Surface Markers and Chemokines/Cytokines of Tumor-Associated Macrophages in Osteosarcoma and Other Carcinoma Microenviornments-Contradictions and Comparisons.

Osteosarcoma (OS) is the most common primary bone tumor in children and adolescents. Prognosis is improving with advances in multidisciplinary treatment strategies, but the development of new anticancer agents has not, and improvement in prognosis for patients with pulmonary metastases has stalled. In recent years, the tumor microenvironment (TME) has gained attention as a therapeutic target for cancer. The immune component of OS TME consists mainly of tumor-associated macrophages (TAMs). They exhibit remarkable plasticity, and their phenotype is influenced by the TME. In general, surface markers such as CD68 and CD80 show anti-tumor effects, while CD163 and CD204 show tumor-promoting effects. Surface markers have potential value as diagnostic and prognostic biomarkers. The cytokines and chemokines produced by TAMs promote tumor growth and metastasis. However, the role of TAMs in OS remains unclear to date. In this review, we describe the role of TAMs in OS by focusing on TAM surface markers and the TAM-produced cytokines and chemokines in the TME, and by comparing their behaviors in other carcinomas. We found contrary results from different studies. These findings highlight the urgency for further research in this field to improve the stalled OS prognosis percentages.

Chronic dislocations of the fourth and fifth carpometacarpal joints with successful treatment by ligament repair: A case report and literature review.

Dislocations of the fourth and fifth carpometacarpal joints (CMCJs) are rare and often misdiagnosed via radiography. Moreover, treatment strategies have not yet been standardized. Herein, we report a case of chronic dislocations of the fourth and fifth CMCJs with delayed diagnosis and successful treatment via ligament repair. A 29-year-old male patient who was initially diagnosed with contusion at another center following a fall on the stairs was referred to our hospital one month later due to persistent pain and swelling. Fourth and fifth CMCJ dislocations were diagnosed using radiography and computed tomography. Closed reduction attempts were unsuccessful, prompting open reduction. The operative findings included rupture of the dorsal carpometacarpal ligament and hamate cartilage injury. Using two mini anchors, the fourth and fifth dorsal carpometacarpal ligaments were repaired, and Kirschner-wire (K-wire) pinning was performed. The K-wire was extracted after four weeks. At the eight-month follow-up, the only remaining symptom was mild discomfort, and the range of motion and grip strength was fully recovered. Our findings highlight the difficulties in diagnosing CMCJ dislocation and suggest ligament repair as a treatment option for chronic cases of CMCJ dislocation.

IgG4-related disease with subcutaneous involvement and the associated diagnostic challenges with MRI.

IgG4-related disease is a rare fibroinflammatory disorder characterized by the infiltration of IgG4-rich plasma cells. Herein, we report a case of IgG4-related disease of the subcutaneous tissue with atypical MRI findings and difficulties in the histopathological examination using needle biopsy. Based on the clinical presentation and MRI findings, the patient was diagnosed with a benign myxoid or cystic tumor. Additionally, histopathological findings from a needle biopsy suggested a myxoma. Therefore, the correct diagnosis of IgG4-related disease was not made preoperatively. The resected specimens confirmed IgG4-related disease with an IgG4/IgG ratio > 80%. Previous reports have shown that the MRI findings of IgG4-related disease mimic both malignancy and inflammation; surprisingly, the features of subcutaneous IgG-related disease, including tail sign, unclear border, and heterogeneous enhancement, were similar to those found in sarcoma. Therefore, histopathological findings are needed for a correct diagnosis. Furthermore, careful examination is essential because the neoplasm and inflammation may overlap with IgG4-related disease, and needle biopsy is not fully reflective of the tumor. As is highlighted in the present case, IgG4-related disease is often misdiagnosed; therefore, clinicians should adequately recognize that even if the histopathological findings in biopsy were consistent with those observed in the MRI, misdiagnosis may occur.

Delayed Achilles Tendon Rupture at 17 Years of Age After Treatment of Clubfoot with Ponseti Method: A Case Report.

CASE: Traumatic pediatric Achilles ruptures are rare, and few cases have been reported among patients with a history of Achilles tenotomy. A 17-year-old boy with a history of Achilles tenotomies for congenital clubfoot as an infant presented with acute midsubstance Achilles tendon rupture of the right leg. The gastrocnemius fascia was dissected to allow for approximation of the ruptured Achilles tendon segments. Furthermore, the plantaris tendon was harvested and sutured around the Achilles tendon-rupture site to improve strength. CONCLUSIONS: Patients with a history of clubfoot and chronic Achilles tendon pain should be alerted to the risk of Achilles tendon rupture.

