Morphology of the sternoclavicular joint and its microanatomical changes in response to osteoarthritic degeneration

Although the sternoclavicular joint shares structural similarities with the knee and hip joints as a diarthrodial joint, its biomechanics differ significantly due to its non-weight-bearing nature. Nevertheless, it is subject to considerable loading, leading to increased susceptibility to osteoarthritis, a prevalent condition characterized by the degeneration of the joint's articular surfaces and fibrocartilaginous intra-articular disc. The osteoarthritic degeneration of the fibrocartilaginous and cartilaginous surfaces of the sternoclavicular joint has been investigated, considering multiple factors. These include cell count, collagen alignment, surface fibrillation, cyst formation, and glycosaminoglycan content, with the findings deemed significant. However, current treatments for osteoarthritis of the sternoclavicular joint tend to focus on symptom management rather than active prevention of disease progression. Therefore, a detailed understanding of the anatomy, biomechanics, and morphological changes of the sternoclavicular joint during all stages of the osteoarthritic disease is essential for effective management to allow for maximum patient outcomes. This review explores the current literature on the anatomy of the sternoclavicular joint, starting with its structure and comparison to surrounding joints, biomechanics, and morphology, before considering the microanatomical changes that occur due to osteoarthritic degeneration. Early identification of osteoarthritic changes within this joint can enhance treatment and management outcomes before advancing joint degeneration, improving the quality of life for those affected.

Autoantibodies cause nociceptive sensitization in a mouse model of degenerative osteoarthritis

ABSTRACT

Previous preclinical and translational studies suggest that tissue trauma related to bony fracture and intervertebral disk disruption initiates the formation of pronociceptive antibodies that support chronic musculoskeletal pain conditions. This study tested this hypothesis in the monosodium iodoacetate (MIA) mouse model of osteoarthritis (OA) and extended the findings using OA patient samples. Monosodium iodoacetate was injected unilaterally into the knees of male and female wild-type (WT) and muMT mice (lacking B cells) to induce articular cartilage damage. Repeated nociceptive behavioral testing was performed, and serum was collected for antibody isolation and passive transfer experiments. Serum antibodies collected from patients with OA were tested in MIA-treated muMT mice. Biochemical analyses were performed on knee joint tissues. Monosodium iodoacetate-treated WT mice developed chronic ipsilateral hindlimb allodynia, hyperalgesia, and unweighting, but these pain behaviors were absent in MIA-treated muMT mice, indicating that cartilage injury-induced pain is B-cell dependent. IgM accumulation was observed in the knee tissues of MIA-treated mice, and intra-articular injection of IgM from MIA-treated mice into MIA-treated muMT mice caused nociceptive sensitization. Similarly, intra-articular injection of IgM from patients with OA was pronociceptive in muMT MIA mice and control subject IgM had no effect. Monosodium iodoacetate-injected joints demonstrate elevated levels of complement component 5a (C5a) and C5a receptor blockade using intra-articular PMX-53-reduced sensitization. These data suggest that MIA-treated mice and patients with OA generate pronociceptive antibodies, and further support the pronociceptive autoimmunity hypothesis for the transition from tissue injury to chronic musculoskeletal pain.

Genicular Artery embolisation in Patients with Osteoarthritis of the Knee (GENESIS) Using Permanent Microspheres: Long-Term Results

PURPOSE

To report the 2-year follow-up of patients with mild-to-moderate knee osteoarthritis (OA) treated with genicular artery embolisation (GAE) as part of the GENESIS study.

MATERIALS AND METHODS

Forty-six patients, median age = 60 (45-83) underwent GAE using permanent microspheres (100-300 μm). Technical success was defined as embolisation of the targeted genicular arteries. Knee Injury and Osteoarthritis Outcome Score (KOOS) and Visual Analogue Scale (VAS) (0-100 mm) were recorded at baseline, 6 weeks, 3 months, 1, 2 years. Contrast-enhanced MRI knee scans were acquired at baseline and 1 year, and evaluated with the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Functional MRI brain imaging and psychometric assessments were undertaken to investigate correlation between neuropsychological phenotypes and clinical outcome. Adverse events were recorded prospectively.

RESULTS

Technical success was achieved in forty patients (87%). Mean VAS improved from 58.63 (SD = 20.57, 95% CI 52.7-65.5) at baselines to 37.7 at 2-years (SD = 26.3, 95% CI 27.0-47.5). Whole and subgroup KOOS were significantly improved at each timepoint with associated reductions in analgesia usage. WORMS analysis demonstrated significant reduction in synovitis (p < 0.05) with no cases of osteonecrosis. Self-limiting skin discolouration occurred in four patients. A self-limiting groin haematoma and single case of deep-vein thrombosis due to immobilisation were also recorded. Nine patients subsequently underwent knee arthroplasty with no additional operational complexities identified. Neuropsychometric assessment elucidated a correlation between baseline catastrophising and greater reduction in pain post GAE.

CONCLUSION

GAE is a safe intervention for mild-moderate knee osteoarthritis, with sustained efficacy at 2 years. These results are promising and justify ongoing controlled trials.

TIPE2 gene transfer ameliorates aging-associated osteoarthritis in a progeria mouse model by reducing inflammation and cellular senescence

Osteoarthritis (OA) pain is often associated with the expression of tumor necrosis factor alpha (TNF-α), suggesting that TNF-α is one of the main contributing factors that cause inflammation, pain, and OA pathology. Thus, inhibition of TNF-α could potentially improve OA symptoms and slow disease progression. Anti-TNF-α treatments with antibodies, however, require multiple treatments and cannot entirely block TNF-α. TNF-α-induced protein 8-like 2 (TIPE2) was found to regulate the immune system's homeostasis and inflammation through different mechanisms from anti-TNF-α therapies. With a single treatment of adeno-associated virus (AAV)-TIPE2 gene delivery in the accelerated aging Zmpste24-/- (Z24-/-) mouse model, we found differences in Safranin O staining intensity within the articular cartilage (AC) region of the knee between TIPE2-treated mice and control mice. The glycosaminoglycan content (orange-red) was degraded in the Z24-/- cartilage while shown to be restored in the TIPE2-treated Z24-/- cartilage. We also observed that chondrocytes in Z24-/- mice exhibited a variety of senescent-associated phenotypes. Treatment with TIPE2 decreased TNF-α-positive cells, β-galactosidase (β-gal) activity, and p16 expression seen in Z24-/- mice. Our study demonstrated that AAV-TIPE2 gene delivery effectively blocked TNF-α-induced inflammation and senescence, resulting in the prevention or delay of knee OA in our accelerated aging Z24-/- mouse model.

Systematic review and network meta-analysis on the efficacy and safety of parmacotherapy for hand osteoarthritis

OBJECTIVE

Hand osteoarthritis poses a significant health challenge globally due to its increasing prevalence and the substantial burden on individuals and the society. In current clinical practice, treatment options for hand osteoarthritis encompass a range of approaches, including biological agents, antimetabolic drugs, neuromuscular blockers, anti-inflammatory drugs, hormone medications, pain relievers, new synergistic drugs, and other medications. Despite the diverse array of treatments, determining the optimal regimen remains elusive. This study seeks to conduct a network meta-analysis to assess the effectiveness and safety of various drug intervention measures in the treatment of hand osteoarthritis. The findings aim to provide evidence-based support for the clinical management of hand osteoarthritis.

METHODS

We performed a comprehensive search across PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials was conducted until September 15th, 2022, to identify relevant randomized controlled trials. After meticulous screening and data extraction, the Cochrane Handbook's risk of bias assessment tool was applied to evaluate study quality. Data synthesis was carried out using Stata 15.1 software.

RESULTS

21 studies with data for 3965 patients were meta-analyzed, involving 20 distinct Western medicine agents. GCSB-5, a specific herbal complex that mainly regulate pain in hand osteoarthritis, showed the greatest reduction in pain [WMD = -13.00, 95% CI (-26.69, 0.69)]. CRx-102, s specific medication characterized by its significant effect for relieving joint stiffness symptoms, remarkably mitigated stiffness [WMD = -7.50, 95% CI (-8.90, -6.10)]. Chondroitin sulfate displayed the highest incidence of adverse events [RR = 0.26, 95% CI (0.06, 1.22)]. No substantial variation in functional index for hand osteoarthritis score improvement was identified between distinct agents and placebo.

CONCLUSIONS

In summary, GCSB-5 and CRx-102 exhibit efficacy in alleviating pain and stiffness in HOA, respectively. However, cautious interpretation of the results is advised. Tailored treatment decisions based on individual contexts are imperative.

EEG-Based Cortical Alterations in Individuals With Chronic Knee Pain Secondary to Osteoarthritis: A Cross-sectional Investigation

Chronic painful knee osteoarthritis (OA) is a disabling physical health condition. Alterations in brain responses to arthritic changes in the knee may explain persistent pain. This study investigated source localized, resting-state electroencephalography activity and functional connectivity in people with knee OA, compared to healthy controls. Adults aged 44 to 85 years with knee OA (n = 37) and healthy control (n = 39) were recruited. Resting-state electroencephalography was collected for 10 minutes and decomposed into infraslow frequency (ISF) to gamma frequency bands. Standard low-resolution electromagnetic brain tomography statistical nonparametric maps were conducted, current densities of regions of interest were compared between groups and correlation analyses were performed between electroencephalography (EEG) measures and clinical pain and functional outcomes in the knee OA group. Standard low-resolution electromagnetic brain tomography nonparametric maps revealed higher (P = .006) gamma band activity over the right insula (RIns) in the knee OA group. A significant (P < .0001) reduction in ISF band activity at the pregenual anterior cingulate cortex, whereas higher theta, alpha, beta, and gamma band activity at the dorsal anterior cingulate cortex, pregenual anterior cingulate cortex, the somatosensory cortex, and RIns in the knee OA group were identified. ISF activity of the dorsal anterior cingulate cortex was positively correlated with pain measures and psychological distress scores. Theta and alpha activity of RIns were negatively correlated with pain interference. In conclusion, aberrations in infraslow and faster frequency EEG oscillations at sensory discriminative, motivational-affective, and descending inhibitory cortical regions were demonstrated in people with chronic painful knee OA. Moreover, EEG oscillations were correlated with pain and functional outcome measures. PERSPECTIVE: This study confirms alterations in the rsEEG oscillations and its relationship with pain experience in people with knee OA. The study provides potential cortical targets and the EEG frequency bands for neuromodulatory interventions for managing chronic pain experience in knee OA.

