Neuropathic pain in the IMI-APPROACH knee osteoarthritis cohort: prevalence and phenotyping

People with osteoarthritis have a higher component of neuropathic pain as compared to those with rheumatoid arthritis: A cross-sectional study

Neuropathic pain may be present in a proportion of patients with osteoarthritis (OA) and rheumatoid arthritis (RA). Its presence may lead to the requirement of altered management approaches in these conditions. This study investigated the prevalence of neuropathic pain in OA as compared to that in RA. Patients with OA and RA were included cross-sectionally if they had no other known neuropathic disorder. The PainDETECT questionnaire was used to assess neuropathic pain. WOMAC and CDAI scores were used to assess disease severity in OA and RA respectively. 69 patients with OA with a mean WOMAC score of 53.30 ± 16.39 and 98 patients with RA with a mean CDAI of 25.48 ± 16.99 were compared. The median PainDETECT score for OA was 13 (0-30) and RA was 5 (0-37) [p<0.001]. 15 patients with OA and six patients with RA were highly likely to have neuropathic pain, while 15 patients with OA and 30 patients with RA were classified as possibly having neuropathic pain. Thus, the proportion of patients free from neuropathic pain was higher in the RA group (63.3%) than in the OA group (39.1%) [p = 0.003]. Both the prevalence and the severity of neuropathic pain were significantly higher in OA than in RA. These findings suggest that neuropathic pain is an important factor in OA, as in RA, and must be considered in management as well as in future research in both these conditions.

Application of the IASP Grading System to Identify Underlying Pain Mechanisms in Patients With Knee Osteoarthritis: A Prospective Cohort Study

OBJECTIVES

This study aimed to apply the International Association for the Study of Pain (IASP) grading system for identifying nociplastic pain in knee osteoarthritis (KOA) awaiting total knee arthroplasty (TKA) and propose criteria to fine-tune decision-making. In addition, the study aimed to characterize a "probable" versus "no or possible" nociplastic pain mechanism using biopsychosocial variables and compare both groups in their 1-year post-TKA response.

METHODS

A secondary analysis of baseline data of a longitudinal prospective study involving 197 patients with KOA awaiting total TKA in Belgium and the Netherlands was performed. Two approaches, one considering 4 and the other 3 pain locations (step 2 of the grading system), were presented. Linear mixed model analyses were performed to compare the probable and no or possible nociplastic pain mechanism groups for several preoperative biopsychosocial-related variables and 1-year postoperative pain. Also, a sensitivity analysis, comparing 3 pain mechanism groups, was performed.

RESULTS

Thirty (15.22%-approach 4 pain locations) and 46 (23.35%-approach 3 pain locations) participants were categorized under probable nociplastic pain. Irrespective of the pain location approach or sensitivity analysis, the probable nociplastic pain group included more woman, was younger, exhibited worse results on various preoperative pain-related and psychological variables, and had more pain 1-year post-TKA compared with the other group.

DISCUSSION

This study proposed additional criteria to fine-tune the grading system for nociplastic pain (except for discrete/regional/multifocal/widespread pain) and characterized a subgroup of patients with KOA with probable nociplastic pain. Future research is warranted for further validation.

Neural and immune roles in osteoarthritis pain: Mechanisms and intervention strategies

Pain is the leading symptom for most individuals with osteoarthritis (OA), a complex condition marked by joint discomfort. Recently, the dynamic interplay between the nervous and immune systems has become a focal point for understanding pain regulation. Despite this, there is still a substantial gap in our comprehensive understanding of the neuroimmune interactions and their effects on pain in OA. This review examines the bidirectional influences between immune cells and nerves in OA progression. It explores current approaches that target neuroimmune pathways, including promoting M2 macrophage polarization and specific neuronal receptor targeting, for effective pain reduction.

Translational potential statement

This review provides a comprehensive overview of the mechanisms underlying the interplay between the immune system and nervous system during the progression of OA, as well as their contributions to pain. Additionally, it compiles existing intervention strategies targeting neuroimmunity for the treatment of OA pain. This information offers valuable insights for researchers seeking to address the challenge of OA pain.

