Evidence for central sensitization in patients with osteoarthritis pain: A systematic literature review

Do tender joints in active psoriatic arthritis reflect inflammation assessed by ultrasound and magnetic resonance imaging?

OBJECTIVE

To investigate the association between clinical joint tenderness and intra- and periarticular inflammation as assessed by ultrasound and magnetic resonance imaging (MRI) in patients with active psoriatic arthritis (PsA) and to explore if the associations differ according to patient-reported outcomes (PROs) and structural damage.

METHODS

Forty-one patients with active PsA and hand involvement had 76/78 joints examined for swelling/tenderness and ultrasound and MRI of 24 and 12 finger joints, respectively. Synovitis, tenosynovitis, periarticular inflammation and erosions were assessed using OMERACT definitions and scoring systems. Correlation between imaging inflammation sum-scores (intra-and periarticular) and tender/swollen joint counts were calculated using Spearman's rho, agreement at joint level was examined using prevalence and bias adjusted kappa (PABAK). Subgroup analyses explored the influence of PROs and radiographic erosive disease on these associations.

RESULTS

No significant correlations were found between tender or swollen joint counts and imaging inflammation sum-scores (rho=-0.31-0.38). In patients with higher level of overall pain, disability and lower self-reported mental health, a tendency towards negative correlations were found. At joint level, intra- and periarticular imaging inflammatory lesions had slight agreement with joint tenderness (PABAK=0.02-0.19) and slight to moderate with swelling (PABAK=0.16-0.54). For tender joints, agreement with imaging inflammation was even weaker in patients with either high overall pain scores, high disability scores, and/or non-erosive disease.

CONCLUSION

Joint tenderness had low association with imaging signs of inflammation in PsA patients, particularly in patients with high self-reported pain, disability and low mental health, indicating that tenderness is influenced by other parameters than local inflammation.

Peripheral pain mechanisms in osteoarthritis

There is a well-established historical observation that structural joint damage by plain X-ray correlates poorly with symptomatic disease in osteoarthritis (OA). This is often attributed to the inability to visualise soft-tissue pathology within the joint and the recognition of heterogeneous patient factors that drive central pain sensitisation. A major issue is the relative paucity of mechanistic studies in which molecular pathogenesis of pain is interrogated in relation to tissue pathology. Nonetheless, in recent years, three broad approaches have been deployed to attempt to address this: correlative clinical studies of peripheral and central pain outcomes using magnetic resonance imaging, where soft-tissue processes can be visualised; molecular studies on tissue from patients with OA; and careful molecular interrogation of preclinical models of OA across the disease time course. Studies have taken advantage of established clinical molecular targets such as nerve growth factor. Not only is the regulation of nerve growth factor within the joint being used to explore the relationship between tissue pathology and the origins of pain in OA, but it also provides a core model on which other molecules present within the joint can modulate the pain response. In this narrative review, how molecular and pathological tissue change relates to joint pain in OA will be discussed. Finally, a model for how tissue damage may lead to pain over the disease course will be proposed.

Combination of Pain Location and Pain Duration is Associated with Central Sensitization-Related Symptoms in Patients with Musculoskeletal Disorders: A Cross-Sectional Study

OBJECTIVES

Increased evidence indicates that pain location affects central sensitization (CS)-related symptoms. In addition, pain location and pain duration may be intricately related to CS-related symptoms. However, these factors have been investigated separately. This study aimed to investigate the association between CS-related symptoms and pain location and/or pain duration in patients with musculoskeletal disorders.

METHODS

Six hundred thirty-five participants with musculoskeletal disorders were included in this cross-sectional study. All participants were assessed for pain location, pain duration, central sensitization inventory (CSI), EuroQol-5 dimension, and brief pain inventory. The participants were categorized into 3 groups based on pain location (spinal, limb, and both spinal and limb pain) and into 2 groups based on pain duration (acute and chronic pain).

RESULTS

The interaction between pain location and pain duration were not significant on CSI score (P > 0.05). The odds ratio for higher CSI score (≥ 40) in patients with both spinal and limb pain vs. those with spinal or limb pain was 2.64 (P < 0.01) and that in patients with chronic pain vs. those with acute pain was 1.31 (P = 0.52). In addition, the prevalence of higher CSI scores in the combination of chronic and "both spinal and limb" pain was high (23.1%, adjusted residual = 4.48).

CONCLUSIONS

Pain location independently influenced CSI scores, and the combination of both spinal and limb pain and chronic pain indicated high CSI scores. The combination of pain location and pain duration is an important clue that points to CS-related symptoms.

Methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system: a systematic review

ABSTRACT

Mechanism-based classification of pain has been advocated widely to aid tailoring of interventions for individuals experiencing persistent musculoskeletal pain. Three pain mechanism categories (PMCs) are defined by the International Association for the Study of Pain: nociceptive, neuropathic, and nociplastic pain. Discrimination between them remains challenging. This study aimed to build on a framework developed to converge the diverse literature of PMCs to systematically review methods purported to discriminate between them; synthesise and thematically analyse these methods to identify the convergence and divergence of opinion; and report validation, psychometric properties, and strengths/weaknesses of these methods. The search strategy identified articles discussing methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system. Studies that assessed the validity of methods to discriminate between categories were assessed for quality. Extraction and thematic analysis were undertaken on 184 articles. Data synthesis identified 200 methods in 5 themes: clinical examination, quantitative sensory testing, imaging, diagnostic and laboratory testing, and pain-type questionnaires. Few methods have been validated for discrimination between PMCs. There was general convergence but some disagreement regarding findings that discriminate between PMCs. A combination of features and methods, rather than a single method, was generally recommended to discriminate between PMCs. Two major limitations were identified: an overlap of findings of methods between categories due to mixed presentations and many methods considered discrimination between 2 PMCs but not others. The results of this review provide a foundation to refine methods to differentiate mechanisms for musculoskeletal pain.