Inflammation in osteoarthritis: Our view on its presence and involvement in disease development over the years

Inflammation, both locally in the joint and systemic, is nowadays considered among the mechanisms involved in osteoarthritis (OA). However, this concept has not always been generally accepted. In fact, for long OA has been described as a relatively simple degeneration of articular cartilage as the result of wear and tear only. In this narrative review, we present what our understanding of OA was at the time of the inaugural release of Osteoarthritis and Cartilage about 30 years ago and discuss a set of pivotal papers that changed our view on the role of inflammation in OA development. Furthermore, we briefly discuss the current view on the involvement of inflammation in OA. Next, we use the example of transforming growth factor-β signaling to show how inflammation might influence processes in the joint in a manner that is beyond the simple interaction of ligand and receptor leading to the release of inflammatory and catabolic mediators. Finally, we discuss our view on what should be done in the future to bring the field forward.

Low-Level Laser Therapy for Thumb Carpometacarpal Joint Osteoarthritis: A Randomized Controlled Trial

Background and aim Low-level laser therapy (LLLT) is considered a promising non-invasive treatment option for osteoarthritis (OA). The current study aimed to evaluate the effectiveness of LLLT on patients with OA of the first carpometacarpal joint (CMC1) of the thumb. Methods An open-level, prospective, randomized controlled trial was conducted in the Department of Physical Medicine and Rehabilitation, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, for one year. Initially, 120 patients were approached for the study. Among them, 112 eligible patients were randomly divided into two groups: the intervention group received LLLT in addition to conservative treatment, while the control group received conservative treatment alone for four weeks. Pain and functional capability (motor) improvement were assessed on a weekly follow-up basis by using various parameters such as the visual analogue scale (VAS), Ritchie articular index (tenderness scale), grip strength, key pinch strength, Dreiser functional index, and CMC1 palmer abduction. Eventually, 90 patients completed the follow-ups and were included in the analysis. Results The majority of patients diagnosed with CMC1 joint OA were in their fifties. At baseline, patients of both intervention and control groups were indifferent in terms of demography, pain intensity, motor responses, and duration of suffering. After four weeks of treatment, results indicated an overall improvement in both groups. However, the reduction of pain and increase in functional capability were not found statistically significant (p-value: ≥0.5). Conclusion LLLT with conventional treatment was not found significantly more effective enough than conventional treatment alone, but more well-designed clinical trials with larger sample sizes are needed to reach a definitive conclusion.

Intra-articular injection of gold micro-particles with hyaluronic acid for painful knee osteoarthritis

BACKGROUND

Recently, in an open pilot study, we found up to two years, a potential pain-relieving effect of intra-articular gold micro-particles using the patient's synovial fluid for patients with knee osteoarthritis (KOA). During the study the excluded group of patients, due to multisite pain, co-morbidities, and other exclusion criteria., received intra-articular gold micro-particles using hyaluronic acid,. We aimed to identify if pre-treatment characteristics influence the global outcome two years after intra-articular treatment for painful KOA with gold microparticles using hyaluronic acid.

METHODS

Using hyaluronic acid as the carrier, 136 patients with KOA received intraarticular injections with 20 mg gold microparticles (72.000 particles, 20-40 μm in diameter). In the analysis, we included the Global Rating of Change Scale, Pain Detect Questionnaire (PDQ), Body Mass Index (BMI), and Kellgren & Lawrence score at the inclusion, Western Ontario, and McMaster Universities Osteoarthritis Index (WOMAC) sub-scores for pain, stiffness, and function at inclusion and two years.

RESULTS

On the Global Rating Change Scale, 69.1% of patients reported a positive effect, 28.7% no effect, and 2.2% worse. PDQ and the three WOMAC subscores all improved at two years of follow-up. PDQ ≥ 13 (P = 0.028), BMI (P = 0.022) and Kellgren & Lawrence grade 4 (P = 0.028) at inclusion reduced the effect with a minor odds ratio compared to the baseline effect of treatment (P = 0.025). WOMAC subscores at inclusion did not influence the outcome (P > 0.5).

CONCLUSIONS

Severe osteoarthritis, obesity, and neuropathic pain, reduced the effect of intra-articular gold microparticles for knee OA.

TRIAL REGISTRATION

The study followed the principles of the Declaration of Helsinki and was approved by the local ethics committee of the North Denmark Region by 27/07/2016 (N-20,160,045). The regional data protection agency approved the project by 06/07/2016 (2008-58-0028, ID 2016 - 116) and registered in ClinicalTrial.Gov by 04/01/2018 (NCT03389906).

Adhesive polydopamine-based photothermal hybrid hydrogel for on-demand lidocaine delivery, effective anti-bacteria, and prolonged local long-lasting analgesia

Considering the astonishing prevalence of localized pain affecting billions of patients worldwide, the development of advanced analgesic formulations or delivery systems to achieve clinical applicability is of great significance. In this study, an integrated PDA-based LiH@PDA@Ag@PAA@Gelatin system was designed for sustained delivery of lidocaine hydrochloride (LiH). By optimizing the preparation process and formulation of the hydrogel, the hydrogel exhibited superior mechanical properties, reversibility, adhesion strength, and self-healing attributes. Moreover, PDA@Ag nanoparticles were evenly dispersed within the hydrogel, and the optimized PDA@Ag@PAA@Gelatin showed a higher photothermal conversion efficiency than that of pure PDA. Importantly, LiH@PDA@Ag@PAA@Gelatin could effectively capture and eradicate bacteria through the synergistic interaction between near-infrared (NIR), PDA, Ag and LiH. In vitro and in vivo tests demonstrated that LiH@PDA@Ag@PAA@Gelatin exhibited higher drug delivery efficiency compared to commercial lidocaine patches. By evaluating the mechanical pain withdrawal threshold of the spared nerve injury (SNI) model in rats, it was proven that LiH@PDA@Ag@PAA@Gelatin enhanced and prolonged the analgesic effect of LiH. Furthermore, LiH@PDA@Ag@PAA@Gelatin induced by NIR possessed excellent on-demand photothermal analgesic ability. Therefore, this study develops a convenient method for preparing localized analgesic hydrogel patches, providing an important step towards advancing PDA-based on-demand pain relief applications.

Relationship between Nontraumatic Shoulder Disorders and Neuropathic Pain: Retrospective Observational Analyses of Clinical Features and Background Factors

Background

Accurate identification of neuropathic pain is necessary for appropriate treatment; however, the relationship between nontraumatic shoulder disorders and neuropathic pain remains unknown. Therefore, this retrospective observational study aimed to investigate the relationship, features, background factors, and prevalence of neuropathic pain among patients with nontraumatic shoulder disorders.

Methods

We evaluated 198 patients who visited our outpatient clinic, which specializes in shoulder disorders, from April 2015 to March 2016. The patients' age, sex, affected side, diagnosis, and pain duration were recorded, and the results of physical examination, including passive range of motion, impingement sign, and muscular strength assessments, were analyzed. The presence of neuropathic pain was assessed using the painDETECT questionnaire. Participants were divided into two groups according to the presence of neuropathic pain. Pain intensity was assessed using a visual analog scale, and the patient's mental status was assessed using the short-form McGill Pain Questionnaire and Hospital Anxiety and Depression Scale. The scores were compared between the groups.

Results

Neuropathic pain was observed in 7.6% of patients. The visual analog scale score for pain, short-form McGill Pain Questionnaire score, and Hospital Anxiety and Depression Scale score were significantly associated with the presence of neuropathic pain in the univariate analysis. Patient background factors and physical function were not associated with the presence of neuropathic pain. The prevalence of neuropathic pain in patients with frozen shoulder was 33.3%, which was significantly higher than that in patients with other shoulder disorders.

Conclusion

The occurrence of neuropathic pain may aggravate pain in patients with nontraumatic shoulder disorders. Neuropathic pain was not a rare condition in patients with nontraumatic shoulder disorders, particularly in those with frozen shoulder. The coexistence of neuropathic pain cannot be determined from background factors or physical function. Accurate diagnosis of neuropathic pain is essential in patients with nontraumatic shoulder disorders.

Heterogeneous Characteristics of the CD90+ Progenitors in the Fibrocartilage of Different Joints

OBJECTIVE

This study aimed to isolate and compare the mesenchymal stem cell characteristics of CD90+ cells from different fibrocartilage tissues in the temporomandibular joint (TMJ), the knee joint, and the intervertebral joint to further understand the similarities and differences of these 4 fibrocartilage tissues.

METHODS

CD90+ cells were isolated from TMJ disc, condylar cartilage, meniscus, and intervertebral disc by using magnetic-activated cell sorting. Cellular assays including 4.5-ethynyl-2'-deoxyuridine labeling, multilineage differentiation, colony formation, and cell migration were conducted to compare their mesenchymal stem cell characteristics. Immunofluorescent staining was performed for observing the expression of actively proliferating CD90+ cells within the tissues. H&E staining and Safranine O staining were used to compare the histological features.

