Degree of synovitis on MRI by comprehensive whole knee semi-quantitative scoring method correlates with histologic and macroscopic features of synovial tissue inflammation in knee osteoarthritis

Association between synovial tissue damage and pain in late-stage knee osteoarthritis: A cross-sectional study

OBJECTIVE

To identify the presence and distribution of histopathological features of synovial inflammation and tissue damage, and to test their associations with ultrasound (US) imaging measures of synovitis and patient-reported measures of pain in knee osteoarthritis (OA).

DESIGN

In the cross-sectional study of 122 patients undergoing surgery for painful late-stage (Kellgren-Lawrence Grade 3 or 4) knee OA, we compared US measures of synovitis (n = 118) and pain (Knee Injury and Osteoarthritis Outcome Score) to histopathological measures of inflammation vs. synovial tissue damage in synovial tissue biopsies. Associations of histopathological features with US measures of inflammation or pain were assessed using linear or logistic regression while controlling for covariates.

RESULTS

Histopathological features of inflammation were associated with higher odds of moderate/severe US synovitis (odds ratio [OR] = 1.34 [95%CI 1.04, 1.74), whereas features of synovial tissue damage were associated with lower odds of moderate/severe US synovitis (OR = 0.77 [95%CI 0.57, 1.03]). Worse histopathological scores for synovial tissue damage were associated with more pain (-1.47 [95%CI -2.88, -0.05]), even while adjusting for synovial inflammation (-1.61 [95%CI -3.12, -0.10]).

CONCLUSIONS

Synovial tissue damage is associated with pain in late-stage knee OA, independent from inflammation and radiographic damage. These novel findings suggest that preventing synovial tissue damage may be an important goal of disease-modifying OA therapy.

Acacetin targets STING to alleviate the destabilization of the medial meniscus-induced osteoarthritis in mice

Osteoarthritis (OA) is a common joint disorder affecting about 7% of the global population, primarily characterized by the gradual loss of articular cartilage. This degeneration results from local inflammation, matrix depletion, and direct cartilage damage. A critical element in this process is the activation of the stimulator of the interferon genes (STING) pathway. Emerging evidence highlights its potential as a therapeutic target, with natural products showing promise as inhibitors. Our study centers on Acacetin, a basic unit of polyketides known for its anti-inflammatory properties. Prior research has highlighted its potential interaction with STING based on the structure. Thus, this study aimed to assess the effectiveness of Acacetin as a STING inhibitor and its protective role against OA. In vitro experiments showed that Acacetin pretreatment not only mitigated interleukin-1β (IL-1β)-induced cytotoxicity but also decreased the inflammatory response and degeneration in chondrocytes stimulated IL-1β. In vivo studies revealed that Acacetin administration significantly reduced articular cartilage destruction, abnormal bone remodeling, and osteophyte formation in a model of OA induced by destabilization of the medial meniscus (DMM). Mechanistically, Acacetin was found to interact directly with STING, and inhibit IL-1β-induced activation of STING, along with the subsequent phosphorylation of the TBK1/NF-κB pathway in chondrocytes. In conclusion, our findings establish Acacetin as an effective inhibitor of STING that protects chondrocytes from IL-1β-induced damage and slows the progression of OA in mice.

Research progress on nanotechnology of traditional Chinese medicine to enhance the therapeutic effect of osteoarthritis

Osteoarthritis (OA) is a prevalent chronic condition that primarily impacts the articular cartilage and surrounding bone tissue, resulting in joint inflammation and structural deterioration. The etiology of OA is multifaceted and intricately linked to the oxidative stress response of joint tissue. Oxidative stress (OS) in OA leads to the creation of reactive oxygen species (ROS) and other oxidizing agents, resulting in detrimental effects on chondrocytes. This oxidative damage diminishes the flexibility and robustness of cartilage, thereby expediting the progression of joint deterioration. Therefore, the antioxidant effect is crucial in the treatment of OA. Currently, a considerable number of components found in traditional Chinese medicine (TCM) have been scientifically demonstrated to exhibit remarkable antioxidant and anti-inflammatory properties. Nevertheless, the utilization of this program is considerably constrained as a result of intrinsic deficiencies, notably stability concerns. The successful amalgamation of TCM components with nanotechnology has properly tackled these concerns and enhanced the efficacy of therapeutic results. The objective of this study is to delineate the antioxidant characteristics of nano-TCM and assess the current inventory of literature pertaining to the application of nano-TCM in the treatment of OA. In conclusion, this paper will now turn to the constraints and potential avenues for the advancement of nano-TCM within the realm of OA therapy.

A standardized approach to evaluation and reporting of synovial histopathology in two surgically induced murine models of osteoarthritis

OBJECTIVE

Synovial pathology has been linked to osteoarthritis (OA) pain in patients. Microscopic grading systems for synovial changes in human OA have been described, but a standardized approach for murine models of OA is needed. We sought to develop a reproducible approach and set of minimum recommendations for reporting of synovial histopathology in mouse models of OA.

METHODS

Coronal and sagittal sections from male mouse knee joints subjected to destabilization of medial meniscus (DMM) or partial meniscectomy (PMX) were collected as part of other studies. Stains included Hematoxylin and Eosin (H&E), Toluidine Blue (T-Blue), and Safranin O/Fast Green (Saf-O). Four blinded readers graded pathological features (hyperplasia, cellularity, and fibrosis) at specific anatomic locations. Inter-reader agreement of each feature score was determined.

RESULTS

There was acceptable to very good agreement when using 3-4 individual readers. After DMM and PMX, expected medial predominant changes in hyperplasia and cellularity were observed, with fibrosis noted at 12 weeks post-PMX. Synovial changes were consistent from section to section in the mid-joint area. When comparing stains, H&E and T-blue resulted in better agreement compared to Saf-O stain.

CONCLUSIONS

To account for the pathologic and anatomic variability in synovial pathology and allow for a more standardized evaluation that can be compared across studies, we recommend evaluating a minimum set of 3 pathological features at standardized anatomic areas. Further, we suggest reporting individual feature scores separately before relying on a single summed "synovitis" score. H&E or T-blue are preferred, inter-reader agreement for each feature should be considered.

Recommendations For a Standardized Approach to Histopathologic Evaluation of Synovial Membrane in Murine Models of Experimental Osteoarthritis

Background

Synovial pathology has been linked to osteoarthritis (OA) pain in patients. Microscopic grading systems for synovial changes in human OA have been described, but a standardized approach for murine models of OA is needed. We sought to develop a reproducible approach and set of minimum recommendations for synovial histopathology in mouse models of OA.

Methods

Coronal and sagittal sections from male mouse knee joints subjected to destabilization of medial meniscus (DMM) or partial meniscectomy (PMX) were collected as part of other studies. Stains included Hematoxylin and Eosin (H&E), Toluidine Blue (T-Blue) and Safranin O/Fast Green (Saf-O). Four blinded readers graded pathological features (hyperplasia, cellularity, and fibrosis) at specific anatomic locations in the medial and lateral compartments. Inter-reader reliability of each feature was determined.

Results

There was acceptable to very good agreement between raters. After DMM, increased hyperplasia and cellularity and a trend towards increased fibrosis were observed 6 weeks after DMM in the medial locations, and persisted up to 16 weeks. In the PMX model, cellularity and hyperplasia were evident in both medial and lateral compartments while fibrotic changes were largely seen on the medial side. Synovial changes were consistent from section to section in the mid-joint area mice. H&E, T-blue, and Saf-O stains resulted in comparable reliability.

Conclusions

To allow for a standard evaluation that can be implemented and compared across labs and studies, we recommend using 3 readers to evaluate a minimum set of 3 pathological features at standardized anatomic areas. Pre-defining areas to be scored, and reliability for each pathologic feature should be considered.