Hereditary Anatomical Risk Factors for Anterior Cruciate Ligament Injuries.

INTRODUCTION:  Genetic and anatomical factors have been reported as risk factors for anterior cruciate ligament (ACL) injuries. This study aimed to investigate anatomical characteristics in family members sustaining ACL injuries, compared with age- and sex-matched patients with simple meniscus injuries. MATERIALS AND METHODS:  Medical records of 1548 patients who underwent ACL reconstruction were reviewed. Cases of ACL injury occurring in first-degree relatives were selected. Forty-one patients from 20 families were included in the study (F-ACL group). Fifty patients with meniscus injuries were included as controls. Anatomical factors comprising posterior-inferior tibial slope (PITS), notch width index (NWI), notch angle (NA), and intercondylar notch roof inclination angle (RA) were compared between groups. The correlation of these anatomical factors between parent and child or siblings was also investigated. RESULTS:  The 41 patients (20 families) consisted of 12 parent-child pairs and 29 siblings (13 pairs and one trio). Injuries occurred during playing the same sport in 11 families (55%). PITS was significantly steeper in the F-ACL group (9.9 vs. 7.8 degrees). NWI and NA were significantly smaller in the F-ACL group (0.262 vs. 0.278 and 50.5 vs. 58.8 degrees). RA was significantly greater in the F-ACL group (130 vs. 126.9 degrees). A positive correlation in NA (r = 0.677) and a weak correlation in NWI and RA were observed between family members. CONCLUSIONS:  Common anatomical risk factors of ACL injury exist within families, including intercondylar notch stenosis and steep posterior tibial slope. The findings suggest the potential for developing effective ACL injury prevention programs targeting these risk factors.

Impacts of Segond Fractures on Anterior Cruciate Ligament Reconstruction Outcomes.

INTRODUCTION: Segond fractures, characterized by avulsion injuries at the lateral tibial condyle's anterolateral structure (ALS) attachment, often coincide with anterior cruciate ligament (ACL) injuries, potentially leading to knee instability. However, the influence of Segond fractures on knee stability after ACL reconstruction remains uncertain. Despite documented ALS reconstructions, there is a lack of consensus regarding the assessment of ALS failure and the criteria for surgical interventions. This study aimed to determine if Segond fracture presence impacts ACL reconstruction outcomes, utilizing patient-reported subjective assessments and healthcare providers' objective evaluations. MATERIALS AND METHODS: This retrospective study encompassed 639 patients (328 males, 311 females; mean age 26.9 years) who underwent ACL reconstruction, with a follow-up of at least one year. Subjects were divided into two groups: Segond fractures diagnosed through radiographic findings (Group S+, n = 17) and no Segond fractures (Group S-, n = 622). Clinical evaluation included the 36-item Short Form Survey (SF-36), Lysholm score, visual analog scale (VAS) for knee pain, knee injury and osteoarthritis outcome score (KOOS), and knee instability assessment via Telos SE (Telos Japan, Tokyo, Japan). Statistical comparisons were performed between the two groups. RESULTS: At the final follow-up, all SF-36 subscales improved in all eight subscales compared to before surgery, reaching national standard scores; no significant inter-group differences were evident. Lysholm scores were 93.0 ± 12.1 (Group S+) and 91.7 ± 10.9 (Group S-) (P = 0.62), VAS for knee pain was 10.0 ± 18.0 (Group S+) and 11.9 ± 16.9 (Group S-) (P = 0.62), total KOOS was 89.0 ± 17.4 (Group S+) and 90.7 ± 9.9 (Group S-) (P = 0.39), and anterior tibial translation differences were 2.8 ± 3.0 mm (Group S+) and 2.7 ± 2.9 mm (Group S-) (P = 0.73). All these values represent postoperative measurements. No significant discrepancies existed between groups across evaluation methods. CONCLUSIONS: This study's results suggest that Segond fractures have minimal impact on clinical ACL reconstruction outcomes, as assessed through both patient-reported subjective evaluations and objective healthcare provider evaluations. Segond fractures' significance in postoperative outcomes questions the necessity of ALS reconstruction.

Bilateral Patellofemoral Ligament Reconstruction for Patellar Instability in Ehlers-Danlos Syndrome: A Case Report.