RESULTS

The CD90+ cells derived from these 4 fibrocartilage tissues exhibited comparable cell proliferation abilities. However, the cells from the TMJ disc displayed limited multilineage differentiation potential, colony formation, and cell migration abilities in comparison with the cells from the other fibrocartilage tissues. In vivo, there was relatively more abundant expression of CD90+ cells in the TMJ disc during the early postnatal stage. The limited EDU+ cell numbers signified a low proliferation capacity of CD90+ cells in the TMJ disc. In addition, we observed a significant decrease in cell density and a restriction in the synthesis of extracellular proteoglycans in the TMJ disc.

CONCLUSION

Our study highlights the spatial heterogeneity of CD90+ cells in the fibrocartilages of different joint tissues, which may contribute to the limited cartilage repair capacity in the TMJ disc.

Detection of brain regions responsible for chronic pain in osteoarthritis: an fMRI-based neuroimaging study using deep learning

Introduction

Chronic pain is a multifaceted condition that has yet to be fully comprehended. It is frequently linked with a range of disorders, particularly osteoarthritis (OA), which arises from the progressive deterioration of the protective cartilage that cushions the bone endings over time.

Methods

In this paper, we examine the impact of chronic pain on the brain using advanced deep learning (DL) algorithms that leverage resting-state functional magnetic resonance imaging (fMRI) data from both OA pain patients and healthy controls. Our study encompasses fMRI data from 51 pain patients and 20 healthy subjects. To differentiate chronic pain-affected OA patients from healthy controls, we introduce a DL-based computer-aided diagnosis framework that incorporates Multi-Layer Perceptron and Convolutional Neural Networks (CNN), separately.

Results

Among the examined algorithms, we discovered that CNN outperformed the others and achieved a notable accuracy rate of nearly 85%. In addition, our investigation scrutinized the brain regions affected by chronic pain and successfully identified several regions that have not been mentioned in previous literature, including the occipital lobe, the superior frontal gyrus, the cuneus, the middle occipital gyrus, and the culmen.

Discussion

This pioneering study explores the applicability of DL algorithms in pinpointing the differentiating brain regions in OA patients who experience chronic pain. The outcomes of our research could make a significant contribution to medical research on OA pain patients and facilitate fMRI-based pain recognition, ultimately leading to enhanced clinical intervention for chronic pain patients.

Global trends in research on extracorporeal shock wave therapy (ESWT) from 2000 to 2021

BACKGROUND

This study intended to analyze the application of extracorporeal shock wave therapy in medicine and to evaluate the quality of related literature.

METHODS

All publications were extracted from 2000 to 2021 from the Web of Science Core Collection (WoSCC). The literature characteristics were depicted by VOSviewer (version 1.6.15) and the online bibliometric website ( http://bibliometric.com/ ). The future trends and hotspots were conducted by Bibliographic Item Co-occurrence Matrix Builder (version 2.0) and gCLUTO software.

RESULTS

We analyzed 1774 articles corresponding to the criteria for ESWT publications from 2000 to 2021. Most studies were conducted within the United States and China which besides have the most cooperation. The most published research institutions are Chang Gung University, Kaohsiung Chang Gung Memorial Hospital, and Kaohsiung Medical University. Six research hotspots were identified by keyword clustering analysis: Cluster0: The effects of ESWT on muscle spasticity; Cluster1: The application of ESWT in osteoarthritis (OA); Cluster2: Therapeutic effect of ESWT on tendon diseases; Cluster3: Early application of ESWT/ESWL in urolithiasis; Cluster4: The Role of angiogenesis in ESWT and the efficiency of ESWT for penile disease; Cluster5: The Special value of radial extracorporeal shock wave therapy (rESWT).

CONCLUSIONS

A comprehensive and systematic bibliometric analysis of ESWT was conducted in our study. We identified six ESWT-related research hotspots and predicted future research trends. With the gradual increase of research on ESWT, we find that ESWT is used more and more extensively, such in musculoskeletal disease, bone delay union, neurological injury, andrology disorders, lymphedema, and so on. In addition, the mechanism is not destructive damage, as initially thought, but a restorative treatment. Furthermore, delayed union, cellulite, burn, and diabetic foot ulcers may be the future direction of scientific study.

Evaluation of the effect of physical therapy on pain and dysfunction of knee osteoarthritis based on fNIRS: a randomized controlled trial protocol

BACKGROUND

Knee osteoarthritis (KOA) is a chronic musculoskeletal disease that can cause joint pain and dysfunction, affecting the quality of life of patients. Nonsurgical treatment is the conventional treatment of KOA, among which physical therapy is widely used because of its simplicity, convenience and effectiveness. The functional biomarker will add to the clinical fidelity and diagnostic accuracy. Therefore, our study chose a more objective evaluation indicator, functional near-infrared spectroscopy (fNIRS), to identify between healthy people and KOA patients, and to detect the pain change before and after treatment of KOA patients.

METHODS

The study will be conducted in the Rehabilitation Medical Center of West China Hospital of Sichuan University and divided into 2 stages. In the first stage, we will compare and determine the differences in baseline data between healthy volunteers and KOA patients. In the second stage, 72 KOA patients will be randomly divided into two groups: the drug therapy group (DT) and the combination therapy group (CT) for 10 treatments. Outcome measures will be measured at baseline and on the 5th and 10th days after the intervention, including the numerical rating scale (NRS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), pain catastrophizing scale (PCS), the association of pain severity with task-state functional connectivity fNIRS and association of pain severity with task-activated fNIRS.

DISCUSSION

By analyzing the fNIRS data of healthy volunteers and KOA patients, our study will be determined whether fNIRS can be used as a new indicator to reflect the severity of pain in KOA patients. Subsequently, the same fNIRS data for KOA patients before and after the intervention will be collected to provide an accurate evaluation criterion for the effect of physical therapy on KOA.

TRIAL REGISTRATION

The study was registered on the Chinese Registry website (registered in ChiCTR.org with the identifiers ChiCTR2200064175 and 29/09/2022).

Human synovial fluid interleukin-6, but not type II collagen breakdown, positively correlated with pain after anterior cruciate ligament injury and reconstruction

Anterior cruciate ligament (ACL) injury initiates a biochemical cascade thought to contribute to the onset and progression of posttraumatic osteoarthritis (PTOA). Interleukin-1ß (IL-1ß), IL-6, and C-telopeptide fragments of type II collagen (CTX-II) are implicated in joint inflammation and cartilage degradation following ACL injury; however, their association with pain is still being explored. The purpose of this study was to evaluate the associations between synovial fluid concentrations of IL-1ß, IL-6, and CTX-II with pain following ACL injury and reconstruction. We hypothesized that greater IL-1ß, IL-6, and CTX-II would correlate with greater Pain Visual Analogue Scale (VAS) scores. This was a secondary analysis of 23 patients (mean age = 18.4 years, BMI = 27.4, 13 females/10 males) with acute ACL tears who participated in a pilot randomized trial. Synovial fluid and VAS scores were collected on the day of initial presentation, at ACL reconstruction, and 1 and 4 weeks after surgery. Synovial fluid concentrations of IL-1ß, IL-6, and CTX-II were assessed using enzyme-linked immunoabsorbent assays, and repeated measures correlations were used to assess the relationships between pain and synovial IL-1ß, IL-6, or CTX-II after ACL injury and reconstruction. Pain was positively correlated with synovial fluid IL-6 concentrations (r = 0.52, p < 0.001); however, pain was inversely correlated with CTX-II (r = -0.39, p = 0.002). IL-1ß had no significant correlation with pain. Statement of clinical relevance: PTOA has been described as a "silent killer" and these results suggest that early PTOA may have pro-inflammatory pathways that are not primarily associated with pain but still lead to progressive cartilage loss.

The Short-Term Efficacy of Large-Focused and Controlled-Unfocused (Radial) Extracorporeal Shock Wave Therapies in the Treatment of Hip Osteoarthritis

Although the classical treatments listed in the guidelines for osteoarthritis are widely used, the majority of patients do not fully recover from their pain. It is a fact that new treatment methods are needed both to relieve pain and restore deteriorated joint function. No study has been found to date that evaluated the efficacy of ESWT in hip OA. This pilot trial is the first in the literature to investigate the comparative effects of the two ESWT types (f-ESWT and r-ESWT) in the treatment of hip OA. Briefly, 148 patients were randomly distributed into the three ESWT groups: focused (f-ESWT), radial (r-ESWT), and sham (s-ESWT). Patients were assessed with the Visual Analog Scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores just before the treatment (0 week), just after the treatment (4th week), and 1 month after completion of the treatment (8th week). VAS and all WOMAC scores were significantly reduced at follow-up points (4th and 8th weeks) in both the f-ESWT and r-ESWT groups compared with baseline (0 week) (for all, p < 0.001). Statistical comparisons between the f-ESWT and r-ESWT groups showed that f-ESWT was superior to r-ESWT for the decrease in VAS and WOMAC scores from baseline to the 4th and 8th weeks (p < 0.001 or p < 0.002). Both r-ESWT and f-ESWT were found to have significant treatment efficacy compared with s-ESWT. However, f-ESWT produced a superior improvement in follow-up parameters compared to r-ESWT.

Functional outcomes in patient specific instrumentation vs. conventional instrumentation for total knee arthroplasty; a systematic review and meta-analysis of prospective studies

Background

Total Knee Arthroplasty (TKA) is an established surgical option for knee osteoarthritis (OA). There are varying perceptions of the most suitable surgical technique for making bone cuts in TKA. Conventional Instrumentation (CI) uses generic cutting guides (extra- and intra-medullary) for TKA; however, patient specific instrumentation (PSI) has become a popular alternative amongst surgeons.