Oral Administration of Protease-Soluble Chicken Type II Collagen Ameliorates Anterior Cruciate Ligament Transection-Induced Osteoarthritis in Rats

This study investigated whether oral supplementation with protease-soluble chicken type II collagen (PSCC-II) mitigates the progression of anterior cruciate ligament transection (ACLT)-induced osteoarthritis (OA) in rats. Eight-week-old male Wistar rats were randomly assigned to the following groups: control, sham, ACLT, group A (ACLT + pepsin-soluble collagen type II collagen (C-II) with type I collagen), group B (ACLT + Amano M-soluble C-II with type I collagen), group C (ACLT + high-dose Amano M-soluble C-II with type I collagen), and group D (ACLT + unproteolyzed C-II). Various methods were employed to analyze the knee joint: nociceptive tests, microcomputed tomography, histopathology, and immunohistochemistry. Rats treated with any form of C-II had significant reductions in pain sensitivity and cartilage degradation. Groups that received PSCC-II treatment effectively mitigated the ACLT-induced effects of OA concerning cancellous bone volume, trabecular number, and trabecular separation compared with the ACLT alone group. Furthermore, PSCC-II and unproteolyzed C-II suppressed ACLT-induced effects, such as the downregulation of C-II and upregulation of matrix metalloproteinase-13, tumor necrosis factor-α, and interleukin-1β. These results indicate that PSCC-II treatment retains the protective effects of traditional undenatured C-II and provide superior benefits for OA management. These benefits encompass pain relief, anti-inflammatory effects, and the protection of cartilage and cancellous bone.

Culture-expanded mesenchymal stromal cell therapy: does it work in knee osteoarthritis? A pathway to clinical success

Osteoarthritis (OA) is a degenerative multifactorial disease with concomitant structural, inflammatory, and metabolic changes that fluctuate in a temporal and patient-specific manner. This complexity has contributed to refractory responses to various treatments. MSCs have shown promise as multimodal therapeutics in mitigating OA symptoms and disease progression. Here, we evaluated 15 randomized controlled clinical trials (RCTs) and 11 nonrandomized RCTs using culture-expanded MSCs in the treatment of knee OA, and we found net positive effects of MSCs on mitigating pain and symptoms (improving function in 12/15 RCTs relative to baseline and in 11/15 RCTs relative to control groups at study endpoints) and on cartilage protection and/or repair (18/21 clinical studies). We examined MSC dose, tissue of origin, and autologous vs. allogeneic origins as well as patient clinical phenotype, endotype, age, sex and level of OA severity as key parameters in parsing MSC clinical effectiveness. The relatively small sample size of 610 patients limited the drawing of definitive conclusions. Nonetheless, we noted trends toward moderate to higher doses of MSCs in select OA patient clinical phenotypes mitigating pain and leading to structural improvements or cartilage preservation. Evidence from preclinical studies is supportive of MSC anti-inflammatory and immunomodulatory effects, but additional investigations on immunomodulatory, chondroprotective and other clinical mechanisms of action are needed. We hypothesize that MSC basal immunomodulatory "fitness" correlates with OA treatment efficacy, but this hypothesis needs to be validated in future studies. We conclude with a roadmap articulating the need to match an OA patient subset defined by molecular endotype and clinical phenotype with basally immunomodulatory "fit" or engineered-to-be-fit-for-OA MSCs in well-designed, data-intensive clinical trials to advance the field.

Macroscopic aspects of glenohumeral synovitis are related to rotator cuff tear severity

BACKGROUND

The microscopic pattern of inflammatory mediators associated with rotator cuff pathology is well documented; however, little is known regarding the contemporary presence of macroscopic inflammatory joint involvement. Our aim was to investigate shoulder synovitis in a large group of patients with different sized rotator cuff tears (RCTs) and to correlate the degree of macroscopic inflammatory changes of the glenohumeral joint with RCT severity.

MATERIALS AND METHODS

A total of 296 consecutive patients (169 F, 127 M; mean age ± standard deviation: 60.75 ± 7.91) submitted to arthroscopic RCT repair were enrolled. RCT was classified intraoperatively. Glenohumeral synovitis was investigated according to 4 parameters (Davis classification 2017: capsule color, villous projections, capillaries, and axillary recess). A total score was calculated, and a 3-grade severity scale was introduced. Statistics was performed.

RESULTS

Intraclass correlation coefficient (ICC) results show good to excellent reliability: capsule color (ICC: 0.95; 95% confidence interval [CI]: 0.89-0.99), villous projections (ICC: 0.90; 95% CI: 0.85-0.95), capillaries (ICC: 0.91; 95% CI: 0.86-0.95), and axillary recess (ICC: 0.55; 95% CI: 0.80-0.89).The synovitis total score was found to be 1.47 ± 1.16, 2.86 ± 1.84, and 3.99 ± 1.64 in patients with type I, II, and III RCTs, respectively. A significant difference was found between groups (P < .001). The prevalence of all the examined parameters was found to be significantly different between the different sized RCT groups (capsule color: P < .001; villous projections: P < .001; capillaries: P < .001; and axillary recess: P < .001). According to a 3-grade severity scale, the prevalence of absent, mild, and severe glenohumeral synovitis significantly differed between the RCT severity groups (P < .001).

CONCLUSIONS

The present study demonstrated that synovitis is a constant finding of rotator cuff pathology; it is present in 75% of patients with RCTs and correlates with tear severity. Whether synovitis is the cause or effect of RCT is still questionable. Further studies are also needed to better understand its role as a pain generator, as documented in other diseases.

Synovial inflammation in osteoarthritis progression

Osteoarthritis (OA) is a progressive degenerative disease resulting in joint deterioration. Synovial inflammation is present in the OA joint and has been associated with radiographic and pain progression. Several OA risk factors, including ageing, obesity, trauma and mechanical loading, play a role in OA pathogenesis, likely by modifying synovial biology. In addition, other factors, such as mitochondrial dysfunction, damage-associated molecular patterns, cytokines, metabolites and crystals in the synovium, activate synovial cells and mediate synovial inflammation. An understanding of the activated pathways that are involved in OA-related synovial inflammation could form the basis for the stratification of patients and the development of novel therapeutics. This Review focuses on the biology of the OA synovium, how the cells residing in or recruited to the synovium interact with each other, how they become activated, how they contribute to OA progression and their interplay with other joint structures.

The histopathological synovitis score is influenced by biopsy location in patients with knee osteoarthritis

INTRODUCTION

Osteoarthritis (OA) and rheumatoid arthritis (RA) represent the most common forms of arthritis, which are mainly caused by mechanical and inflammatory components, respectively. Determination of synovial inflammation in synovial biopsies via the histopathological Krenn score may be crucial for correct diagnosis and treatment. Specifically, it remains unclear whether synovitis scores differ among multiple biopsy locations within a single joint.

MATERIALS AND METHODS

Eighty synovial samples were taken from four standardized regions of the knee in 20 patients (ten primary OA, ten secondary OA) undergoing total knee arthroplasty (TKA) or total synovectomy. The Krenn synovitis score (grade 0-9) was determined in a blinded manner by two expert pathologists in all biopsies. Next to the inter-rater reliability, we evaluated the agreement of the determined scores among the four biopsy locations within each knee.

RESULTS

The inter-rater reliability between the two pathologists was very high (Cohen's kappa = 0.712; r = 0.946; ICC = 0.972). The mean synovitis score was significantly higher in knees with secondary than in primary OA (p = 0.026). Importantly, we found clear differences between the scores of the four different biopsy locations within the individual knee joints, with an average deviation of 10.6%. These deviations were comparable in knees with primary and secondary OA (p = 0.64).

CONCLUSIONS

While we confirmed the synovitis score as a reliable and reproducible parameter to assess the histopathological synovitis grade in the knee, the considerable variability within the joint indicates that multiple synovial biopsies from different regions should be obtained to enable reliable results of the synovitis score.

Prolidase expression in knee osteoarthritis and healthy controls: Observational study

Prolidase enzyme activity is important for collagen resynthesis. In late stages of osteoarthritis (OA) its activity is decreased.To evaluate prolidase expression in knees of patients undergoing total arthroplasty for OA, and compare with young people undergoing knee arthroscopy due to traumatic injuries.In this cross-sectional study we included 20 patients with OA grade IV who underwent total knee arthroplasty and 20 controls of young patients who underwent arthroscopy for another reason besides OA. All participants were evaluated by knee ultrasound before the procedure. During the procedure, synovial tissue biopsies were taken and analyzed by immunofluorescence to search inflammation. Measures of central tendency, dispersion measures and position measures were used for the case of quantitative variables. Student t test or Mann-Whitney U test, and the logistic regression of Cox, was used.Prolidase expression in the synovial biopsy was significantly lower in the OA group than in the controls (0.017 ± 0.009 vs 0.062 ± 0.094, P < .05). Power Doppler (PD) signal was present in the synovitis of all knee recesses of the OA group in grayscale and in 17 (85%) of knees. The mean of the micro-vessel count in patients with OA was significantly higher vs controls (11 + 5.3 vs 4 + 2.1, P = .001). The neovascularization correlated significantly with the presence of PD signal in patients with OA (1.16, 95% CI, 1.02-1.34, P = .02).The prolidase expression in the synovial membrane evaluated by immunofluorescence, in patients with late stages of knee OA, is low, which may be interpreted as an evidence of decreased collagen resynthesis.