CASE: We report the case of an 11-year-old boy with Ehlers-Danlos syndrome (EDC) who exhibited simultaneous medial and lateral patellar instability. The patient presented with a medial patellar dislocation, and subsequently, the patella became very unstable both medially and laterally. Despite distal realignment, the patellar instability was so significant that he underwent simultaneous reconstruction of the medial and lateral patellofemoral ligament using the semitendinosus tendon, with a good result. CONCLUSION: Simultaneous reconstruction of the medial and lateral patellofemoral ligament is an effective method in cases of extreme patellar instability, such as the EDS case.

Case Report: Angiomatoid fibrous histiocytoma in the hand: a rare clinical presentation and diagnostic challenge.

Angiomatoid fibrous histiocytoma (AFH) is a rare tumor of mesenchymal origin occurring in young adults. Based on its clinical course, it is said to have an intermediate potential. We present a case of a 59-year-old woman with AFH in the hand that was difficult to diagnose. A benign soft tissue tumor was suspected on magnetic resonance imaging, and its size and open biopsy suggested nodular fasciitis or inflammatory myofibroblastic tumor. A diagnosis of AFH was eventually made based on the analysis of the resected specimens. The characteristic findings of histopathology and immunohistochemistry in this case were relatively poor, so fluorescence in situ hybridization contributed to making the correct diagnosis. Considering its prognosis, careful follow-up was decided upon without additional surgery. Our case is a challenging one because of its atypical presentation and inconclusive imaging and histopathological findings.

Synovial chondromatosis: Rare involvement of metacarpophalangeal joint and diagnostic challenges in MR imaging.

Synovial chondromatosis (SC) is a rare benign tumor of the cartilaginous tissue that frequently affects large joints intra-articularly. Characteristic imaging findings were reported for the diagnosis of SC. Herein, we report a case of SC of the metacarpophalangeal joint with atypical MRI findings. Considering the clinical presentation, erosion, absence of calcification on X-ray and CT, and low intensity on short tau inversion recovery (STIR), tenosynovial giant cell tumor was the initially diagnosis. However, histopathological findings revealed SC with fibrosis, which was confirmed using Elastica Van Gieson (EVG) staining. In general, low intensity on STIR in SC indicate calcification; however, it can also represent fibrosis in SC. In this case, the diagnosis of SC using MRI was limited highlighting the importance of histopathological findings for an accurate diagnosis of SC.

Relationship between floating toes condition and lower limb muscle weight in 8-year-old children: the Yamanashi adjunct study of the Japan Environment and Children's Study (JECS-Y).

[Purpose] Floating toe is a condition in which the toes make insufficient contact with the ground. Weak muscle strength is reportedly one cause of floating toe. However, little evidence exists regarding the relationship between foot muscle strength and floating toe. Here we examined the relationship between foot muscle strength and floating toe by investigating the children' lower extremity muscle mass and floating toe conditions. [Participants and Methods] This cohort study enrolled 118 8-year-old children (62 females, 56 males) with recorded footprints and muscle mass evaluations using dual-energy X-ray absorptiometry. We calculated the floating toe score using the footprint. We measured the muscle weights and the muscle weights divided by the lengths of the lower limbs separately on the left and right sides using dual-energy X-ray absorptiometry. [Results] No significant correlations were observed between the floating toe score and muscle weights or muscle weights divided by lower-limb lengths for either gender or side. [Conclusion] In this study, no significant correlation was found between floating toe degree and lower limb muscle mass, suggesting that lower limb muscle strength is not the primary cause of floating toe, at least in children.

Is histopathological synovitis score a predictor of postoperative requirement for additional or alternative drug treatment in the patients with rheumatoid arthritis?

OBJECTIVES: Histopathological synovitis scoring is useful for assessing activity in patients with rheumatoid arthritis (RA) at sampling, but it is unclear whether it can be a predictor of future drug treatment. The purpose of this study was to examine whether histopathological synovitis score is a predictor of postoperative requirement for additional or alternative drug treatment after total knee arthroplasty (TKA). METHODS: Thirty patients with RA in whom synovial samples were obtained during TKA were included. Patients were divided into the drug treatment enhanced group (EG), which included patients who needed additional or alternative drug treatment within 1 year after TKA, and the drug treatment maintenance group (MG). The Rooney synovitis score (RSS) was compared between groups. Logistic regression analysis was performed to clarify prognostic factors for postoperative drug treatment change. RESULTS: The total RSS was significantly higher in the EG than in the MG (29.3 vs 15.1; P < .001). Multivariate analysis showed that total RSS and swollen joint counts were independent variable associated with postoperative requirement for additional or alternative drug treatment (P < .05). CONCLUSIONS: Histopathological synovitis scoring may predict requirement for additional or alternative drug treatment in patients with RA after TKA.