Methods

A literature search of electronic databases Embase, Medline and registry platform portals was conducted on the 16^th May 2021. The search was performed using a predesigned search strategy. Eligible studies were critically appraised for methodological quality. The primary outcome measure was Knee Society Function Score. Functional scores were also collected for the secondary outcome measures: Oxford Knee Score (OKS), Western Ontario and McMaster Universities Arthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Visual Analog Scale (VAS) for pain. Review Manager 5.3 was used for all data synthesis and analysis.

Results

There is no conclusive evidence in the literature to suggest that PSI or CI instrumentation is better for functional outcomes. 23 studies were identified for inclusion in this study. Twenty-two studies (18 randomised controlled trials and 4 prospective studies) were included in the meta analysis, with a total of 2277 total knee arthroplasties. There were 1154 PSI TKA and 1123 CI TKA. The majority of outcomes at 3-months, 6-months and 12 show no statistical difference. There was statistical significance at 24 months in favour of PSI group for KSS function (mean difference 4.36, 95% confidence interval 1.83–6.89). The mean difference did not exceed the MCID of 6.4. KSS knee scores demonstrated statistical significance at 24 months (mean difference 2.37, 95% confidence interval (CI) 0.42—4.31), with a MCID of 5.9. WOMAC scores were found to be statistically significant favouring PSI group at 12 months (mean difference -3.47, 95% confidence interval (CI) -6.57- -0.36) and 24 months (mean difference -0.65, 95% confidence interval (CI) -1.28—-0.03), with high level of bias noted in the studies and a MCID of 10.

Conclusions

This meta-analysis of level 1 and level 2 evidence shows there is no clinical difference when comparing PSI and CI KSS function scores for TKA at definitive post operative time points (3 months, 6 months, 12 months and 24 months). Within the secondary outcomes for this study, there was no clinical difference between PSI and CI for TKA. Although there was no clinical difference between PSI and CI for TKA, there was statistical significance noted at 24 months in favour of PSI compared to CI for TKA when considering KSS function, KSS knee scores and WOMAC scores. Studies included in this meta-analysis were of limited cohort size and prospective studies were prone to methodological bias. The current literature is limited and insufficiently robust to make explicit conclusions and therefore further high-powered robust RCTs are required at specific time points.

Associations between biomarkers of matrix metabolism and inflammation with pain and fatigue in participants suspected of early hip and or knee osteoarthritis: data from the CHECK study

OBJECTIVES

To assess the associations of biomarkers in serum [highsensitivity C-reactive protein (hs-CRP), serum cartilage oligomeric protein (sCOMP), serum propeptide of type I procollagen (sPINP) and serum osteocalcin (sOC)] and urine [urinary type II collagen telopeptide (uCTX-2)] with the extent and progression of nocturnal pain, pain while walking, and fatigue in participants with hip and/or knee pain suspected to be early stage osteoarthritis (OA).

METHODS

hs-CRP, uCTX-2, sCOMP, sPINP and sOC were measured at baseline in 1,002 participants of the Cohort Hip and Cohort Knee (CHECK). Nocturnal pain, pain while walking and fatigue were assessed by self-reported questionnaires at baseline and 2-year follow-up. Associations between these biomarkers and symptoms were examined using logistic and linear regression analyses.

RESULTS

hs-CRP was significantly associated with mild nocturnal pain (OR 1.18 95% CI 1.01-1.37), with mild and moderate pain while walking (OR 1.17 95% CI 1.01-1.35 and OR 1.56 95% CI 1.29-1.90, respectively) and with progression of nocturnal pain (OR 1.25 95% CI 1.07-1.46). uCTX-2 was associated with mild nocturnal pain (OR 1.40 95% CI 1.05-1.85) and with mild and severe-extreme pain while walking (OR 1.35 95% CI 1.04-1.75 and OR 2.55 95% CI 1.03-6.34, respectively). sPINP was associated with severe-extreme nocturnal pain (OR 0.45 95% CI 0.25-0.82). No significant associations were found for sCOMP and sOC, nor for any of the biomarkers and fatigue.

CONCLUSION

This study of biomarkers in a large cohort of participants with hip and/or knee pain suspected to reflect early stage hip and/or knee OA suggests that inflammation and cartilage matrix degeneration play a role in pain, but not in fatigue.

Morphological and Mechanical Characterization of Extracellular Vesicles and Parent Human Synoviocytes under Physiological and Inflammatory Conditions

The morphology of fibroblast-like synoviocytes (FLS) issued from the synovial fluid (SF) of patients suffering from osteoarthritis (OA), rheumatoid arthritis (RA), or from healthy subjects (H), as well as the ultrastructure and mechanical properties of the FLS-secreted extracellular vesicles (EV), were analyzed by confocal microscopy, transmission electron microscopy, atomic force microscopy, and tribological tests. EV released under healthy conditions were constituted of several lipid bilayers surrounding a viscous inner core. This "gel-in" vesicular structure ensured high mechanical resistance of single vesicles and good tribological properties of the lubricant. RA, and to a lesser extent OA, synovial vesicles had altered morphology, corresponding to a "gel-out" situation with vesicles surrounded by a viscous gel, poor mechanical resistance, and poor lubricating qualities. When subjected to inflammatory conditions, healthy cells developed phenotypes similar to that of RA samples, which reinforces the importance of inflammatory processes in the loss of lubricating properties of SF.

Association of Biomarkers with Individual and Multiple Body Sites of Pain: The Johnston County Osteoarthritis Project

Introduction

Biochemical biomarkers may provide insight into musculoskeletal pain reported at individual or multiple body sites. The purpose of this study was to determine if biomarkers or pressure-pain threshold (PPT) were associated with individual or multiple sites of pain.

Methods

This cross-sectional analysis included 689 community-based participants. Self-reported symptoms (ie, pain, aching, or stiffness) were ascertained about the neck, upper back/thoracic, low back, shoulders, elbows, wrist, hands, hips, knees, ankles, and feet. Measured analytes included CXCL-6, RANTES, HA, IL-6, BDNF, OPG and NPY. A standard dolorimeter measured PPT. Logistic regression was used determine the association between biomarkers and PPT with individual and summed sites of pain.

Results

Increased IL-6 and HA were associated with knee pain (OR=1.30, 95% CI 1.03, 1.64) and (OR=1.32, 95% CI 1.01, 1.73) respectively; HA was also associated with elbow/wrist/hand pain (OR=1.60, 95% CI 1.22, 2.09). Those with increased NPY levels were less likely to have shoulder pain (OR=0.56, 95% CI 0.33, 0.93). Biomarkers HA (OR=1.50, 95% CI 1.07, 2.10), OPG (OR=1.74, 95% CI 1.00, 3.03), CXCL-6 (OR=1.75, 95% CI 1.02, 3.01) and decreased PPT (OR=3.97, 95% CI 2.22, 7.12) were associated with multiple compared to no sites of pain. Biomarker HA (OR=1.57, 95% CI 1.06, 2.32) and decreased PPT (OR=3.53, 95% CI 1.81, 6.88) were associated with multiple compared to a single site of pain.

Conclusion

Biomarkers of inflammation (HA, OPG, IL-6 and CXCL-6), pain (NPY) and PPT may help to understand the etiology of single and multiple pain sites.

Source localized infraslow neurofeedback training in people with chronic painful knee osteoarthritis: A randomized, double-blind, sham-controlled feasibility clinical trial

Persistent pain is a key symptom in people living with knee osteoarthritis (KOA). Infra-slow Neurofeedback (ISF-NF) training is a recent development focusing on modulating cortical slow-wave activity to improve pain outcomes. A parallel, two-armed double-blinded, randomized sham-controlled, feasibility clinical trial aimed to determine the feasibility and safety of a novel electroencephalography-based infraslow fluctuation neurofeedback (EEG ISF-NF) training in people with KOA and determine the variability of clinical outcomes and EEG changes following NF training. Eligible participants attended nine 30-min ISF-NF training sessions involving three cortical regions linked to pain. Feasibility measures were monitored during the trial period. Pain and functional outcomes were measured at baseline, post-intervention, and follow-up after 2 weeks. Resting-state EEG was recorded at baseline and immediate post-intervention. Participants were middle-aged (61.7 ± 7.6 years), New Zealand European (90.5%), and mostly females (62%) with an average knee pain duration of 4 ± 3.4 years. The study achieved a retention rate of 91%, with 20/22 participants completing all the sessions. Participants rated high levels of acceptance and “moderate to high levels of perceived effectiveness of the training.” No serious adverse events were reported during the trial. Mean difference (95% CI) for clinical pain and function measures are as follows for pain severity [active: 0.89 ± 1.7 (−0.27 to 2.0); sham: 0.98 ± 1.1 (0.22–1.7)], pain interference [active: 0.75 ± 2.3 (−0.82 to 2.3); Sham: 0.89 ± 2.1 (−0.60 to 2.4)], pain unpleasantness [active: 2.6 ± 3.7 (0.17–5.1); sham: 2.8 ± 3 (0.62–5.0)] and physical function [active: 6.2 ± 13 (−2.6 to 15); sham: 1.6 ± 12 (−6.8 to 10)]. EEG sources demonstrated frequency-specific neuronal activity, functional connectivity, and ISF ratio changes following NF training. The findings of the study indicated that the ISF-NF training is a feasible, safe, and acceptable intervention for pain management in people with KOA, with high levels of perceived effectiveness. The study also reports the variability in clinical, brain activity, and connectivity changes following training.