Evaluation and management of knee osteoarthritis

Knee osteoarthritis (KOA) significantly contributes to the global disability burden, with its incidence expected to escalate by 74.9% by 2050. The urgency to comprehend and tackle this condition is critical, necessitating an updated and thorough review of KOA. A systematic review up to February 26, 2024, has elucidated the principal aspects of KOA's pathogenesis, risk factors, clinical manifestations, and contemporary management paradigms. The origins of KOA are intricately linked to mechanical, inflammatory, and metabolic disturbances that impair joint function. Notable risk factors include age, obesity, and previous knee injuries. Diagnosis predominantly relies on clinical assessment, with radiographic evaluation reserved conditionally. The significance of rehabilitation assessments, informed by the International Classification of Functioning, Disability, and Health framework, is highlighted. Treatment strategies are diverse, prioritizing nonpharmacological measures such as patient education, exercise, and weight management, with pharmacological interventions considered adjuncts. Intra-articular injections and surgical options are contemplated for instances where conventional management is inadequate. KOA stands as a predominant disability cause globally, characterized by a complex etiology and profound effects on individuals' quality of life. Early, proactive management focusing on nonpharmacological interventions forms the cornerstone of treatment, aiming to alleviate symptoms and enhance joint function. This comprehensive review underscores the need for early diagnosis, individualized treatment plans, and the integration of rehabilitation assessments to optimize patient outcomes. Further research is needed to refine prevention strategies and improve management outcomes for KOA patients.

Pain Relief, Functional Recovery, and Chondroprotective Effects of Angelica gigas Nakai in Osteoarthritis Due to Its Anti-Inflammatory Property: An In Vitro and In Vivo Study

Osteoarthritis (OA), characterized by chronic pain and joint degradation, is a progressive joint disease primarily induced by age-related systemic inflammation. Angelica gigas Nakai (AG), a medicinal plant widely used in East Asia, exhibits promising results for such conditions. This study aimed to evaluate the potential of AG as a drug candidate for modulating the multifaceted pathology of OA based on its anti-inflammatory properties. We evaluated the efficacy of AG in pain relief, functional improvement, and cartilage erosion delay using monosodium iodoacetate-induced OA rats and acetic acid-induced writhing mice, along with its anti-inflammatory effects on multiple targets in the serum and cartilage of in vivo models and lipopolysaccharide-stimulated RAW 264.7 cells. In vivo experiments demonstrated significant analgesic and chondroprotective effects of AG, along with functional recovery, in model animals compared with the active controls. AG dose-dependently modulated inflammatory OA pathology-related targets, including interleukin-1β, tumor necrosis factor-α, matrix metalloproteinase-13, and cyclooxygenase-2, both in vitro and in vivo. In conclusion, AG could be a potential drug candidate for modulating the multifaceted pathology of OA. Nevertheless, further comprehensive investigations, involving a broader range of compounds, pathologies, and mechanisms, are warranted to validate these findings.

Pain Management Strategies in Osteoarthritis

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 the pathologies of multiple joint tissues. Treatment options are generally classified as pharmacologic, nonpharmacologic, surgical, and complementary and/or alternative, typically used in combination to achieve optimal results. The goals of treatment are the alleviation of symptoms and improvement in functional status. Several studies are exploring various directions for OA pain management, including tissue regeneration techniques, personalized medicine, and targeted drug therapies. The aim of the present narrative review is to extensively describe all the treatments available in the current practice, further describing the most important innovative therapies. Advancements in understanding the molecular and genetic aspects of osteoarthritis may lead to more effective and tailored treatment approaches in the future.

Pain-phenotyping in osteoarthritis: Current concepts, evidence, and considerations towards a comprehensive framework for assessment and treatment

Objectives

Pain as central symptom of osteoarthritis (OA) needs to be addressed as part of successful treatment. The assessment of pain as feature of disease or outcome in clinical practice and drug development remains a challenge due to its multidimensionality and the plethora of confounders. This article aims at providing insights into our understanding of OA pain-phenotypes and suggests a framework for systematic and comprehensive assessments.

Methods

This narrative review is based on a search of current literature for various combinations of the search terms "pain-phenotype" and "knee OA" and summarizes current knowledge on OA pain-phenotypes, putting OA pain and its assessment into perspective of current research efforts.

Results

Pain is a complex phenomenon, not necessarily associated with tissue damage. Various pain-phenotypes have been described in knee OA. Among those, a phenotype with high pain levels not necessarily matching structural changes and a phenotype with low pain levels and impact are relatively consistent. Further subgroups can be differentiated based on patient reported outcome measures, assessments of comorbidities, anxiety and depression, sleep, activity and objective measures such as quantitative sensory testing.