The Anatomical Position of Graf's Standard Plane and Its Relationship With Pelvic Morphology: A Computed Tomography-Based Study.

Objective The Graf method is the most widely used ultrasonographic method for evaluating developmental dysplasia of the hip (DDH), and it relies on a set standard plane. However, no previous reports have discussed the detailed anatomical location of the plane. The aim of this study was to evaluate the exact anatomical position of Graf's standard plane in the pelvis and to ascertain the correlation between this position and pelvic morphology in children without abnormal pelvic morphology. Methods We retrospectively assessed the pelvic CT data of 32 children (64 hips) aged three to five years without abnormal pelvic morphology and measured the pelvic winging and acetabular anteversion and coverage. We defined the coronal plane that passed through the center of the bilateral femoral head as plane A. We determined that Graf's standard plane could be approximated by rotating plane A until the outer wall of the ilium was parallel to the sagittal plane, and we defined this as plane A'. AA' was defined as the angle from plane A to plane A' on the sagittal plane. The anterior rotational angle (clockwise, viewing from the right side) was measured as the positive AA'. Moreover, we measured the pelvic rotation, acetabular anteversion, and acetabular coverage and evaluated the correlation between AA' and these morphological parameters. Results The average AA' was -8.27° and AA' had a significant correlation with acetabular anteversion (Spearman's ρ=0.40**, p<0.01). Conclusions We found that Graf's standard plane, as determined by the CT scan, tilts slightly posteriorly. This information may be useful in improving the ease of ultrasonographic examination of DDH.

Validity of a fall risk assessment score sheet for patients hospitalized in general wards.

Falls (including fall on same level and fall to a lower level) are frequent medical accidents among hospitalized patients. We investigated the status of falls in our hospital, aiming to verify the usefulness of a fall risk assessment sheet and identify the risk factors of falls. 5219 patients who were admitted to the general wards of our hospital between April 2016 and March 2019 were studied. Patient background data and the result of risk assessment based on a fall risk assessment score sheet at admission were registered. The frequency and location of falls during hospitalization, and the impact on patients were investigated. Risk factors for falls were analyzed based on the assessment results at admission. 218 falls occurred during hospitalization in 152 of 5219 patients (2.9%). The most common location of falls was bedside (68%). Falls occurred at night in 28%. The impact of falls was level 1 in 18 patients, level 2 in 117, level 3a in 11, and level 3b in 6 (all had head injuries, and one had concurrent fracture). Fall rate was 1.1% (41/3791 patients) at risk level I, 6.8% (91/1335 patients) at level II, and 21.5% (20/93 patients) at level III. Multiple logistic regression analysis identified age, history of fall, tendency to act without pressing nurse call button, unstable gait, unstable when standing, and use of narcotic as risk factors of falls. The incidence of falls at our hospital was lower compared to previous reports, and fall risk assessment was useful overall.

Risk Factors for Long Bone Fractures in Patients with Severe Motor and Intellectual Disabilities: A 6-year Follow-up Retrospective Study.

Objectives: We investigated the clinical situation of fractures that occurred in patients in the severely disabled patients' ward of our hospital. The study aimed to identify risk factors for the occurrence of long bone fractures in the extremities, which pose problems in nursing care. Methods: We retrospectively studied fractures that occurred between April 2015 and March 2021 among a total of 126 patients in the severely disabled patients' ward of our hospital. The fracture site, frequency of occurrence, cause of injury, and other parameters were investigated. We statistically compared the fracture group and non-fracture group with respect to age, sex, body position before fracture, motor function, food intake status, body mass index, use of anti-epileptic drugs, hip dislocation, and maximum extension angle and range of motion of elbow/knee joints. Results: Among 126 patients, a total of 35 fractures occurred in 28 patients (22%). There were 19 long bone fractures of the extremities in 17 patients. Multiple logistic regression analysis using the occurrence of long bone fractures of the extremities as the objective variable identified the following significant independent variables: age [odds ratio (OR)=1.087, P=0.008], maximum extension angle of the elbow joint (OR=1.039, P=0.023), range of motion of the elbow joint (OR=0.940, P=0.003), and range of motion of the knee joint (OR=0.972, P=0.034). Conclusions: This study reveals that older age and flexion contracture of elbow and knee joints are risk factors for the occurrence of long bone fractures in severely disabled patients.