Characteristic Bone Morphology Change of the Subtalar Joint in Severe Varus Ankle Osteoarthritis

The subtalar joint has a possible compensatory mechanism for supramalleolar deformities; the failure of this mechanism causes the progression of ankle osteoarthritis. However, the reason for this failure has not been fully elucidated. This study aimed to evaluate the characteristics of the morphologic changes in the subtalar joint in varus ankle osteoarthritis using computed tomography. The study included 30 patients with severe osteoarthritis (modified Kellgren-Lawrence classification grade ≥ 3; mean age: 68.5 years) and 30 patients without- or with early osteoarthritis (grade 0-1; mean age: 43.0 years) as the control group. The location of cysts, osteophyte formation in the subtalar joint, and thickness of the subchondral bone plate were evaluated. In the osteoarthritis group, cyst formation was observed on the posterolateral side of the posterior facet of the calcaneus in 6 cases (20%) and of the talus in 7 cases (23.3%). Osteophyte formation was observed in the talus in 21 cases (70.0%) and in the calcaneus in 29 cases (96.6%). Osteophyte formation was observed on the posterior or lateral side of the posterior facet, and osteophyte contact between the talus and calcaneus was observed. The subchondral bone plate of the posterior medial side of the posterior facet of the talus was significantly thicker in the osteoarthritis group. The subtalar joint is less affected in severe varus ankle osteoarthritis containing a thickened subchondral bone plate in the posteromedial aspect of the posterior talar facet.

Impact of pain sensitisation on the quality of life of patients with knee osteoarthritis

Objectives

We aim to evaluate the effect on different ways of classifying pain sensitisation on impact and quality of life (QoL) in knee osteoarthritis (KOA).

Methods

We used baseline data from a cohort of consecutive patients with KOA listed for arthroplasty. We collected demographics and number of painful body sites. We measured pressure pain thresholds at the right forearm (PPT_arm). Pain sensitisation was classified using: (1) widespread pain, (2) lowest 10th percentile of PPT_arm and (3) PainDETECT questionnaire ≥13/38. Impact and QoL were assessed using Western Ontario and McMaster Universities Osteoarthritis Index and Short Form-36. Impact and QoL scores in patients with or without pain sensitisation were compared. We evaluated the association of pain sensitisation measures with QoL scores using multivariable regression.

Results

233 patients (80% female, mean age 66 years) included in the analysis; 7.3%, 11.6% and 4.7% were classified as having pain sensitisation by widespread pain, low PPT_arm and PainDETECT criteria, respectively. There was minimal overlap of patients as classified as pain sensitisation phenotype by different measures. Patients with pain sensitisation had poorer QoL compared with those without. Low PPT_arm identified patients with poorer general health, while widespread pain and PainDETECT identified poorer QoL in more psychological domains. There was weak correlation between number of painful body sites and PainDETECT (rho=0.23, p<0.01), but no significant correlation with PPT_arm.

Conclusion

Patients with KOA with pain sensitisation have poorer QoL compared with those without, regardless of classification method. Different criteria defined patients with different pattern of QoL impact.

Phytochemicals Mediate Autophagy Against Osteoarthritis by Maintaining Cartilage Homeostasis

Osteoarthritis (OA) is a common degenerative joint disease and is a leading cause of disability and reduced quality of life worldwide. There are currently no clinical treatments that can stop or slow down OA. Drugs have pain-relieving effects, but they do not slow down the course of OA and their long-term use can lead to serious side effects. Therefore, safe and clinically appropriate long-term treatments for OA are urgently needed. Autophagy is an intracellular protective mechanism, and targeting autophagy-related pathways has been found to prevent and treat various diseases. Attenuation of the autophagic pathway has now been found to disrupt cartilage homeostasis and plays an important role in the development of OA. Therefore, modulation of autophagic signaling pathways mediating cartilage homeostasis has been considered as a potential therapeutic option for OA. Phytochemicals are active ingredients from plants that have recently been found to reduce inflammatory factor levels in cartilage as well as attenuate chondrocyte apoptosis by modulating autophagy-related signaling pathways, which are not only widely available but also have the potential to alleviate the symptoms of OA. We reviewed preclinical studies and clinical studies of phytochemicals mediating autophagy to regulate cartilage homeostasis for the treatment of OA. The results suggest that phytochemicals derived from plant extracts can target relevant autophagic pathways as complementary and alternative agents for the treatment of OA if subjected to rigorous clinical trials and pharmacological tests.

Mechanism of Chronic Pain of Symptomatic Hip Osteoarthritis by Association of its Distribution, Nociceptive, Neuropathic, Nociplastic, or Mixed-pain Screening, and the Prevalence of Lumbar Spinal Stenosis: A Cross-sectional Study

OBJECTIVES

The pain of hip osteoarthritis (OA) is generally recognized as nociceptive in origin because of the local pathology. However, some patients with OA experience a neuropathic pain component as an essential part of some nociplastic pain subtype. Here, we sought to examine the mechanism of chronic pain of symptomatic hip OA by the association of its distribution, complex pain mechanism screening, and the prevalence of lumbar spinal stenosis.

MATERIALS AND METHODS

We conducted a prospective cross-sectional study of 100 hips in 100 patients with symptomatic hip OA in a chronic state. We examined all baseline clinical characteristics including clinical and functional score, location of pain and numbness, and pain score (PainDETECT questionnaire and the Leeds Assessment of Neuropathic Symptoms and Signs), and magnetic resonance imaging of the hip and lumbar spine.

RESULTS

The PainDETECT questionnaire and Leeds Assessment of Neuropathic Symptoms and Signs revealed that 23% of the patients had a neuropathic pain component. There were 24 variations of the pain pattern. By contrast, the pain localized around the hip joint was only 15%. Pain distal to the thigh and any numbness was significantly more frequent in the group with neuropathic pain (P<0.001). Lumbar spinal stenosis grade was not significantly different between patients with nociceptive pain and those with neuropathic pain. Pain score was significantly correlated with the pain in clinical and functional scores.

DISCUSSION

Among patients with symptomatic hip OA, the distribution of pain was various, and about 23% of patients had neuropathic, nociplastic, or mixed pain as a possibility for somatosensory system disturbances.

The Expressions of Dickkopf-Related Protein 1 and Frizzled-Related Protein Are Negatively Correlated to Local Inflammation and Osteoarthritis Severity

OBJECTIVE

To investigate the presence of WNT antagonists Dickkopf-related protein 1 (DKK1), Frizzled-related protein (FRZB) and BMP antagonist Gremlin 1 (GREM1) in synovial fluid (SF) and serum, respectively, from end-stage knee osteoarthritis (OA) patients, and correlate their expression with other markers of OA.

DESIGN

In a cross-sectional study, SF and serum were collected from OA patients (n = 132). The concentrations of DKK1, FRZB and GREM1 in SF and serum were determined using immunoassays. Correlation measurements were performed between groups and previously assessed disease markers, such as synovium nitric oxide (NO), inerleukin-1β (IL1β), tumor necrosis factor-α (TNFα), and prostaglandin E2 (PGE2).

RESULTS

The OA patients with the celecoxib treatment till surgery have higher median SF FRZB values compared with the control (no treatment); the celecoxib 3-days before surgery stopped treatment group has higher median serum FRZB values than the control and the naproxen treatment group. The combinational analysis of SF DKK1 and SF FRZB negatively correlated with macroscopic cartilage scores and histological synovium scores in OA patients. The expression of DKK1 and FRZB in SF showed the same expression trend as their expression in serum. Furthermore, the SF concentration of DKK1 was positively correlated with FRZB in both SF and serum. In contrast, it was negatively correlated with synovium NO and IL1β. SF FRZB was negatively correlated with synovium NO, IL1β, cartilage PGE2, and age.

CONCLUSIONS

Our findings suggest DKK1 and FRZB were negatively correlated with OA severity and multiple pro-inflammatory cytokines. Our data indicate that DKK1 and FRZB can be joint disease-specific biomarkers.

Phytochemical Analysis and Anti-Inflammatory and Anti-Osteoarthritic Bioactive Potential of Verbascum thapsus L. (Scrophulariaceae) Leaf Extract Evaluated in Two In Vitro Models of Inflammation and Osteoarthritis

Osteoarthritis (OA) is a complex disease, source of pain and disability that affects millions of people worldwide. OA etiology is complex, multifactorial and joint-specific, with genetic, biological and biomechanical components. Recently, several studies have suggested a potential adjuvant role for natural extracts on OA progression, in terms of moderating chondrocyte inflammation and following cartilage injury, thus resulting in an overall improvement of joint pain. In this study, we first analyzed the phenylethanoid glycosides profile and the total amount of polyphenols present in a leaf aqueous extract of Verbascum thapsus L. We then investigated the anti-inflammatory and anti-osteoarthritic bioactive potential of the extract in murine monocyte/macrophage-like cells (RAW 264.7) and in human chondrocyte cells (HC), by gene expression analysis of specifics inflammatory cytokines, pro-inflammatory enzymes and metalloproteases. Six phenylethanoid glycosides were identified and the total phenolic content was 124.0 ± 0.7 mg gallic acid equivalent (GAE)/g of extract. The biological investigation showed that the extract is able to significantly decrease most of the cellular inflammatory markers, compared to both control cells and cells treated with Harpagophytum procumbens (Burch.) DC. ex Meisn, used as a positive control. Verbascum thapsus leaf aqueous extract has the potential to moderate the inflammatory response, representing an innovative possible approach for the inflammatory joint disease treatment.

The Association of Osteoarthritis and Related Pain Burden to Incident Alzheimer's Disease and Related Dementias: A Retrospective Cohort Study of U.S. Medicare Beneficiaries

BACKGROUND

Emerging evidence suggests osteoarthritis (OA) and related symptom burden may increase risk for Alzheimer's disease and related dementias (ADRD). However, longitudinal studies are sparse, and none have examined the potential mediating effects of mood or sleep disorders.

OBJECTIVE

To determine the association of OA and related pain to incident ADRD in U.S. elders.