Conclusions

The complexity of both OA as disease and pain in OA prompt the definition of a set of variables that facilitate assessments comparable across studies to maximize our understanding of pain, as central concern for the patient.

Myostatin and CXCL11 promote nervous tissue macrophages to maintain osteoarthritis pain

Pain is the most debilitating symptom of knee osteoarthritis (OA) that can even persist after total knee replacement. The severity and duration of pain do not correlate well with joint tissue alterations, suggesting other mechanisms may drive pain persistence in OA. Previous work identified that macrophages accumulate in the dorsal root ganglia (DRG) containing the somas of sensory neurons innervating the injured knee joint in a mouse OA model and acquire a M1-like phenotype to maintain pain. Here we aimed to unravel the mechanisms that govern DRG macrophage accumulation and programming. The accumulation of F4/80+iNOS+ (M1-like) DRG macrophages was detectable at day 3 after mono-iodoacetate (MIA)-induced OA in the mouse. Depletion of macrophages prior to induction of OA resolved pain-like behaviors by day 7 without affecting the initial development of pain-like behaviors. Analysis of DRG transcript identified CXCL11 and myostatin. CXCL11 and myostatin were increased at 3 weeks post OA induction, with CXCL11 expression partially localized in satellite glial cells and myostatin in sensory neurons. Blocking CXCL11 or myostatin prevented the persistence of OA pain, without affecting the initiation of pain. CXCL11 neutralization reduced the number of total and F4/80+iNOS+ DRG macrophages, whilst myostatin inhibition diminished the programming of F4/80+iNOS+ DRG macrophages. Intrathecal injection of recombinant CXCL11 did not induce pain-associated behaviors. In contrast, intrathecal myostatin increased the number of F4/80+iNOS+ DRG macrophages concurrent with the development of mechanical hypersensitivity that was prevented by macrophages depletion or CXCL11 blockade. Finally, myostatin inhibition during established OA, resolved pain and F4/80+iNOS+ macrophage accumulation in the DRG. In conclusion, DRG macrophages maintain OA pain, but are not required for the induction of OA pain. Myostatin is a key ligand in neuro-immune communication that drives the persistence of pain in OA through nervous tissue macrophages and represent a novel therapeutic target for the treatment of OA pain.

Neuropathic Pain Associated With First Metatarsophalangeal Joint Osteoarthritis: Frequency and Associated Factors

OBJECTIVE

To determine whether neuropathic pain is a feature of first metatarsophalangeal (MTP) joint osteoarthritis (OA).

METHODS

A total of 98 participants (mean ± SD age 57.4 ± 10.3 years) with symptomatic radiographic first MTP joint OA completed the PainDETECT questionnaire (PD-Q), which has 9 questions regarding the intensity and quality of pain. The likelihood of neuropathic pain was determined using established PD-Q cutoff points. Participants with unlikely neuropathic pain were then compared to those with possible/likely neuropathic pain in relation to age, sex, general health (Short Form 12 [SF-12] health survey), psychological well-being (Depression, Anxiety and Stress Scale), pain characteristics (self-efficacy, duration, and severity), foot health (Foot Health Status Questionnaire [FHSQ]), first MTP dorsiflexion range of motion, and radiographic severity. Effect sizes (Cohen's d coefficient) were also calculated.

RESULTS

A total of 30 (31%) participants had possible/likely neuropathic pain (19 possible [19.4%], 11 likely [11.2%]). The most common neuropathic symptoms were sensitivity to pressure (56%), sudden pain attacks/electric shocks (36%) and burning (24%). Compared to those with unlikely neuropathic pain, those with possible/likely neuropathic pain were significantly older (d = 0.59, P = 0.010), had worse SF-12 physical scores (d = 1.10, P < 0.001), pain self-efficacy scores (d = 0.98, P < 0.001), FHSQ pain scores (d = 0.98, P < 0.001), and FHSQ function scores (d = 0.82, P < 0.001), and had higher pain severity at rest (d = 1.01, P < 0.001).

CONCLUSION

A significant proportion of individuals with first MTP joint OA report symptoms suggestive of neuropathic pain, which may partly explain the suboptimal responses to commonly used treatments for this condition. Screening for neuropathic pain may be useful in the selection of targeted interventions and may improve clinical outcomes.