A cross-sectional study on the correlations between floating toe, plantar arch posture, and body composition in 8-year-old children.

BACKGROUND: Floating toe (FT): inadequately in contact with the ground and flexible flat foot (FFF) are frequently seen in children. According to some reports, inadequate foot muscle strength may cause FT or FFF.Therefore, a relationship may exist between arch formation, FT, and pedal muscle strength. This study aimed to evaluate the correlation of FT with plantar arch posture and body composition, including overall muscle mass. METHODS: We conducted our own cohort study in addition to the Japan Environment and Children's Study conducted by the Ministry of the Environment, Japan. Out of 705 eight-year-old children participating in this adjunct study, 578 with recorded footprints were included. Body composition (body weight, body fat percentage, and predicted muscle mass) was assessed using body composition analyzer. Presence of FT or FFF was evaluated using foot pressure plate. We calculated the FT score (small FT score indicates insufficient ground contact of the toes) and the Chippaux-Smirak Index (CSI) using images of the plantar footprint. RESULTS: The FT score (an indicator of FT) showed no significant correlation with CSI (an indicator of plantar arch posture). Moreover, no significant correlations between the predicted muscle mass, FT score, and CSI were observed. CONCLUSIONS: This is the first report that assessed the relationship of FT with plantar arch posture and body composition in children. This study indicated that muscle strength might not be a major factor for FT and FFF development in children.

Differences of 2-year longitudinal changes of locomotive syndrome among patients treated with thoracolumbar interbody fusion, total hip arthroplasty, and total knee arthroplasty for degenerative diseases.

OBJECTIVES: To clarify the longitudinal changes in patients with preoperative Stage-3 locomotive syndrome (LS) according to different types of surgeries, we investigated the changes in the LS stage in patients who underwent surgery for degenerative musculoskeletal diseases. METHODS: A prospective cohort study was conducted on 168 patients with degenerative diseases [46 spinal deformities treated with thoracolumbar interbody fusion (T/LIF), 86 hips with osteoarthritis treated with total hip arthroplasty (THA), and 36 knees with osteoarthritis treated with total knee arthroplasty (TKA)]. The results for the LS stage, stand-up test, two-step test, and 25-question Geriatric Locomotive Function Scale (GLFS-25) were evaluated preoperatively and at 6 months, 1 year, and 2 years postoperatively. RESULTS: Preoperatively, most patients had Stage-3 LS (89.1, 90.8, and 80.6% in the T/LIF, THA, and TKA groups, respectively). At 2 years postoperatively, the Stage-3 LS improved in 41.5, 75.6, and 55.2% of patients in the T/LIF, THA, and TKA groups, respectively. All groups showed similar improvements in the two-step test. The THA group showed the best result in the GLFS-25. CONCLUSIONS: LS stage improved in different patterns over 2 years postoperatively and the LS risk test revealed differences in postoperative movement ability according to the type of surgery.

Prevalence of floating toe and its relationship with static postural stability in children: The Yamanashi adjunct study of the Japan Environment and Children's Study (JECS-Y).

Floating toe (FT) is a frequently seen condition in which a toe is inadequately in contact with the ground. Although toes play an important role in stabilizing standing posture and walking, many aspects of the effects of FT on the body remain unclear. To our knowledge, there have been no reports about the relationship between FT and postural stability, especially in children. This study aimed to clarify the prevalence of FT and its relationship with static postural stability in children. Of the 400 children aged 8 years who participated in our cohort study, 396, who were examined for static postural stability, were included in this study. Postural stability and FT were assessed using a foot pressure plate. The sway path length of the center of pressure and the area of the ellipse defined as the size of the area marked by the center of pressure, were measured as an evaluation of static postural stability. We calculated the "floating toe score (FT score: small FT score indicates insufficient ground contact of the toes)" using the image of the plantar footprint obtained at the postural stability measurement. The rate of FT was elevated at more than 90%, and the FT score in the eyes-closed condition was significantly higher than that in the eyes-open condition in both sexes. The FT score significantly correlated with the center of pressure path and area. Our results suggest that ground contact of the toes is not directly related to static postural stability in children, but it may function to stabilize the body when the condition becomes unstable, such as when the eyes are closed.