METHODS

In this retrospective cohort study, we used baseline and two-year follow-up data from linked Medicare claims and Medicare Current Beneficiary Survey files (11 pooled cohorts, 2001-2013). The study sample comprised 16,934 community-dwelling adults≥65 years, ADRD-free at baseline and enrolled in fee-for-service Medicare. Logistic regression was used to assess the association of OA and related pain (back, neck, joint, neuropathic) to incident ADRD, explore the mediating inlfuence of mood and insomnia-related sleep disorders, and (sensitivity analyses) account for potential survival bias.

RESULTS

Overall, 25.5% of beneficiaries had OA at baseline (21.0% with OA and pain); 1149 elders (5.7%) were subsequently diagnosed with ADRD. Compared to beneficiaries without OA, those with OA were significantly more likely to receive a diagnosis of incident ADRD after adjustment for sociodemographics, lifestyle characteristics, comorbidities, and medications (adjusted odds ratio (AOR) = 1.23 (95% confidence interval (CI) 1.06, 1.42). Elders with OA and pain at baseline were significantly more likely to be diagnosed with incident ADRD than were those without OA or pain (AOR = 1.31, CI 1.08, 1.58). Sensitivity analyses yielded similar findings. Inclusion of depression/anxiety, but not sleep disorders, substantially attenuated these associations.

CONCLUSION

Findings of this study suggest that: OA is associated with elevated ADRD risk, this association is particularly pronounced in those with OA and pain, and mood disorders may partially mediate this relationship.

Predictors of a placebo response in patients with hand osteoarthritis: post-hoc analysis of two randomized controlled trials

BACKGROUND

Placebo can have a significant therapeutic effect in patients with hand osteoarthritis (OA). This aim of the study is to identify factors associated with a clinically meaningful placebo response in patients with hand OA.

METHODS

This post-hoc analysis of two double-blind, placebo-controlled, randomized trials (RCTs) investigating the efficacy of GCSB-5 or diacerein as treatments for hand OA analyzed the efficacy of a placebo. Clinical and laboratory factors associated with a clinically meaningful response, defined as an improvement in the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) pain score > 10 at 4 weeks relative to baseline, were identified.

RESULTS

The mean improvement in the AUSCAN pain score was - 6.0 ± 20.3, with marked variation between 143 hand OA patients (range: - 76.4 to 33.2). A clinically meaningful improvement was observed in 54 (37.8%) patients. Placebo responders had worse AUSCAN pain scores (55.7 ± 19.7 vs. 43.6 ± 21.6, p = 0.001) and a worse AUSCAN stiffness (68.2 ± 20.5 vs. 57.5 ± 24.5, p = 0.008) at baseline than non-responders. Improvements in pain correlated with the baseline pain level (Pearson r = - 427, p < 0.001). Structural joint changes such as tender, swollen, enlarged, or deformed joint counts did not differ between placebo responders and non-responders. In a multivariable analysis, only baseline AUSCAN pain was associated with a clinically meaningful placebo response (OR: 1.054, 95% CI [1.019-1.089], p = 0.002).

CONCLUSIONS

High levels of pain at baseline are predictive of a clinically meaningful placebo response in patients with hand OA. Further studies are needed to optimize and utilize the benefit of placebo responses in patients with hand OA.

Neuronal interleukin-1 receptors mediate pain in chronic inflammatory diseases

Chronic pain is a major comorbidity of chronic inflammatory diseases. Here, we report that the cytokine IL-1β, which is abundantly produced during multiple sclerosis (MS), arthritis (RA), and osteoarthritis (OA) both in humans and in animal models, drives pain associated with these diseases. We found that the type 1 IL-1 receptor (IL-1R1) is highly expressed in the mouse and human by a subpopulation of TRPV1⁺ dorsal root ganglion neurons specialized in detecting painful stimuli, termed nociceptors. Strikingly, deletion of the Il1r1 gene specifically in TRPV1⁺ nociceptors prevented the development of mechanical allodynia without affecting clinical signs and disease progression in mice with experimental autoimmune encephalomyelitis and K/BxN serum transfer–induced RA. Conditional restoration of IL-1R1 expression in nociceptors of IL-1R1–knockout mice induced pain behavior but did not affect joint damage in monosodium iodoacetate–induced OA. Collectively, these data reveal that neuronal IL-1R1 signaling mediates pain, uncovering the potential benefit of anti–IL-1 therapies for pain management in patients with chronic inflammatory diseases.

The physiopathology of osteoarthritis: Paleopathological implications of non-articular lesions from a modern surgical sample

OBJECTIVES

This research focused on osteoarthritis (OA) lesions on modern patients to 1) identify consistently observed lesions not included within current paleopathological measures of OA, 2) assess the correspondence of bone and cartilage lesions with clinical OA diagnostic criteria, and 3) discuss the correspondence of bone lesions with sources of pain reported in clinical literature.

MATERIALS

Tibial plateaus from 62 patients undergoing total knee replacement surgery due to OA were examined.

METHODS

Plateaus were scored for several non-standard OA criteria, including non-articular and X-ray visible lesions and pre-maceration cartilage lesions, as well as articular surface criteria standard in paleopathology.

RESULTS

Proliferative bone in the intercondylar region was present in 95 % of specimens, while areas of dense trabecular bone and lytic defects, both on the inferior side of the plateaus, were present in 98 % and 83 %, respectively.

CONCLUSIONS

The inferior lytic defects may be physical evidence of bone marrow lesions (BML), a clinical OA indicator visible via MRI. Previous research has linked BML to pain, inflammation, and ligament pathology. The latter conditions have also been associated with intercondylar enthesophytes and third intercondylar tubercle of Parsons (TITP), both of which were observed in the intercondylar regions.

SIGNIFICANCE

Several non-articular lesions not currently included in paleopathological measures of OA were consistently observed.

SUGGESTIONS FOR FUTURE RESEARCH

A similar analysis of a control sample of non-OA tibial plateaus would better contextualize these results.

LIMITATIONS

The sample's high average age (65.8 years) and severe OA stage may hamper generalizability to archaeological collections.

Anti-osteoarthritis potential of peppermint and rosemary essential oils in a nanoemulsion form: behavioral, biochemical, and histopathological evidence

BACKGROUND

This study aimed to evaluate the effect of nanoemulsion containing peppermint and rosemary essential oils in rats with osteoarthritis (OA).

METHODS

In this experimental study, we prepared a nanoemulsion containing peppermint and rosemary essential oils by spontaneous emulsification and evaluated the nanoemulsion's dermal irritation and toxicity. Investigating the analgesic effect of the nanoemulsion, we randomly assigned 36 male rats to 6 groups: Control (saline injection into the knee), osteoarthritis (intra-articular injection of 2 mg monosodium iodoacetate), and four groups of OA treated with nanoemulsion gel, nanoemulsion solution, rosemary and peppermint essential oil gel, or diclofenac sodium. Treatments were administered topically at a dose of 1 ml daily. Using behavioral tests, we assessed pain on days 1, 4, 7, and 14 after injection. Finally, we did the histopathological and biochemical evaluation of rats' knee joints.

RESULTS

There were no irritation signs on the animals' skin after receiving the nanoemulsion and no changes in the hematological and biochemical parameters of rats' blood compared to the control group. Receiving nanoemulsion decreased the mechanical (P < 0.001) and thermal allodynia (P < 0.05), thermal hyperalgesia (P < 0.05), and ambulatory-evoked pain in comparison with the OA group. Also, the nanoemulsion receiving rats showed an increase in SOD and GPx activity and a decrease in MDA level. Histopathology of synovial tissues confirmed the results of behavioral and biochemical tests.

CONCLUSION

The nanoemulsion containing essential oils of peppermint and rosemary reduces osteoarthritis pain via increasing antioxidant capacity and improving the histopathological features of the rats' knee joint.

Adrenergic signalling in osteoarthritis

Adrenoceptors (ARs) mediate the effects of the sympathetic neurotransmitters norepinephrine (NE) and epinephrine (E) in the human body and play a central role in physiologic and pathologic processes. Therefore, ARs have long been recognized as targets for therapeutic agents, especially in the field of cardiovascular medicine. During the past decades, the contribution of the sympathetic nervous system (SNS) and particularly of its major peripheral catecholamine NE to the pathogenesis of osteoarthritis (OA) attracted growing interest. OA is the most common degenerative joint disorder worldwide and a disease of the whole joint. It is characterized by progressive degradation of articular cartilage, synovial inflammation, osteophyte formation, and subchondral bone sclerosis mostly resulting in chronic pain. The subchondral bone marrow, the periosteum, the synovium, the vascular meniscus and numerous tendons and ligaments are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers that release NE into the synovial fluid and cells of all abovementioned joint tissues express at least one out of nine AR subtypes. During the past decades, several in vitro studies explored the AR-mediated effects of NE on different cell types in the joint. So far, only a few studies used animal OA models to investigate the contribution of distinct AR subtypes to OA pathogenesis in vivo. This narrative review shortly summarizes the current background knowledge about ARs and their signalling pathways at first. In the second part, we focus on recent findings in the field of NE-induced AR-mediated signalling in different joint tissues during OA pathogenesis and at the end, we will delineate the potential of targeting the adrenergic signalling for OA prevention or treatment. We used the PubMed bibliographic database to search for keywords such as 'joint' or 'cartilage' or 'synovium' or 'bone' and 'osteoarthritis' and/or 'trauma' and 'sympathetic nerve fibers' and/or 'norepinephrine' and 'adrenergic receptors / adrenoceptors' as well as 'adrenergic therapy'.