Triggers for acute flare in adults with, or at risk of, knee osteoarthritis: a web-based case-crossover study in community-dwelling adults

OBJECTIVE

To identify proximate causes ('triggers') of flares in adults with, or at risk of, knee osteoarthritis (OA), estimate their course and consequences, and determine higher risk individuals.

METHODS

In this 13-week web-based case-crossover study adults aged ≥40 years, with or without a recorded diagnosis of knee OA, and no inflammatory arthropathy who self-reported a knee flare completed a questionnaire capturing information on exposure to 21 putative activity-related, psychosocial and environmental triggers (hazard period, ≤72 h prior). Comparisons were made with identical exposure measurements at four 4-weekly scheduled time points (non-flare control period) using conditional logistic regression. Flare was defined as a sudden onset of worsening signs and symptoms, sustained for ≥24 h. Flare characteristics, course and consequence were analysed descriptively. Associations between flare frequency and baseline characteristics were estimated using Poisson regression.

RESULTS

Of 744 recruited participants (mean age [SD] 62.1 [10.2] years; 61% female), 376 reported 568 flares (hazards) and provided 867 valid control period measurements. Thirteen exposures (eight activity-related, five psychosocial/environmental) were positively associated with flare onset within 24 h (strongest odds ratio estimate, knee buckling: 9.06: 95% confidence interval [CI] 5.86, 13.99; weakest, cold/damp weather: 1.45: 95%CI 1.12, 1.87). Median flare duration was 5 days (IQR 3, 8), less common if older (incident rate ratio [IRR] 0.98: 95%CI 0.97, 0.99), more common if female (IRR 1.85: 95%CI 1.43, 2.39).

CONCLUSIONS

Multiple activity-related, psychosocial and environmental exposures are implicated in triggering flares. This evidence can help inform prevention and acute symptom management for patients and clinicians.

Detection of knee synovitis using non-contrast-enhanced qDESS compared with contrast-enhanced MRI

Background

To assess diagnostic accuracy of quantitative double-echo in steady-state (qDESS) MRI for detecting synovitis in knee osteoarthritis (OA).

Methods

Patients with different degrees of radiographic knee OA were included prospectively. All underwent MRI with both qDESS and contrast-enhanced T1-weighted magnetic resonance imaging (CE-MRI). A linear combination of the two qDESS images can be used to create an image that displays contrast between synovium and the synovial fluid. Synovitis on both qDESS and CE-MRI was assessed semi-quantitatively, using a whole-knee synovitis sum score, indicating no/equivocal, mild, moderate, and severe synovitis. The correlation between sum scores of qDESS and CE-MRI (reference standard) was determined using Spearman’s rank correlation coefficient and intraclass correlation coefficient for absolute agreement. Receiver operating characteristic analysis was performed to assess the diagnostic performance of qDESS for detecting different degrees of synovitis, with CE-MRI as reference standard.

Results

In the 31 patients included, very strong correlation was found between synovitis sum scores on qDESS and CE-MRI (ρ = 0.96, p < 0.001), with high absolute agreement (0.84 (95%CI 0.14–0.95)). Mean sum score (SD) values on qDESS 5.16 (3.75) were lower than on CE-MRI 7.13 (4.66), indicating systematically underestimated synovitis severity on qDESS. For detecting mild synovitis or higher, high sensitivity and specificity were found for qDESS (1.00 (95%CI 0.80–1.00) and 0.909 (0.571–1.00), respectively). For detecting moderate synovitis or higher, sensitivity and specificity were good (0.727 (95%CI 0.393–0.927) and 1.00 (0.800–1.00), respectively).

Conclusion

qDESS MRI is able to, however with an underestimation, detect synovitis in patients with knee OA.

Therapeutic options for targeting inflammatory osteoarthritis pain

Pain is the major symptom of osteoarthritis (OA) and is an important factor in strategies to manage this disease. However, the current standard of care does not provide satisfactory pain relief for many patients. The pathophysiology of OA is complex, and its presentation as a clinical syndrome is associated with pathologies of multiple joint tissues. Inflammation is associated with both OA pain and disease outcome and is therefore a major treatment target for OA and OA pain. Unlike TNF inhibitors and IL-1 inhibitors, established drugs such as glucocorticoids and methotrexate can reduce OA pain. Although central nociceptive pathways contribute to OA pain, crosstalk between the immune system and nociceptive neurons is central to inflammatory pain; therefore, new therapies might target this crosstalk. Newly identified drug targets, including neurotrophins and the granulocyte-macrophage colony-stimulating factor (GM-CSF)-CC-chemokine ligand 17 (CCL17) chemokine axis, offer the hope of better results but require clinical validation.

Are contrast-enhanced and non-contrast MRI findings reflecting synovial inflammation in knee osteoarthritis: a meta-analysis of observational studies

OBJECTIVE

To determine the correlation between knee synovitis assessed on contrast-enhanced (CE) and non-contrast enhanced (NCE) magnetic resonance imaging (MRI) with histology in patients with knee osteoarthritis.

METHODS

A comprehensive literature search was performed, and related articles published through July 2018 were extracted. Spearman correlation coefficients of MRI-based scores with histology reports were pooled using random effects model. To evaluate presence of publication bias, Egger test was performed.

RESULTS

Of 2377 identified records, eight studies consisting of 246 MRI exams were included. Two studies reported results of dynamic CE (DCE)-MRI examinations (81 knees) and two studies reported results of NCE-MRI. There were moderate positive correlations between CE-MRI scores and macroscopic (r = 0.53 (95% Confidence Interval (CI):0.37-0.66), P < 0.001) as well as microscopic (r = 0.56 (0.39-0.69), P < 0.001) histology. DCE-MRI were strongly correlated (r = 0.71 (0.58-0.80), P-value<0.001), with microscopic histology reports, while the correlation for NCE-MRI was low positive (r = 0.44 (0.20-0.63), P < 0.001). Meta-regression analysis showed that pooled correlation coefficients of DCE-MRI were significantly higher than CE-MRI (Slope = 0.29, SE = 0.13, P-value = 0.02). CE-MRI were also correlated with inflammatory infiltrate (r = 0.42), while the correlations for cell number of synovial lining (r = 0.27) and level of fibrosis (r = 0.29, P < 0.001) were very low.

CONCLUSION

Static and dynamic CE-MRI evaluation of knee synovitis were positively correlated with macroscopic and microscopic features of synovial membrane inflammation. Among the features of synovial tissue inflammation, CE-MRI scores correlated best with the inflammatory infiltrates of synovial tissue. Paucity of current evidence warrants further studies to assess performance of NCE-MRI on determining knee synovitis.

Infrapatellar fat pad abnormalities are associated with a higher inflammatory synovial fluid cytokine profile in young adults following ACL tear

OBJECTIVE

To evaluate the degree of knee fat pad abnormalities after acute anterior cruciate ligament (ACL) tear via magnetic resonance fat pad scoring and to assess cross-sectionally its association with synovial fluid biomarkers and with early cartilage damage as quantified via T1ρ and T2 relaxation time measurements.

DESIGN

26 patients with acute ACL tears underwent 3T MR scanning of the injured knee prior to ACL reconstruction. The presence and degree of abnormalities of the infrapatellar (IPFP) and the suprapatellar (SPFP) fat pads were scored on MR images along with grading of effusion-synovitis and synovial proliferations. Knee cartilage composition was assessed by 3T MR T1ρ and T2 mapping in six knee compartments. We quantified concentrations of 20 biomarkers in synovial fluid aspirated at the time of ACL reconstruction. Spearman rank partial correlations with adjustments for age and gender were employed to evaluate correlations of MR, particularly cartilage composition and fat pad abnormalities, and biomarker data.