Assessment of Pain in Osteoarthritis of the Knee

Knee osteoarthritis (KOA) pain is a subjective and personal experience, making it challenging to characterise patients' experiences and assess their pain. In addition, there is no global standard for the assessment of pain in KOA. Therefore, this article examines the possible methods of assessing and characterising pain in patients with KOA using clinical symptoms, pain assessment tools, and imaging. We examine the current methods of assessment of pain in KOA and their application in clinical practice and clinical trials. Furthermore, we explore the possibility of creating individualised pain management plans to focus on different pain characteristics. With better evaluation and standardisation of pain assessment in these patients, it is hoped that patients would benefit from improved quality of life. At the same time, improvement in pain assessment would enable better data collection regarding symptom response in clinical trials for the treatment of osteoarthritis.

Joint distraction using a purpose-built device for knee osteoarthritis: a prospective 2-year follow-up

OBJECTIVE

Knee distraction treatment for end-stage osteoarthritis successfully postpones arthroplasty for years. Studies performed thus far used general intended use, patient-personalised or custom-made devices. In this study, for the first time, a device specifically designed for knee distraction is evaluated.

DESIGN

65 patients (≤65 years) with end-stage knee osteoarthritis indicated for arthroplasty received knee distraction. Before, 1-year and 2-year post-treatment, questionnaires were filled out and knee radiographs made. Adverse events and self-reported pain medication were registered.

RESULTS

Forty-nine patients completed 2-year follow-up: one patient did not complete treatment, three patients received arthroplasty in the first and four patients in the second year follow-up. Eight patients were lost to follow-up in the second year. The total Western Ontario and McMaster Universities Osteoarthritis Index score showed a clinically relevant improvement at 1 and 2 years (+26 and +24 points), as did all subscales (all p<0.001). The minimum radiographic joint space width improved over 1 (+0.5 mm; p<0.001) and 2 (+0.4 mm; p=0.015) years, as did the physical Short-Form 36 (+10 points; p<0.001). The most common adverse event was pin tract infection, experienced by 66% of patients, in 88% successfully treated with oral antibiotics. In two cases, hospitalisation and/or intravenous antibiotics were needed. Eight patients experienced device-related complications. None of the complications influenced 2-year outcomes. Before treatment, 42% of patients used pain medication, which had nearly been halved 1 (23%; p=0.02) and 2 years (29%; p=0.27) post-treatment.

CONCLUSIONS

Patients treated with a general applicable, for knee distraction purpose-built device showed, despite adverse events, significant clinical and structural improvement over 2 years.

TRIAL REGISTRATION NUMBER

NL7986.

Discordance between joint pain and imagery severity in the ankle joint and contributors of lower limb activity limitations in adults with haemophilia: A cross-sectional study

INTRODUCTION

People with haemophilia (PwH) suffer from knee and ankle joint pain, but the association with structural damage remains underexplored. They report activity limitations but it is unclear which factors contribute to lower limb activity limitations (LL-AL).

AIMS

This study aimed (i) to analyse the association between ankle joint pain and structure and (ii) explore the contribution of haemophilia-related, individual and psychological factors to LL-AL in PwH.

METHODS

This study included 104 moderate/severe PwH. Ankle pain intensity was assessed with a numeric rating scale and pain sensitivity with algometry (pressure pain threshold (PPT_A )). Ankle structure was assessed with MRI (IPSG-MRI) and ultrasound (HEAD-US), joint health with the Haemophilia Joint Health Score (HJHS). The HAL-LOWCOM subscore evaluated LL-AL. A Spearman correlation analysed the correlation between ankle pain and structure. The contribution of haemophilia-related factors (joint health, overall pain (Brief Pain Inventory-Pain Severity (BPI-PS)), functional status (2-Minute-Walking-Distance, Timed Up and Go); individual factors (age, BMI) and psychological factors (fear and avoidance beliefs over physical activity (FABQ-PA) and work (FABQ-Work), anxiety and depression) to LL-AL was explored using a regression analysis.

RESULTS

Only low correlations were found between ankle pain intensity and structure (IPSG-MRI, HEAD-US). PPT_A was unrelated to structure. Altogether, HJHS, overall pain (BPI-PS), FABQ-Work and age explained 69% of HAL-LOWCOM variance, with 65% explained by the combination of HJHS and BPI-PS.