Crosstalk between skeletal and neural tissues is critical for skeletal health

Emerging evidence in the literature describes a physical and functional association between the neural and skeletal systems that forms a neuro-osteogenic network. This communication between bone cells and neural tissues within the skeleton is important in facilitating bone skeletal growth, homeostasis and repair. The growth and repair of the skeleton is dependent on correct neural innervation for correct skeletal developmental growth and fracture repair, while pathological conditions such as osteoporosis are accelerated by disruptions to sympathetic innervation. To date, different molecular mechanisms have been reported to mediate communication between bone and neural populations. This review highlights the important role of various cell surface receptors, cytokines and associated ligands as potential regulators of skeletal development, homeostasis, and repair, by mediating interactions between the skeletal and nervous systems. Specifically, this review describes how Bone Morphogenetic Proteins (BMPs), Eph/ephrin, Chemokine CXCL12, Calcitonin Gene-related Peptide (CGRP), Netrins, Neurotrophins (NTs), Slit/Robo and the Semaphorins (Semas) contribute to the cross talk between bone cells and peripheral nerves, and the importance of these interactions in maintaining skeletal health.

The effect of exercise therapy on inflammatory activity assessed by MRI in knee osteoarthritis: Secondary outcomes from a randomized controlled trial

OBJECTIVE

This study investigated the effect of exercise therapy on inflammatory activity in synovitis and bone marrow lesions (BMLs) assessed by magnetic resonance imaging (MRI) in patients with knee OA.

METHODS

60 patients with knee OA were randomized 1:1 to 12 weeks of supervised exercise therapy 3 times/week (ET) or a no-attention control group (CG). Synovitis and BMLs were assessed with static MRI with and without contrast and with dynamic contrast enhanced MRI (DCE-MRI). DCE-MRI data was quantified using pixel-by-pixel methodology based on analysis of signal intensity curves. Pain was assessed by the Knee Injury and Osteoarthritis Outcome Score (KOOS). Analyses of covariance were used assessing group differences in changes from baseline to week 12.

RESULTS

33 patients adhered to the protocol and had valid MRI and KOOS data (ET, n = 16, CG, n = 17). Statistically significant and clinically relevant group difference in favour of ET was seen in KOOS pain change (-11.7 points, 95%CI: -20.1 to -3.4). There were statistically significant group differences in DCE-MRI assessed synovitis in the anterior synovium with unchanged inflammatory activity in the ET group compared to the CG. There were no group differences in BMLs and static MRI.

CONCLUSION

Inflammatory activity was unchanged, and pain was reduced in patients with knee OA adhering to 12 weeks of exercise therapy compared to a no-attention control group. The reduction in pain was not explained by changes in inflammatory activity. Overall, the results suggest that exercise is not harmful in knee OA. ClinicalTrials.gov number: NCT01545258.

Adapted protocol of rate of force development and relaxation scaling factor for neuromuscular assessment in patients with knee osteoarthritis

BACKGROUND

The linear relationship between muscle torque and rate of torque rise/relaxation during rapid muscle contractions has been recently introduced as a novel measure of muscle quickness, termed rate of torque development/relaxation scaling factor (RTD-SF/RTR-SF). Because the standard assessment protocol includes potentially painful muscle contractions, the first purpose of this study was to validate an adapted RTD-SF/RTR-SF protocol for knee extensor muscles that utilizes lower submaximal intensities and can be used in knee osteoarthritis patients.

METHODS

A cross-sectional study was performed on a group of healthy controls (n = 24) who underwent the standard RTD-SF/RTR-SF protocol (20-80% of maximum) and the knee osteoarthritis group (n = 24) who underwent the adapted protocol (20-60% of maximum). We calculated the RTD-SF, RTR-SF and the linearity (r²) for both relationships, based on both protocols in controls.

RESULTS

The validity of the adapted protocol was acceptable (intraclass correlation coefficient = 0.77-0.93), with low within-participant variation (coefficient of variability <10%) for both outcome measures. Compared with the control group, the knee osteoarthritis group had similar RTD-SF, but lower linearity of RTD-SF (0.90 vs. 0.82). The RTR-SF (8.0/s vs. 6.7/s) and its linearity (0.87 vs. 0.73) were significantly reduced. Comparing the affected and the unaffected leg in the knee osteoarthritis group, the unaffected leg had greater maximal torque (96.2 vs. 84.1 Nm) and higher linearity for RTD-SF (0.86 vs. 0.80) and RTR-SF (0.82 vs. 0.73).

CONCLUSIONS

We confirmed the validity of the adapted RTD/RTR-SF protocol and its sensitivity to impairments associated with knee osteoarthritis.

The Potential Contribution of Chronic Pain and Common Chronic Pain Conditions to Subsequent Cognitive Decline, New Onset Cognitive Impairment, and Incident Dementia: A Systematic Review and Conceptual Model for Future Research

BACKGROUND

Growing evidence suggests that chronic pain and certain chronic pain conditions may increase risk for cognitive decline and dementia.

OBJECTIVE

In this systematic review, we critically evaluate available evidence regarding the association of chronic pain and specific common chronic pain conditions to subsequent decline in cognitive function, new onset cognitive impairment (CI), and incident Alzheimer's disease and related dementias (ADRD); outline major gaps in the literature; and provide a preliminary conceptual model illustrating potential pathways linking pain to cognitive change.

METHODS

To identify qualifying studies, we searched seven scientific databases and scanned bibliographies of identified articles and relevant review papers. Sixteen studies met our inclusion criteria (2 matched case-control, 10 retrospective cohort, 2 prospective cohort), including 11 regarding the association of osteoarthritis (N = 4), fibromyalgia (N = 1), or headache/migraine (N = 6) to incident ADRD (N = 10) and/or its subtypes (N = 6), and 5 investigating the relation of chronic pain symptoms to subsequent cognitive decline (N = 2), CI (N = 1), and/or ADRD (N = 3).

RESULTS

Studies yielded consistent evidence for a positive association of osteoarthritis and migraines/headaches to incident ADRD; however, findings regarding dementia subtypes were mixed. Emerging evidence also suggests chronic pain symptoms may accelerate cognitive decline and increase risk for memory impairment and ADRD, although findings and measures varied considerably across studies.

CONCLUSION

While existing studies support a link between chronic pain and ADRD risk, conclusions are limited by substantial study heterogeneity, limited investigation of certain pain conditions, and methodological and other concerns characterizing most investigations to date. Additional rigorous, long-term prospective studies are needed to elucidate the effects of chronic pain and specific chronic pain conditions on cognitive decline and conversion to ADRD, and to clarify the influence of potential confounding and mediating factors.

Cutaneous temperature and pressure pain threshold in individuals with knee osteoarthritis

Introduction

Osteoarthritis is a common disease in which skin temperature may be included among the pathophysiological factors. Thermography allows the mapping of cutaneous temperature and may be employed in the investigation of osteoarthritis.

Objectives

To evaluate cutaneous temperature of the lower limbs, as well as to verify its association with pressure pain thresholds in individuals with knee osteoarthritis.

Material and methods

This case series study was conducted with individuals of both genders aged 48–77 years with unilateral knee osteoarthritis. Volunteers underwent thermographic evaluation by an infrared sensor (FLIR T650SC). The anterior region of the thigh and leg and the knee area were evaluated. Pressure pain thresholds (PPT) were evaluated by algometry (Pain Diagnostics, Great Neck, USA) at the vastus medialis, vastus lateralis, rectus femoris, and patellar tendon. Data analysis was conducted with the statistical package SPSS v.24 for Windows. Comparisons between affected and unaffected sides were made by paired Student’s t-test or the Mann-Whitney U test, and associations between variables were assessed by Pearson or Spearman’s correlation coefficient. In all cases, the significance level was set at p ≤ 0.05.

Results

Eleven volunteers (63.1 ±9.5 years) participated in this study. When comparing cutaneous temperature, only the region of the knee showed a significant difference between sides (p = 0.02). There were no differences between affected and unaffected knees regarding pain tolerance (PPT) at all sites evaluated. There were also no significant associations between the study variables.

Conclusions

Individuals with knee osteoarthritis presented a higher temperature of the affected knee, but this was not associated with pressure pain thresholds.

Clinical outcome before and after COVID-19 quarantine in patients affect of knee and hip osteoarthritis

BACKGROUND

The emergency caused by COVID-19 Pandemia has resulted in a complete suspension and consequent delay of common planned surgery such total hip replacement in patients affect by osteoarthritis. At the same time, the issue of the quarantine imposed changes to the normal lifestyle of these patients. The purpose of our study is to evaluate how the presence of these two factors affect the quality of live of patients living in the Italian red zone.

METHODS

From outpatient pre-operative assessment we collect data about: demographic data, WOMAC score, NRS (Numeric rating scale 0-10), PCS SF12 and MCS SF12 score. Selected patients were therefore contacted by telephone call and re-assess using the same score. In addition, patients were asked if they intended to undergo the planned surgery again despite the current emergency Results:  14 patient have been recruited for the study. Male/female ration was 10/4, mean age was 70 years. Pre operative outpatient assessment mean WOMAC score was 44,86 (SD ± 8,52) , mean NRS was 8,07 (SD ± 1,33), PCS SF12 was  30,33 (SD ± 5,0) and MCS SF12 was 40,95 (SD ± 3,51).  At re-evalutation the mean WOMAC score was 32,86 (SD ± 17,88) , mean NRS was 5,79 (SD ± 3,66), PCS SF12 was  39,9 (SD ± 3,70) and MCS SF12 was 50,14 (SD ± 6,86) Conclusion:  The exceptionale pandemic from Covid-19 has profoundly changed our lifestyle, impacting normal daily activities but also on regular surgical activity in patients affected by osteoarthritis. Our study suggested that the lifestyle changes imposed by the situation led to an improvement of clinical score. This shows how an exceptional event can affect many aspects of daily life.

