhesion Formation and Improves Joint Mobility in a Rat Model of Knee Arthrofibrosis.

Knee arthrofibrosis is a common complication of knee surgery, caused by excessive scar tissue, which results in functional disability. However, no curative treatment has been established. E8002 is an anti-adhesion material that contains L-ascorbic acid, an antioxidant. We aimed to evaluate the efficacy of E8002 for the prevention of knee arthrofibrosis in a rat model, comprising injury to the surface of the femur and quadriceps muscle 1 cm proximal to the patella. Sixteen male, 8-week-old Sprague Dawley rats were studied: in the Adhesion group, haemorrhagic injury was induced to the quadriceps and bone, and in the E8002 group, an adhesion-preventing film was implanted between the quadriceps and femur after injury. Six weeks following injury, the restriction of knee flexion owing to fibrotic scarring had not worsened in the E8002 group but had worsened in the Adhesion group. The area of fibrotic scarring was smaller in the E8002 group than in the Adhesion group (p < 0.05). In addition, the numbers of fibroblasts (p < 0.05) and myofibroblasts (p < 0.01) in the fibrotic scar were lower in the E8002 group. Thus, E8002 reduces myofibroblast proliferation and fibrotic scar formation and improves the range of motion of the joint in a model of knee injury.