RESULTS

The degree of IPFP abnormality correlated positively with the synovial levels of the inflammatory cytokine markers IFN-γ (ρpartial = 0.64, 95% CI (0.26-0.85)), IL-10 (ρpartial = 0.47, 95% CI (0.04-0.75)), IL-6 (ρpartial = 0.56, 95% CI (0.16-0.81)), IL-8 (ρpartial = 0.49, 95% CI (0.06-0.76)), TNF-α (ρpartial = 0.55, 95% CI (0.14-0.80)) and of the chondrodestructive markers MMP-1 and -3 (MMP-1: ρpartial = 0.57, 95% CI (0.17-0.81); MMP-3: ρpartial = 0.60, 95% CI (0.21-0.83)). IPFP abnormalities were significantly associated with higher T1ρ and T2 values in the trochlear cartilage (T1ρ: ρpartial = 0.55, 95% CI (0.15-0.80); T2: ρpartial = 0.58, 95% CI (0.18-0.81)) and with higher T2 values in the medial femoral, medial tibial as well as in patellar cartilage (0.45 ≤ ρpartial ≤ 0.59). Correlations between SPFP abnormalities and synovial markers were not significant except for IL-6 (ρpartial = 0.57, 95% CI (0.17-0.81)).

CONCLUSIONS

This exploratory study suggests that acute ACL rupture can be associated with damage to knee tissues such as the inferior fat pad of the knee. Such fat pad injury could be partially responsible for the apparent post-injury pro-inflammatory response noted in ACL-injured individuals. However, future longitudinal studies are needed to link ACL-rupture associated fat pad injury with important patient outcomes such as the development of posttraumatic osteoarthritis.

Less Severe Preoperative Synovitis is Associated With Higher Self-reported Pain Intensity 12 Months After Total Knee Arthroplasty-An Exploratory Prospective Observational Study

OBJECTIVES

Synovitis is one of the possible pain generators in osteoarthritis (OA) and is associated with upregulation of proinflammatory cytokines, which can lead to worsening of the postoperative pain. This exploratory study aimed to investigate the association between perioperative synovitis and self-reported pain 12 months after total knee arthroplasty (TKA) in patients with OA.

MATERIALS AND METHODS

Twenty-six knee OA patients were included in this analysis. The perioperative volume of synovitis in predefined locations was assessed by contrast-enhanced magnetic resonance imaging (CE-MRI) and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Perioperative synovitis was assessed histologically from biopsies of the synovium. Highest pain intensity within the last 24 hours (Visual Analog Scale, VAS, 0 to 100) was assessed before and 12 months after TKA. Patients were divided into a low-pain intensity (VAS≤30) and a high-pain intensity (VAS>30) group on the basis of 12 months postoperative VAS.

RESULTS

The high-pain intensity group had significantly lower perioperative contrast-enhanced-synovitis (P=0.025), DCE-synovitis (P<0.04), and a trend toward lower histologically assessed synovitis (P=0.077) compared with the low-pain intensity group. Perioperative synovitis scores were inversely correlated with pain intensity 12 months after TKA (P<0.05), indicating that more severe perioperative synovitis is associated with less severe pain intensity at 12 months.

DISCUSSION

Higher degrees of perioperative synovitis scores are found to be associated with less postoperative pain 12 months after TKA. Further, correlation analysis revealed that less severe perioperative CE-MRI and DCE-MRI synovitis was associated with higher pain intensity 12 months after TKA, suggesting that CE-MRI and DCE-MRI synovitis grades could be used as imaging markers for prediction of chronic postoperative pain after TKA.

The COX-2 inhibitor etoricoxib reduces experimental osteoarthritis and nociception in rats: The roles of TGF-β1 and NGF expressions in chondrocytes

BACKGROUND

Osteoarthritis (OA) is the most common joint disease, especially affecting the knee joint. Etoricoxib, a highly selective cyclooxygenase (COX)-2 inhibitor which can reduce postoperative pain after orthopaedic surgery. The aim of this study was to investigate the effects of oral etoricoxib on the development of OA and to examine concomitant changes in the nociceptive behaviour of rats.

METHOD

OA was induced in wistar rats by anterior cruciate ligament transection (ACLT) of the right knee. The ACLT + etoricoxib groups received 6.7 or 33.3 mg/kg of oral etoricoxib three times a week for 12 consecutive weeks, starting at week 8 after ACLT. Nociceptive behaviours and changes in knee joint width during OA development were analyzed. Histopathological studies were then performed on the cartilage. Immunohistochemical analysis was performed to examine the effect of etoricoxib on the expression of transforming growth factor-beta (TGF-β) and nerve growth factor (NGF) in articular cartilage chondrocytes.

RESULTS

OA rats receiving etoricoxib showed a significantly lower degree of cartilage degeneration than the rats receiving placebo. Nociceptive behaviour studies showed significant improvement in the ACLT + etoricoxib groups compared to that in the ACLT group. Moreover, etoricoxib attenuated NGF expression, but increased TGF-β expression, in OA-affected cartilage.

CONCLUSIONS

Oral etoricoxib in a rat OA model (a) attenuates the development of OA, (b) concomitantly reduces nociception, and (c) modulates chondrocyte metabolism, possibly by inhibiting NGF expression and increasing TGF-β expression.

SIGNIFICANCE

Oral administration of etoricoxib can attenuate the development of OA, with an associated attenuation of nociceptive behaviour in an experimental rat OA model. Moreover, etoricoxib attenuated NGF expression, but enhanced TGF-β expression in OA-affected chondrocytes. These findings may pave the way for further investigations of etoricoxib as a potential therapeutic target for the treatment of the inflammatory component in OA.

Multiple Platelet-Rich Plasma Injections Versus Single Platelet-Rich Plasma Injection in Early Osteoarthritis of the Knee: An Experimental Study in a Guinea Pig Model of Early Knee Osteoarthritis

BACKGROUND

Platelet-rich plasma (PRP) has emerged as the forerunner among disease-modifying treatment options for early osteoarthritis (OA) of the knee. However, no consensus is available regarding optimum dosing schedules.

PURPOSE

To determine whether multiple injections of PRP (3 injections) provide better short-term and long-term results than a single injection of PRP in a guinea pig model of knee OA.

STUDY DESIGN

Controlled laboratory study.

METHODS

36 Dunkin-Hartley guinea pigs (weighing ~600-800 g) were chosen for this study. The animals were assigned to group DC (disease control group), group G1 (single-PRP group), and group G2 (multiple-PRP group) containing 10, 10, and 12 animals, respectively. Another 4 animals were used for preparation of allogenic PRP. Groups G1 and G2 received 1 and 3 injections of PRP, respectively, at weekly intervals in the intervention knee while the contralateral knee was injected with normal saline. Group DC received no intervention in either knee. Half of the animals from each group (subgroups DC.3, G1.3, and G2.3) were sacrificed at 3 months, and the remaining half (subgroups DC.6, G1.6, and G2.6) were sacrificed at 6 months after intervention. Both knee joints were harvested for histological assessment of articular cartilage and synovium.

RESULTS

The mean synovial scores for groups G1 and G2 were significantly better than those for group DC at 3 months. No difference was found between groups G1 and G2 at 3 months. At 6 months, group G2 had significantly better mean synovial scores than group G1 and group DC. The mean articular cartilage scores in group G2 were significantly better than those in group DC at 3 months. However, at 6 months, no significant difference was found among any of the groups in terms of mean articular scores.

CONCLUSION

Both single and multiple injections of PRP exert similar anti-inflammatory effects on the synovium in the short term. However, this effect is sustained in the long term only for multiple injections. Multiple injections of PRP exert a chondroprotective effect, but only in the short term. This effect is not seen with a single injection of PRP.

CLINICAL RELEVANCE

This study provides insight into the histological basis for the superiority of multiple injections of PRP.

Synovitis as a concomitant disease in shoulder pathologies

INTRODUCTION

Shoulder pathologies are often accompanied by rotator interval synovitis. This phenomenon is poorly described in the literature so far. The aim of the study was to analyze the occurrence of macroscopically visible synovial reaction in the rotator interval in patients with chronic shoulder pathologies and to perform a histopathological evaluation.