Osteochondral Injury, Management and Tissue Engineering Approaches

Osteochondral lesions (OL) are a common clinical problem for orthopedic surgeons worldwide and are associated with multiple clinical scenarios ranging from trauma to osteonecrosis. OL vary from chondral lesions in that they involve the subchondral bone and chondral surface, making their management more complex than an isolated chondral injury. Subchondral bone involvement allows for a natural healing response from the body as marrow elements are able to come into contact with the defect site. However, this repair is inadequate resulting in fibrous scar tissue. The second differentiating feature of OL is that damage to the subchondral bone has deleterious effects on the mechanical strength and nutritive capabilities to the chondral joint surface. The clinical solution must, therefore, address both the articular cartilage as well as the subchondral bone beneath it to restore and preserve joint health. Both cartilage and subchondral bone have distinctive functional requirements and therefore their physical and biological characteristics are very much dissimilar, yet they must work together as one unit for ideal joint functioning. In the past, the obvious solution was autologous graft transfer, where an osteochondral bone plug was harvested from a non-weight bearing portion of the joint and implanted into the defect site. Allografts have been utilized similarly to eliminate the donor site morbidity associated with autologous techniques and overall results have been good but both techniques have their drawbacks and limitations. Tissue engineering has thus been an attractive option to create multiphasic scaffolds and implants. Biphasic and triphasic implants have been under explored and have both a chondral and subchondral component with an interface between the two to deliver an implant which is biocompatible and emulates the osteochondral unit as a whole. It has been a challenge to develop such implants and many manufacturing techniques have been utilized to bring together two unalike materials and combine them with cellular therapies. We summarize the functions of the osteochondral unit and describe the currently available management techniques under study.

Impacts of Green Tea on Joint and Skeletal Muscle Health: Prospects of Translational Nutrition

Osteoarthritis and sarcopenia are two major joint and skeletal muscle diseases prevalent during aging. Osteoarthritis is a multifactorial progressive degenerative and inflammatory disorder of articular cartilage. Cartilage protection and pain management are the two most important strategies in the management of osteoarthritis. Sarcopenia, a condition of loss of muscle mass and strength, is associated with impaired neuromuscular innervation, the transition of skeletal muscle fiber type, and reduced muscle regenerative capacity. Management of sarcopenia requires addressing both skeletal muscle quantity and quality. Emerging evidence suggests that green tea catechins play an important role in maintaining healthy joints and skeletal muscle. This review covers (i) the prevalence and etiology of osteoarthritis and sarcopenia, such as excessive inflammation and oxidative stress, mitochondrial dysfunction, and reduced autophagy; (ii) the effects of green tea catechins on joint health by downregulating inflammatory signaling mediators, upregulating anabolic mediators, and modulating miRNAs expression, resulting in reduced chondrocyte death, collagen degradation, and cartilage protection; (iii) the effects of green tea catechins on skeletal muscle health via maintaining a dynamic balance between protein synthesis and degradation and boosting the synthesis of mitochondrial energy metabolism, resulting in favorable muscle homeostasis and mitigation of muscle atrophy with aging; and (iv) the current study limitations and future research directions.

Scaffold-Free Cartilage Construct from Infrapatellar Fat Pad Stem Cells for Cartilage Restoration

Once damaged, the articular cartilage has a very limited intrinsic capacity for self-renewal due to its avascular nature. If left untreated, damaged cartilage can lead to progressive degeneration of bone and eventually causes pain. Infrapatellar fat pad adipose-derived mesenchymal stromal cells (IPFP-ASCs) has a potential role for cartilage restoration. However, the therapeutic role for IPFP-ASCs remains to be evaluated in an appropriate osteochondral defect model. Thus, this study aimed to investigate the potential of using a three-dimensional (3D) cartilage construct of IPFP-ASCs as a promising source of cells to restore articular cartilage and to attenuate pain associated with the cartilage defect in an osteochondral defect model. The chondrogenic differentiation potential of the 3D cartilage construct derived from IPFP-ASCs was determined before implantation and postimplantation by gene expression and immunohistochemistry analysis. Pain-related behavior was also assessed by using a weight-bearing test. A significant pain-associated with the osteochondral defect was observed in this model in all groups postinduction; however, this pain can spontaneously resolve within 3 weeks postimplantation regardless of implantation of IPFP-ASCs constructs. The expression of SOX9 and COL2A1 genes in addition to protein expression were strongly expressed in 3D construct IPFP-ASCs. The existence of mature chondrocytes, along with significant (p < 0.05) positive immunostaining for type II collagen and aggrecan, were identified in the implanted site for up to 12 weeks compared with the untreated group, indicating hyaline cartilage regeneration. Taken together, this study demonstrated the successful outcome of osteochondral regeneration with scaffold-free IPFP-ASCs constructs in an osteochondral defect rat model. It provides novel and interesting insights into the current hypothesis that 3D construct IPFP-ASCs may offer potential benefits as an alternative approach to repair the cartilage defect. Impact statement This study provides evidence of using the human 3D scaffold-free infrapatellar fat pad adipose-derived mesenchymal stromal cells (IPFP-ASCs) construct to restore the full-thickness osteochondral defect in a rat model. This study showed that chondrogenic features of the construct could be retained for up to 12 weeks postimplantation. The results of this proof-of-concept study support that human 3D scaffold-free IPFP-ASCs construct has potential benefits in promoting the hyaline-like native cartilage restoration, which may be beneficial as a tissue-specific stem cell for cell-based cartilage therapy. There are several clinical advantages of IPFP-ASC including ease and minimal invasive harvesting, chondrogenic inducible property, and tissue-specific progenitors in the knee.

Randomized clinical trial comparing of transcranial direct current stimulation (tDCS) and transcutaneous electrical nerve stimulation (TENS) in knee osteoarthritis

BACKGROUND

Due to the limitations of pharmacological and surgical management of knee osteoarthritis (OA), several non-pharmacologic approaches including transcutaneous electrical nerve stimulation (TENS) and transcranial direct current stimulation (tDCS) have been introduced, with promising results.

OBJECTIVE

We aimed to investigate and compare the therapeutic effects of TENS and tDCS for the treatment of patients with knee OA.

METHODS

In this double-blinded randomized controlled trial, a total of 40 adult patients with knee OA were randomly allocated to either the TENS or the tDCS group. Patients in either group received 6 sessions of the TENS or tDCS for 2 weeks. Knee strengthening exercises were performed twice daily for the entire treatment period. Patients were evaluated using the visual analogue scale (VAS) and Western Ontario and McMaster Universities (WOMAC).

RESULTS

Significant improvement was observed in all outcomes in both TENS and tDCS groups at each follow up compared to baseline although the early improvement (first follow-up) in the WOMAC index was not significant in the TENS group. Based on the within-subject analysis, the behavior of two treatment groups did not differ regarding the changes in the course of the VAS, WOMAC score and its subscales, i.e. stiffness, pain and function (p = 0.263, 0.051, 0.198, 0.075, and 0.146, respectively).

CONCLUSIONS

Based on the results of this study, the effect of tDCS and TENS was not significantly different on pain and function of patients with knee OA.

Design, Synthesis, and Physicochemical and Pharmacological Profiling of 7-Hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide Derivatives with Antiosteoarthritic Activity In Vivo

The hallmark of joint diseases, such as osteoarthritis (OA), is pain, originating from both inflammatory and neuropathic components, and compounds able to modulate the signal transduction pathways of the cannabinoid type-2 receptor (CB2R) can represent a helpful option in the treatment of OA. In this perspective, a set of 18 cannabinoid type-2 receptor (CB2R) ligands was developed based on an unprecedented structure. With the aim of improving the physicochemical properties of previously reported 4-hydroxy-2-quinolone-3-carboxamides, a structural optimization program led to the discovery of isosteric 7-hydroxy-5-oxopyrazolo[4,3-b]pyridine-6-carboxamide derivatives. These new compounds are endowed with high affinity for the CB2R and moderate to good selectivity over the cannabinoid type-1 receptor (CB1R), associated with good physicochemical characteristics. As to the functional activity at the CB2R, compounds able to act either as agonists or as inverse agonists/antagonists were discovered. Among them, compound 51 emerged as a potent CB2R agonist able to reduce pain in rats carrying OA induced by injection of monoiodoacetic acid (MIA).

Fibrotic changes in the infrapatellar fat pad induce new vessel formation and sensory nerve fiber endings that associate prolonged pain

The infrapatellar fat pad (IFP) contains nerve fiber endings and is considered to play an important role in the perception of knee pain. However, it is unclear whether and to what degree prolonged pain influences the nociceptive role of the IFP. To answer this question, we established a novel rat model of knee pain in which inflammation is restricted to the IFP. Rats received a single intra-IFP injection of monoiodoacetic acid (MIA) (0.2 mg/10 µL or 1.0 mg/10 µL) in the left knee and a phosphate-buffered saline (10 µL) injection in the right knee as a control. Pain-avoidance behavior and histological changes of the knee joint were measured at multiple time points up to 28 days after MIA injection. Histological analysis showed a transient inflammatory response in the IFP body in the 0.2-mg model, whereas prolonged inflammation followed by fibrotic changes was observed in the 1.0-mg model. Subtle histological alterations were observed in the articular cartilage and IFP surface regardless of the dose. The pain-avoidance behavior test indicated the development of prolonged knee pain throughout the experimental period in the 1.0-mg group. Histological assessments showed a significant increase in calcitonin gene-related peptide (CGRP)-positive nerve fiber endings inside IFPs with fibrosis in newly vascularized surrounding regions. These data suggest that irreversible fibrotic changes in the IFP induce the formation of new vessels and CGRP-positive nerve fiber endings that associate prolonged pain in the joint.