CONCLUSION

No meaningful associations were found between ankle pain and structural damage, suggesting that other factors may contribute to PwH's ankle pain. In contrast, mainly haemophilia-related factors explained LL-AL variance.

Mitochondria and sensory processing in inflammatory and neuropathic pain

Rheumatic diseases, such as osteoarthritis and rheumatoid arthritis, affect over 750 million people worldwide and contribute to approximately 40% of chronic pain cases. Inflammation and tissue damage contribute to pain in rheumatic diseases, but pain often persists even when inflammation/damage is resolved. Mechanisms that cause this persistent pain are still unclear. Mitochondria are essential for a myriad of cellular processes and regulate neuronal functions. Mitochondrial dysfunction has been implicated in multiple neurological disorders, but its role in sensory processing and pain in rheumatic diseases is relatively unexplored. This review provides a comprehensive understanding of how mitochondrial dysfunction connects inflammation and damage-associated pathways to neuronal sensitization and persistent pain. To provide an overall framework on how mitochondria control pain, we explored recent evidence in inflammatory and neuropathic pain conditions. Mitochondria have intrinsic quality control mechanisms to prevent functional deficits and cellular damage. We will discuss the link between neuronal activity, mitochondrial dysfunction and chronic pain. Lastly, pharmacological strategies aimed at reestablishing mitochondrial functions or boosting mitochondrial dynamics as therapeutic interventions for chronic pain are discussed. The evidence presented in this review shows that mitochondria dysfunction may play a role in rheumatic pain. The dysfunction is not restricted to neuronal cells in the peripheral and central nervous system, but also includes blood cells and cells at the joint level that may affect pain pathways indirectly. Pre-clinical and clinical data suggest that modulation of mitochondrial functions can be used to attenuate or eliminate pain, which could be beneficial for multiple rheumatic diseases.

Biological Targets of Multimolecular Therapies in Middle-Age Osteoarthritis

Knee osteoarthritis (OA) is a common condition, prevalent in middle-agedness, associated with chronic pain and impaired quality of life. Two interrelated biological processes fuel early OA progression: inflammation and structural tissues catabolism. Procatabolic and proinflammatory mediators are interconnected and form part of a self-perpetuating loop. They leverage OA research complexity because of the impossibility to discern certain spatiotemporal tissues' changes from others. Both are shared targets of versatile regenerative multimolecular therapies. In particular, platelet-rich plasma can interfere with inflammation and inflammatory pain. The therapeutic approach is to alter the vicious inflammatory loop by modifying the molecular composition of the synovial fluid, thereby paracrine cellular cross talk. Intra-articular injections of platelet-rich plasma can provide key factors balancing proinflammatory and anti-inflammatory factors, targeting macrophage dysfunction and modulating immune mechanisms within the knee.

Signs Indicative of Central Sensitization Are Present but Not Associated with the Central Sensitization Inventory in Patients with Focal Nerve Injury

Objective: Carpal tunnel syndrome (CTS) is the most common focal nerve injury. People with CTS may show alterations in central processing of nociceptive information. It remains unclear whether the central sensitization inventory (CSI) is capable of detecting such altered central pain processing. Methods: Thirty healthy volunteers were matched with 30 people with unilateral CTS from the orthopaedic waitlist. Changes to central pain processing were established through psychophysical sensory testing (bilateral pressure pain thresholds (PPT), conditioned pain modulation, temporal summation) and pain distribution on body charts. Patients also completed pain severity and function questionnaires, psychological questionnaires and the CSI. Results: Compared to healthy volunteers, patients with CTS have lower PPTs over the carpal tunnel bilaterally (t = −4.06, p < 0.0001 ipsilateral and t = −4.58, p < 0.0001 contralateral) and reduced conditioned pain modulation efficacy (t = −7.31, p <0.0001) but no differences in temporal summation (t = 0.52, p = 0.60). The CSI was not associated with psychophysical measures or pain distributions indicative of altered central pain processing. However, there was a correlation of the CSI with the Beck Depression Inventory (r = 0.426; p = 0.019). Conclusion: Patients with CTS show signs of altered central pain mechanisms. The CSI seems unsuitable to detect changes in central pain processing but is rather associated with psychological factors in people with focal nerve injuries.