MATERIALS AND METHODS

In this prospective cohort study, 167 consecutive patients undergoing arthroscopic shoulder surgery for chronic shoulder pathology were included (♀ = 45, ♂ = 122; [Formula: see text]54.5 years ± 12.8). Included patients were divided into subgroups according to the encountered chronic shoulder pathology: (1) impingement syndrome with or without bursal sided partial rotator cuff tear (RCT); (2) articular sided partial RCT; (3) full-thickness RCT; (4) RCT that involves at least two tendons; (5) shoulder instability; and (6) cartilage damage. Standardized soft tissue biopsies from the rotator interval were taken. The synovitis score of Krenn/Morawietz was used for histopathological examination.

RESULTS

Extraarticular pathology (group 1) showed significantly decreased synovitis scores compared to all the other groups. Increased size of rotator cuff tears (group 4), as well as cartilage damage (group 6) showed significantly higher synovitis scores than group 3 (p < 0.05). Moreover, the synovitis score was significantly increased in patients with concomitant pathologies of the long head of the biceps (p = 0.001).

CONCLUSIONS

This study suggests that chronic intra- and extraarticular shoulder diseases are very often accompanied by a histopathologically verifiable low-grade synovitis. Intraarticular pathologies seem to induce increased levels of synovitis. Furthermore, the increased size of rotator cuff tears is accompanied by a higher degree of synovitis.

STUDY DESIGN

Cohort study, level of evidence, 2b.

Exploring longitudinal associations of histologically assessed inflammation with symptoms and radiographic damage in knee osteoarthritis: combined results of three prospective cohort studies

OBJECTIVE

To explore the associations between different histologically assessed, inflammatory synovial characteristics and subsequent clinical and structural aspects in knee osteoarthritis (OA).

DESIGN

Knee OA patients, ranging in stage from early to advanced, were recruited from three different ongoing studies. Synovial tissue biopsies were taken and histologically assessed for six features (four inflammatory related aspects, fibrosis and fibrin deposition). Clinical aspects (WOMAC pain, functioning and stiffness and SF-36 vitality) and structural aspects (Kellgren and Lawrence (KL)-grade, joint space narrowing (JSN; 0-3) and osteophytes (0-3), and reception of total knee replacement (TKR)) were repeatedly assessed during follow-up. Associations between histology and clinical and structural aspects were analysed using linear mixed model analyses and cox proportional hazards analysis.

RESULTS

Biopsies of 83 patients (median complaint duration: 5 [2-8] years) were analysed. Follow-up was a median of 1.4 [0.8-2.7] years for clinical and 1.8 [0.2-5.2] years for structural aspects. Fibrosis and fibrin deposition were inversely correlated with the inflammatory features. A higher fibrosis score was associated with a lower scores for KL-grade, JSN and osteophytes, while higher scores for perivascular oedema, synovial lining thickness and vascularisation were associated with higher scores for structural aspects during follow-up. No associations were found between each of the histological features and any of the clinical aspects or the chance for TKR during follow-up.

CONCLUSIONS

Inflammatory related histological aspects are associated with subsequent increased radiological severity in knee OA, while fibrosis seems to protect against this, providing a potential therapeutic target for OA treatment.

Signal intensity alteration within infrapatellar fat pad predicts knee replacement within 5 years: data from the Osteoarthritis Initiative

OBJECTIVE

To investigate whether infrapatellar fat pad (IPFP) signal intensity (SI) alteration predicts the occurrence of knee replacement (KR) in knee osteoarthritis (OA) patients over 5 years.

DESIGN

The subjects were selected from Osteoarthritis Initiative (OAI) study. Case knees (n = 127) were defined as those who received KR during 5 years follow-up visit. They were matched by gender, age and radiographic status with control knees (n = 127). We used T2-weighted MR images to measure IPFP SI alteration using a newly developed algorithm in MATLAB. The measurements were assessed at baseline (BL), T0 (the visit just before KR) and 1 year before T0 (T-1). Conditional logistic regression was used to analyse the associations between IPFP SI alterations and the risk of KR.

RESULTS

Participants were mostly female (57%), with an average age of 63.7 years old and a mean body mass index (BMI) of 29.5 kg/m². In multivariable analysis, the standard deviation (SD) of IPFP SI [sDev (IPFP)] and the ratio of high SI region volume to whole IPFP volume [Percentage (H)] measured at BL were significantly associated with increased risks of KR after adjustment for covariates. IPFP SI alterations measured at T-1 including sDev (IPFP), Percentage (H) and clustering effect of high SI [Clustering factor (H)] were significantly associated with higher risks of KR. All measurements were significantly associated with higher risks of KR at T0.

CONCLUSIONS

IPFP SI is associated with the occurrence of KR suggesting it may play a role in end-stage knee OA.

Knee joint synovitis: study of correlations and diagnostic performances of ultrasonography compared with histopathology

Objectives

Ultrasonography (US) is a fast, available and low-cost imaging tool used for detecting knee synovitis. Our aims were to assess the relationship between US and histology findings in appraising levels of inflammation and vascularity in the knee joint in subjects with inflammatory arthropathies; to determine whether differences exist in the appraisal between varying knee compartments and to compare US performances compared with gold standard histology for knee synovitis detection.

Methods

Subjects with actively inflamed knee joint having crystal arthropathies, rheumatoid arthritis, psoriatic arthritis or ostoearthritis were prospectively recruited from rheumatology clinics after giving their written consent between May and October 2015. Study was approved by the institutional ethics committee. The knee was divided into three compartments (medial, lateral, superior). Patients had a knee US followed by a knee arthroscopy with biopsies retrieval from each compartment. Biopsies were blindly scored for lining layer hyperplasia, inflammation, vascularity, CD68 and factor VIII staining. Correlation was determined using the Spearman’s correlation test.

Results

26 patients with active arthritis in a knee joint and recent onset of disease were prospectively included. Strong correlations were observed between US synovitis grade and histological inflammation score (r=0.63; P=0.002), US Doppler grade and histological score for vascularity (r=0.68; P<0.001); US measured synovial thickness and lining layer hyperplasia (r=0.61; P=0.002). Moderate correlation was found between US synovitis grade and CD68 score (r=0.49; P=0.02).

Conclusion

US findings correlate with histological inflammation and vascularity scores in actively inflamed knee joints. US accurately describes knee synovitis.

Increased bone tracer uptake in symptomatic patients with ACL graft insufficiency: a correlation of MRI and SPECT/CT findings

PURPOSE

Magnetic resonance imaging (MRI) and single-photon emission computerised tomography/computerised tomography (SPECT/CT) are used as diagnostic tools in symptomatic patients after reconstruction of the anterior cruciate ligament (ACL). The benefit of SPECT/CT in comparison with MRI is under debate. The purpose of this study was to investigate whether and how bone tracer uptake (BTU) intensity and distribution in SPECT/CT correlate with MRI findings in symptomatic patients after ACL reconstruction.

METHODS

Twenty-nine patients (male:female = 22:7, mean age ± SD 26 ± 10 years) with symptoms of pain and instability after ACL reconstruction were retrospectively investigated using prospectively acquired SPECT/CT and MRI. On MRI graft tear, graft signal intensity, bone marrow oedema, tunnel cyst formation, roof impingement, roof osteophytes, local arthrofibrosis, joint effusion and synovial thickness were analysed by two readers blinded to the BTU results. BTU was anatomically localised and volumetrically quantified. Spearman's rho test was used for correlation of BTU in SPECT/CT and MRI findings (p < 0.05).

RESULTS

SPECT/CT showed increased femoral and tibial BTU in patients with MRI-confirmed graft tear, signal hyperintensity of the intraarticular graft section, joint effusion, synovial thickening, roof osteophytes and bone marrow oedema. Cyst formation in the femoral tunnel results in significantly reduced BTU in femur and tibia. No correlation of increased BTU was found for graft impingement and graft arthrofibrosis.

CONCLUSIONS

Bone tracer uptake in SPECT/CT and defined MRI findings in symptomatic patients after ACL reconstruction were correlated. Both imaging modalities have a definite role in post-operative diagnostic and have established their value in those patients. This study provides a better understanding of the clinical value of SPECT/CT versus MRI in the clinical decision-making process. SPECT/CT provides a window into the in vivo loading of the joint as well as bone remodelling and graft incorporation process. In addition, ACL graft insufficiency can be detected by increased BTU.