A Rare Case of an Iliac Fracture at the Iliac Fossa Immediately after Salter Innominate Osteotomy.

This report presents the unusual case of a 5-year-old girl with iliac fracture just after Salter innominate osteotomy for developmental dysplasia of the hip. The iliac fracture was diagnosed two days after Salter innominate osteotomy, and computed tomography (CT) revealed that it was at the extremely thin portion of the iliac wing called the "iliac fossa." We were able to reduce the fracture by pulling the left leg distally, and after reducing the iliac bone, the ilium was fixed by Kirschner wire from the anteroinferior iliac spine and anterosuperior iliac spine. The patient was in a hip-spica cast for 6 weeks postoperatively and allowed to walk from 3 months after the surgery. At the last follow-up one year after the surgery, bone union was completely obtained, and she had no complications. The cause of the fracture seems to be the stress concentration on the iliac fossa due to the cranked iliac osteotomy line passing through the iliac fossa. The current case indicates the importance of careful evaluation by CT before surgery and ensuring that the osteotomy line does not extend near the iliac fossa.

Improvement of locomotive syndrome after total hip arthroplasty: A two-year longitudinal cohort study.

OBJECTIVES: Patients requiring total hip arthroplasty (THA) may possibly have locomotive syndrome (LS). Therefore, we investigated changes of LS in patients undergoing THA and clarified key factors that affected LS stage. METHODS: A prospective cohort study was conducted with 88 patients undergoing THA (74 females, 14 males, mean age: 67.6 years). Data collected using LS stage, stand-up test, two-step test, and 25-question Geriatric Locomotive Function Scale results were evaluated before THA, and 6 months, 1 year, and 2 years after THA. Key factors were determined using multivariate analysis and receiver operating characteristic (ROC) curve analysis. RESULTS: Before THA, all patients had fallen LS (stage1: 3.4% and stage2: 96.6%). Overall, 56.8% patients improved their LS stage, and 17.0% of patients overcame LS at 2 years after THA. The key factors that affected LS stage were preoperative two-step test and age. ROC analyses showed a preoperative two-step test score of 0.988 and an age of 67.5 years as a cut-off value for the change of LS stage. CONCLUSIONS: Patients experiencing LS due to hip disorders have the potential to recover after THA. Additional postoperative training may be beneficial for patients with low preoperative two-step test scores to improve their LS stage.

Pathological features of established osteoarthritis with hydrathrosis are similar to rheumatoid arthritis.

OBJECTIVES: The prevalence of rheumatoid arthritis (RA) and knee osteoarthritis (OA) is increasing with our aging society. Some reports suggest that OA with effusion synovitis develops into RA and early OA patients with effusion are pathologically similar to those with RA. The purpose of this study was to examine the relationship between histological features of established knee OA with or without effusion and RA. METHODS: Seventy-nine patients in which synovial specimens were obtained during total knee arthroplasty were included. Patients were divided into an RA group, OA with effusion (OA+) group, and OA without effusion (OA-) group. The Rooney synovitis score and serum matrix metalloproteinase (MMP)-3 levels were compared among groups. We also examined the correlation between the Rooney synovitis score and its sub-scores with MMP-3 levels. RESULTS: The total Rooney score was significantly higher in the RA group than in the OA+ and OA- groups (25.4 vs 17.1, p < 0.01; 25.4 vs 13.5, p < 0.001, respectively). This score also was significantly higher in the OA+ group than in the OA- group (p < 0.05). The proliferating blood vessels score, perivascular infiltrates of lymphocytes score, focal aggregates of lymphocytes score, and diffuse infiltrates of lymphocytes score were significantly higher in the RA group than in the OA- group (7.05 vs 3.29, 4.95 vs 3.43, 3.29 vs 1.46, and 2.26 vs 1.18, respectively; p < 0.05), but not compared with the OA+ group. The total Rooney score demonstrated a significantly positive correlation with serum MMP-3 levels in the RA group (r = 0.61; 95% CI: 0.28 to 0.81; p < 0.01) and in the OA+ group (r = 0.57; 95% CI: 0.24 to 0.78; p < 0.01). CONCLUSIONS: Previous reports showed the histological similarity between RA and early OA with effusion. We confirmed this histological similarity, in particular the distribution of lymphocytes, between RA and established OA with effusion. It is possible that cases diagnosed as OA with effusion might progress to overt RA. KEY POINTS: • Histological similarity was observed between RA and established OA with effusion.