LEVEL OF EVIDENCE

Retrospective cohort study, Level III.

The effect of intra-articular allogenic platelet rich plasma in Dunkin-Hartley guinea pig model of knee osteoarthritis

Objectives

To investigate the pathway for disease modifying effect of the PRP in osteoarthritis of knee.

Design

Two experimental models (group I and II) of Twelve Dunkin-Hartley guinea pigs each were enrolled as a part of a prospective controlled experimental study. One knee was enrolled for intervention and the other knee of the same animal used as control, the intervention being three intra-articular allogenic PRP injections given at a weekly interval. Equal volume of isotonic saline injection were given simultaneously in the control knees. Six animals from each model (subgroup IA, IIA) were euthanized at three months and the remaining six (subgroup IB, IIB) at six months post intervention. Samples of synovial fluid were collected from each knee joint for COMP level analysis by ELISA and bilateral knee joints were harvested for histopathological assessment of articular cartilage and synovium at the time of euthanasia.

Results

Mean synovial fluid COMP concentration was significantly lower in PRP treated knees (p<0.05) at three months. On histological examination mean synovitis scores and synovial vascularity were significantly lower in PRP treated knees as compared to controls at both three and six months (p < 0.05). Additionally mean articular cartilage degeneration was significantly lower in PRP treated knees in group 1 only (p<0.05).

Conclusion

Our preliminary data from the study has shown some evidence of positive influence of PRP in knee OA, possibly due to its anti-inflammatory effect and disease modifying effect, shown by short-term chondro-protective effect in PRP injected knees.

Level of evidence

V.

Is arthroscopic videotape a reliable tool for describing early joint tissue pathology of the knee?

BACKGROUND

The aim of this study was to assess the reliability of the videotape scoring system collected during knee arthroscopy for meniscal tears, and to test the consistency with intra-operative findings.

METHODS

Fifty-seven patients undergoing arthroscopic treatment of meniscal tears were included in the analysis. The cartilage damage was assessed intra-operatively, at six sites, using the Outerbridge scoring system. The meniscal tears were graded according to the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) classification. The presence of synovial inflammation was scored, at four different sites, according to the macro-score method. The total cartilage, meniscal and synovial scores were calculated for each knee by the sum of the maximum grade of the lesions at each anatomic site. In order to assess the reliability of the arthroscopic scoring system, the videotapes recorded during the arthroscopy were reviewed by two independent observers one year after the surgery and compared with the scores completed by the surgeon during the operation.

RESULTS

The total cartilage score showed substantial inter-rater and intra-rater reliability, and moderate consistency with the intra-operative score provided by the surgeon. The total meniscal score showed substantial inter-rater and intra-rater reliability, and good consistency with the intra-operative findings. The total synovial score showed substantial inter-rater agreement, substantial intra-rater reliability, and moderate consistency with intra-operative findings.

CONCLUSIONS

The videotape scoring system provided a reliable and reproducible system for recording the intra-operative state of the whole joint pathology in patients undergoing arthroscopic treatment of meniscal tears.

Acromegalic arthropathy in various stages of the disease: an MRI study

BACKGROUND

Arthropathy is a prevalent and invalidating complication of acromegaly with a characteristic radiographic phenotype. We aimed to further characterize cartilage and bone abnormalities associated with acromegalic arthropathy using magnetic resonance imaging (MRI).

METHODS

Twenty-six patients (23% women, mean age 56.8 ± 13.4 years), with active (n = 10) and controlled acromegaly (n = 16) underwent a 3.0 T MRI of the right knee. Osteophytes, cartilage defects, bone marrow lesions and subchondral cysts were assessed by the Knee Osteoarthritis Scoring System (KOSS) method. Cartilage thickness and cartilage T2 relaxation times, in which higher values reflect increased water content and/or structural changes, were measured. Twenty-five controls (52% women, mean age: 59.6 ± 8.0 years) with primary knee OA were included for comparison.

RESULTS

Both in active and controlled acromegaly, structural OA defects were highly prevalent, with thickest cartilage and highest cartilage T2 relaxation times in the active patients. When compared to primary OA subjects, patients with acromegaly seem to have less cysts (12% vs 48%, P = 0.001) and bone marrow lesions (15% vs 80%, P = 0.006), but comparable prevalence of osteophytosis and cartilage defects. Patients with acromegaly had 31% thicker total joint cartilage (P < 0.001) with higher cartilage T2 relaxation times at all measured sites than primary OA subjects (P < 0.01).

CONCLUSIONS

Patients with active acromegaly have a high prevalence of structural OA abnormalities in combination with thick joint cartilage. In addition, T2 relaxation times of cartilage are high in active patients, indicating unhealthy cartilage with increased water content, which is (partially) reversible by adequate treatment. Patients with acromegaly have a different distribution of structural OA abnormalities visualized by MRI than primary OA subjects, especially of cartilage defects.

EULAR recommendations for the use of imaging in the clinical management of peripheral joint osteoarthritis

The increased information provided by modern imaging has led to its more extensive use. Our aim was to develop evidence-based recommendations for the use of imaging in the clinical management of the most common arthropathy, osteoarthritis (OA). A task force (including rheumatologists, radiologists, methodologists, primary care doctors and patients) from nine countries defined 10 questions on the role of imaging in OA to support a systematic literature review (SLR). Joints of interest were the knee, hip, hand and foot; imaging modalities included conventional radiography (CR), MRI, ultrasonography, CT and nuclear medicine. PubMed and EMBASE were searched. The evidence was presented to the task force who subsequently developed the recommendations. The strength of agreement for each recommendation was assessed. 17 011 references were identified from which 390 studies were included in the SLR. Seven recommendations were produced, covering the lack of need for diagnostic imaging in patients with typical symptoms; the role of imaging in differential diagnosis; the lack of benefit in monitoring when no therapeutic modification is related, though consideration is required when unexpected clinical deterioration occurs; CR as the first-choice imaging modality; consideration of how to correctly acquire images and the role of imaging in guiding local injections. Recommendations for future research were also developed based on gaps in evidence, such as the use of imaging in identifying therapeutic targets, and demonstrating the added value of imaging. These evidence-based recommendations and related research agenda provide the basis for sensible use of imaging in routine clinical assessment of people with OA.

Synovitis in osteoarthritis: current understanding with therapeutic implications

Modern concepts of osteoarthritis (OA) have been forever changed by modern imaging phenotypes demonstrating complex and multi-tissue pathologies involving cartilage, subchondral bone and (increasingly recognized) inflammation of the synovium. The synovium may show significant changes, even before visible cartilage degeneration has occurred, with infiltration of mononuclear cells, thickening of the synovial lining layer and production of inflammatory cytokines. The combination of sensitive imaging modalities and tissue examination has confirmed a high prevalence of synovial inflammation in all stages of OA, with a number of studies demonstrating that synovitis is related to pain, poor function and may even be an independent driver of radiographic OA onset and structural progression. Treating key aspects of synovial inflammation therefore holds great promise for analgesia and also for structure modification. This article will review current knowledge on the prevalence of synovitis in OA and its role in symptoms and structural progression, and explore lessons learnt from targeting synovitis therapeutically.

The association between histological, macroscopic and magnetic resonance imaging assessed synovitis in end-stage knee osteoarthritis: a cross-sectional study

OBJECTIVES

To investigate the association between magnetic resonance imaging (MRI), macroscopic and histological assessments of synovitis in end-stage knee osteoarthritis (KOA).

METHODS

Synovitis of end-stage osteoarthritic knees was assessed using non-contrast-enhanced (CE), contrast-enhanced magnetic resonance imaging (CE-MRI) and dynamic contrast-enhanced (DCE)-MRI prior to (TKR) and correlated with microscopic and macroscopic assessments of synovitis obtained intraoperatively. Multiple bivariate correlations were used with a pre-specified threshold of 0.70 for significance. Also, multiple regression analyses with different subsets of MRI-variables as explanatory variables and the histology score as outcome variable were performed with the intention to find MRI-variables that best explain the variance in histological synovitis (i.e., highest R²). A stepped approach was taken starting with basic characteristics and non-CE MRI-variables (model 1), after which CE-MRI-variables were added (model 2) with the final model also including DCE-MRI-variables (model 3).

RESULTS

39 patients (56.4% women, mean age 68 years, Kellgren-Lawrence (KL) grade 4) had complete MRI and histological data. Only the DCE-MRI variable MExNvoxel (surrogate of the volume and degree of synovitis) and the macroscopic score showed correlations above the pre-specified threshold for acceptance with histological inflammation. The maximum R²-value obtained in Model 1 was R² = 0.39. In Model 2, where the CE-MRI-variables were added, the highest R² = 0.52. In Model 3, a four-variable model consisting of the gender, one CE-MRI and two DCE-MRI-variables yielded a R² = 0.71.

CONCLUSION

DCE-MRI is correlated with histological synovitis in end-stage KOA and the combination of CE and DCE-MRI may be a useful, non-invasive tool in characterising synovitis in KOA.

Evolution of synovitis in osteoarthritic knees and its association with clinical features

OBJECTIVE

To investigate the course of synovitis on contrast-enhanced magnetic resonance images (CE-MRI) in osteoarthritic knees over 2 years, and its association with pain and cartilage deterioration.

DESIGN

Consecutive patients (n = 39, mean age 61 years, 79% woman, median (range) body mass index (BMI) 29 (24-48) kg/mm²) with clinical osteoarthritis (OA) were included. Baseline and follow-up CE-MRI (3 T) were scored paired in chronological order for synovitis (semi-quantitatively at 11 sites (range 0-22)), cartilage deterioration and bone marrow lesions (BMLs) (semi-quantitatively according to Knee Osteoarthritis Scoring System (KOSS)). Changes in sum scores were calculated. Cartilage deterioration was defined as change of ≥2 above the smallest detectable change (SDC). Pain was assessed by standardized questionnaires. Analysis of covariance (ANCOVA) and linear regression models were used to investigate association between synovitis change and cartilage deterioration and between synovitis change or cartilage deterioration and change in pain.

RESULTS

The total synovitis score did not change over 2 years (mean change 0.2 (standard deviation (SD) 3.2)), although changes in individual patients were observed. Cartilage deterioration was observed in 51% of patients. Synovitis change score was lower in patients without compared to patients with cartilage deterioration, taking BML change in account (mean difference -2.1 (-4.1 to -0.1)). Change in synovitis was not associated with change in pain, whereas cartilage deterioration was associated with change in Intermittent and Constant OsteoArthritis Pain (ICOAP) constant pain in adjusted models (unstandardised coefficient (B) (95% confidence interval (CI)) 2.8 (0.4-5.3)).

CONCLUSIONS

In individual patients synovitis fluctuates during disease course. Synovitis change was not associated with change in pain. Increase in synovitis is associated with cartilage deterioration, suggesting a role for synovitis as a target for disease-modifying treatment.

Characterization of synovial mast cells in knee osteoarthritis: association with clinical parameters

OBJECTIVE

To investigate the presence of mast cells in the osteoarthritic (OA) synovium and their association with clinical parameters in comparison with rheumatoid arthritis (RA) samples.

METHOD

Synovial tissues of 56 symptomatic OA and 49 RA patients were obtained. Two to three paraffin slides were used to quantify inflammation using haematoxylin and eosin (H&E) staining (synovitis score 0-9), and numbers of mast cells (per 10 high-power fields) using double immunofluorescence for CD117 and tryptase. Average scores per patient were used for analysis. Knee radiographs of OA patients were scored according to the Kellgren and Lawrence (KL) system and pain was determined in OA patients at baseline by visual analogue scale (VAS).

RESULTS

Median (range) of mast cells was significantly higher in OA samples 45 (1-168) compared to RA samples 4 (1-47) (P-value < 0.001), despite a lower median (range) synovitis score in OA (2.5 (0-6.0)) compared to 4.6 (0-8.0) in RA samples. The synovitis score was significantly correlated with the number of mast cells (in OA Spearman's rho (P-value) 0.3 (0.023) and RA 0.5 (P-value < 0.001)). Interestingly, we observed a trend towards an association between the number of mast cells and an increased KL-grade (P-value 0.05) in OA patients, independently of synovitis. No associations were found with self-reported pain.

CONCLUSION

Prevalence of mast cells in OA synovial tissue is relatively high and associates with structural damage in OA patients, suggesting a role of mast cells in this disease.

Inflammatory Cells in Patients with Endstage Knee Osteoarthritis: A Comparison between the Synovium and the Infrapatellar Fat Pad

OBJECTIVE

To get a better understanding of inflammatory pathways active in the osteoarthritic (OA) joint, we characterized and compared inflammatory cells in the synovium and the infrapatellar fat pad (IFP) of patients with knee OA.

METHODS

Infiltrating immune cells were characterized by flow cytometry in 76 patients with knee OA (mean age 63.3, 52% women, median body mass index 28.9) from whom synovial tissue (n = 40) and IFP (n = 68) samples were obtained. Pain was assessed by the visual analog scale (VAS; 0-100 mm). Spearman rank correlations and linear regression analyses adjusted for sex and age were performed.

RESULTS

Macrophages and T cells, followed by mast cells, were the most predominant immune cells in the synovium and IFP, and were equally abundant in these tissues. Macrophages and T cells secreted mostly proinflammatory cytokines even without additional stimulation, indicating their activated state. Accordingly, most CD4+ T cells had a memory phenotype and contained a significant population of cells expressing activation markers (CD25+, CD69+). Interestingly, the percent of CD69+ T cells was higher in synovial than IFP CD4+ T cells. Preliminary analyses indicated that the number of synovial CD4+ T cells were associated with VAS pain (β 0.51, 95% CI 0.09-1.02, p = 0.02).

CONCLUSION

Our data suggest that the immune cell composition of the synovium and the IFP is similar, and includes activated cells that could contribute to inflammation through secretion of proinflammatory cytokines. Moreover, preliminary analyses indicate that synovial CD4+ T cells might associate with pain in patients with endstage OA of the knee.

Cross-sectional and Longitudinal Associations between Knee Joint Effusion Synovitis and Knee Pain in Older Adults

OBJECTIVE

To describe the cross-sectional and longitudinal associations between knee regional effusion synovitis and knee pain in older adults.

METHODS

Data from a population-based random sample (n = 880, mean age 62 yrs, 50% women) were used. Baseline knee joint effusion synovitis was graded (0-3) using T2-weighted magnetic resonance imaging (MRI) in the suprapatellar pouch, central portion, posterior femoral recess, and subpopliteal recess. Effusion synovitis of the whole joint was defined as a score of ≥ 2 in any subregion. Other knee structural (including cartilage, bone marrow, and menisci) lesions were assessed by MRI at baseline. Knee pain was assessed by the Western Ontario and McMaster Universities Osteoarthritis Index questionnaire at baseline and 2.6 years later. Multivariable analyses were performed after adjustment for age, sex, body mass index, and other structural lesions.

RESULTS

The prevalence of effusion synovitis was 67%. Suprapatellar pouch effusion synovitis was significantly and independently associated with increased total and nonweight-bearing knee pain in both cross-sectional and longitudinal analyses (for an increase in total knee pain of ≥ 5, RR 1.26 per grade, 95% CI 1.04-1.52), and increased weight-bearing knee pain in longitudinal analysis only. Effusion synovitis in posterior femoral recess and central portion were independently associated with increases in nonweight-bearing pain (RR 1.63 per grade, 95% CI 1.32-2.01 and RR 1.29 per grade, 95% CI 1.01-1.65, respectively) in longitudinal analyses only.

CONCLUSION

Knee joint effusion synovitis has independent associations with knee pain in older adults. Suprapatellar pouch effusion synovitis is associated with nonweight-bearing and weight-bearing knee pain, while posterior femoral recess and central portion effusion synovitis are only associated with nonweight-bearing pain.

Bone marrow lesions, subchondral bone cysts and subchondral bone attrition are associated with histological synovitis in patients with end-stage knee osteoarthritis: a cross-sectional study

OBJECTIVE

The aim of this study was to examine the osteoarthritis (OA)-related structural changes associated with histological synovitis in end-stage knee OA patients.

METHODS

Forty end-stage knee OA patients (female: 88%, mean age: 71.8 y) were enrolled. All participants underwent 3.0-T MRI. The structural changes, such as cartilage morphology, subchondral bone marrow lesion (BML), subchondral bone cyst (SBC), subchondral bone attrition (SBA), osteophytes, meniscal lesion and synovitis, were scored using the whole-organ MRI scoring (WORMS) method. Synovial samples were obtained from five regions of interest (ROIs) of the knee joint during total joint replacement surgery. The associations between the histological synovitis score (HSS) and WORMS or the synovial expression levels of cyclooxygenase (COX)-2, interleukin (IL)-1β, IL-6 and transforming growth factor (TGF)-β were examined using Spearman's correlation coefficient.

RESULTS

Among the seven OA-related structural changes, the BML, SBC, SBA and synovitis were significantly associated with the HSS (r = 0.33, 0.35, 0.48 and 0.36, respectively), while other morphological changes were not. Although synovial COX-2, IL-1β or IL-6 expression levels were not associated with the HSS, the synovial TGF-β expression levels were associated with the HSS.

CONCLUSION

The presence of BML, SBC and SBA was associated with histological synovitis in end-stage knee OA patients.

Inflammation (or synovitis)-driven osteoarthritis: an opportunity for personalizing prognosis and treatment?

The disabling and painful disease osteoarthritis (OA) is the most common form of arthritis. Strong evidence suggests that a subpopulation of OA patients has a form of OA driven by inflammation. Consequently, understanding when inflammation is the driver of disease progression and which OA patients might benefit from anti-inflammatory treatment is a topic of intense research in the OA field. We have reviewed the current literature on OA, with an emphasis on inflammation in OA, biochemical markers of structural damage, and anti-inflammatory treatments for OA. The literature suggests that the OA patient population is diverse, consisting of several subpopulations, including one associated with inflammation. This inflammatory subpopulation may be identified by a combination of novel serological inflammatory biomarkers. Preliminary evidence from small clinical studies suggests that this subpopulation may benefit from anti-inflammatory treatment currently reserved for other inflammatory arthritides.

A Systematic Review Investigating the Presence of Inflammatory Synovitis in Hip and Knee Joint Replacement Surgery

Synovial tissue can display an inflammatory response in the presence of OA. There is increasing interest to better understand the role of inflammation in OA, particularly with regard to those who require joint replacement. A systematic review of inflammatory synovitis in OA of literature databases was undertaken from their inception until October 14, 2014. Independent critical appraisal of each study was undertaken using the CASP appraisal tool. From a total of sixty-six identified citations, twenty-three studies were deemed eligible for review. The studies presented moderate to strong methodological quality. Strong correlation was identified between histological and imaging synovitis severity. Correlation was weaker between clinical symptoms and imaging and/or histological synovitis severity. There was little consensus, with regard to expressed cytokines and chemokines at the different stages of OA disease progression. Few studies investigated the influence of inflammatory synovitis on the outcome of major joint replacement. Research into inflammatory synovitis in OA is an emerging field. Longitudinal studies applying proven imaging modalities, histological analysis, and longer follow-up are required in order to further define our understanding of the role of synovitis in the pathogenesis of OA and its effects on outcomes following major joint replacement.

Macroscopic and microscopic assessments of the glenohumeral and subacromial synovitis in rotator cuff disease

Background

Whereas synovitis is one of most common findings during arthroscopic surgery in patients with rotator cuff diseases, no study has investigated its characteristics. We propose a macroscopic assessment system for investigating the characteristics of synovitis.

Methods

Fifty-four patients with a full-thickness rotator cuff tear undergoing arthroscopic rotator cuff repair with an average age of 62.5 ± 7.0 years were included. For the macroscopic assessment, 3 parameters, villous hypertrophy, hyperemia, and density, were measured and translated into grades in 3 regions-of-interest (ROI) in the glenohumeral joint and 4 ROIs in the subacromial space. For the microscopic assessments, 4 commonly used microscopic assessment systems were used. The reliability and association between the macroscopic and microscopic assessments were investigated.

Results

The inter- and intra-observer reliability of all of the macroscopic and microscopic assessments were excellent. The severity of synovitis was significantly greater in the glenohumeral joint than that in the subacromial space, 1.54 ± 0.61 versus 0.94 ± 0.56 (p < 0.001). Synovitis varied with respect to location, and was generally more severe near the tear with the macroscopic assessment system. Meanwhile, none of the microscopic assessment systems demonstrated differences between different ROIs in both the glenohumeral joint and the subacromial space.

Conclusions

The macroscopic assessment system for synovitis in rotator cuff disease in this study showed excellent reliability. It critically described characteristics of synovitis that microscopic assessment systems could not. Therefore, this system could be a useful tool for investigating synovitis in rotator cuff disease.

Association of pain in knee osteoarthritis with distinct patterns of synovitis

OBJECTIVE

To determine possible patterns of synovitis on contrast-enhanced magnetic resonance imaging (CE-MRI) and its relation to pain and severity in patients with radiographic knee osteoarthritis (OA).

METHODS

In total, 86 patients (mean age 62 years, 66% women, median body mass index 29 kg/m(2) ) with symptomatic knee OA (Kellgren/Lawrence radiographic score 3) were included. T1-weighted, gadolinium-chelate-enhanced MRI with fat suppression was used to semiquantitatively score the extent of synovitis at 11 knee sites (total score range 0-22). Self-reported pain was assessed with 3 standardized questionnaires. Principal components analysis (PCA) was used to investigate patterns (the location and severity) of synovitis. Subsequently, these patterns were assessed for associations with pain measures and radiographic severity in adjusted logistic regression models.

RESULTS

Synovitis was observed in 86 patients and was found to be generally mild on CE-MRI (median total synovitis score 7, range 0-16). The median pain scores were 53 (range 0-96) on the visual analog scale for pain, 51.4 (range 2.8-97.2) on the Knee Injury and Osteoarthritis Outcome Score (KOOS) for pain, 35 (range 0-75) on the Intermittent and Constant Osteoarthritis Pain (ICOAP) score for constant pain, and 40.6 (range 0-87.5) on the ICOAP score for intermittent pain. PCA resulted in extraction of 3 components, explaining 53.4% of the variance. Component 1 was characterized by synovitis at 7 sites (mainly medial parapatellar involvement) and was associated with scores on the KOOS pain subscale and the ICOAP constant pain subscale. Component 2 was characterized by synovitis at 4 sites (mainly the site adjacent to the anterior cruciate ligament), but was not associated with pain measures or with radiographic severity. Component 3, characterized by synovitis at 3 sites (mainly at the loose body site), was associated with radiographic severity.

CONCLUSION

Different patterns of synovitis in knee OA were observed. The pattern that included several patellar sites was associated with pain, whereas other patterns showed no association, suggesting that pain perception in patients with knee OA is a localized response.

Emerging regulators of the inflammatory process in osteoarthritis

Chronic, low-grade inflammation in osteoarthritis (OA) contributes to symptoms and disease progression. Effective disease-modifying OA therapies are lacking, but better understanding inflammatory pathophysiology in OA could lead to transformative therapy. Networks of diverse innate inflammatory danger signals, including complement and alarmins, are activated in OA. Through inflammatory mediators, biomechanical injury and oxidative stress compromise the viability of chondrocytes, reprogramming them to hypertrophic differentiation and proinflammatory and pro-catabolic responses. Integral to this reprogramming are 'switching' pathways in transcriptional networks, other than the well-characterized effects of NFκB and mitogen-activated protein kinase signalling; HIF-2α transcriptional signalling and ZIP8-mediated Zn(2+) uptake, with downstream MTF1 transcriptional signalling, have been implicated but further validation is required. Permissive factors, including impaired bioenergetics via altered mitochondrial function and decreased activity of bioenergy sensors, interact with molecular inflammatory responses and proteostasis mechanisms such as the unfolded protein response and autophagy. Bioenergy-sensing by AMPK and SIRT1 provides 'stop signals' for oxidative stress, inflammatory, and matrix catabolic processes in chondrocytes. The complexity of molecular inflammatory processes in OA and the involvement of multiple inflammatory mediators in tissue repair responses, raises daunting questions about how to therapeutically target inflammatory processes and macroscopic inflammation in OA. Bioenergy sensing might provide a pragmatic 'entry point'.