Basic Mechanisms of Pain in Osteoarthritis: Experimental Observations and New Perspectives

The specific changes in the peripheral neuronal pathways underlying joint pain in osteoarthritis are the focus of this review. The plasticity of the nociceptive system in osteoarthritis and how this involves changes in the structural, physiologic, and genetic properties of neurons in pain pathways are discussed. The role of the neurotrophin, nerve growth factor, in these pathogenic processes is discussed. Finally, how neuronal pathways are modified by interaction with the degenerating joint tissues they innervate and with the innate immune system is considered. These extensive cellular interactions provide a substrate for identification of targets for osteoarthritis pain.

Neuroimmune interactions and osteoarthritis pain: focus on macrophages

Bidirectional interactions between the immune system and the nervous system are increasingly appreciated as playing a pathogenic role in chronic pain. Unraveling the mechanisms by which inflammatory pain is mediated through communication between nerves and immune cells may lead to exciting new strategies for therapeutic intervention. In this narrative review, we focus on the role of macrophages in the pathogenesis of osteoarthritis (OA) pain. From regulating homeostasis to conducting phagocytosis, and from inducing inflammation to resolving it, macrophages are plastic cells that are highly adaptable to their environment. They rely on communicating with the environment through cytokines, growth factors, neuropeptides, and other signals to respond to inflammation or injury. The contribution of macrophages to OA joint damage has garnered much attention in recent years. Here, we discuss how macrophages may participate in the initiation and maintenance of pain in OA. We aim to summarize what is currently known about macrophages in OA pain and identify important gaps in the field to fuel future investigations.

Motor cortex transcranial direct current stimulation effects on knee osteoarthritis pain in elderly subjects with dysfunctional descending pain inhibitory system: A randomized controlled trial

BACKGROUND

Although evidence has indicated a positive effect of transcranial direct current stimulation (tDCS) on reducing pain, few studies have focused on the elderly population with knee osteoarthritis (KOA).

OBJECTIVE

To evaluate whether tDCS reduces KOA pain in elderly individuals with a dysfunctional descending pain inhibitory system (DPIS).

METHODS

In a double-blind trial, individuals ≥ 60 years with KOA pain and a dysfunctional DPIS, we randomly assigned patients to receive 15 daily sessions of 2 mA tDCS over the primary motor cortex (anode) and contralateral supraorbital area (cathode) (M1-SO) for 20 min or sham tDCS. Change in pain perception indexed by the Brief Pain Inventory (BPI) at the end of intervention was the primary outcome. Secondary outcomes included: disability, quantitative sensory testing, pain pressure threshold and conditioned pain modulation (CPM). Subjects were followed-up for 2 months.

RESULTS

Of the 104 enrolled subjects, with mean (SD) age of 73.9 (8.01) years and 88 (84.6%) female, 102 finished the trial. In the intention-to-treat analysis, the active tDCS group had a significantly greater reduction in BPI compared to the sham group (difference, 1.59; 95% CI, 0.95 to 2.23; P < 0.001; Cohen's d, 0.58); and, also a significantly greater improvement in CPM-pressure in the knee (P = 0.01) and CPM-pain in the hand (P = 0.01). These effects were not sustained at follow-up. The intervention was well tolerated, with no severe adverse effects.

CONCLUSION

M1-SO tDCS is associated with a moderate effect size in reducing pain in elderly patients with KOA after 15 daily sessions of stimulation. This intervention has also shown to modulate the DPIS.

Diagnostic accuracy of the clinical indicators to identify central sensitization pain in patients with musculoskeletal pain

Background

The identification of central sensitization (CS) is an important aspect in the management of patients with chronic musculoskeletal pain. Several methods have been developed, including clinical indicators and psychophysical measures. However, whether clinical indicators coincide with the psychophysical test of CS-related sign and symptoms is still unknown. Therefore, the present study aimed to analyze the diagnostic accuracy of the clinical indicators in identifying CS-related sign and symptoms in patients with musculoskeletal pain.

Methods

One-hundred consecutive patients with musculoskeletal pain were included. Clinical indicators (index method) based on a combination of patient self-report pain characteristics and physical examination were used to identify the phenotype of patients with musculoskeletal pain and the predominance of the CS-related sign and symptoms. Conditioned pain modulation (CPM) was assessed by the Cold Pressor Test (reference standard), which is a psychophysical test used to detect impairment of CPM. Measurements of the diagnostic accuracy were performed.

Results

Twenty-seven patients presented predominance of CS-related sign and symptoms in the assessment of the clinical indicators, and 20 had impairment of CPM. Clinical indicators showed high accuracy (75.0%; 95% confidence interval = 65.3 to 83.1), high specificity (80.0%; 95% confidence interval = 69.6 to 88.1), high negative predictive value (87.7%; 95% confidence interval = 81.2 to 92.1), and a relevant positive likelihood ratio (2.8, 95% confidence interval = 1.5 to 5.0) when compared to the Cold Pressor Test.

Conclusion

Clinical indicators demonstrated a valuable tool for detecting the impaired CPM, which is a remarkable feature of the CS-related sign and symptoms. Clinicians are encouraged to use the clinical indicators in the management of patients with musculoskeletal pain.

Quantitative Sensory Testing Protocols to Evaluate Central and Peripheral Sensitization in Knee OA: A Protocol for a Scoping Review

BACKGROUND

Quantitative sensory testing (QST) methods have become widely used for the assessment of nervous system sensitization to nociceptive signalling in studies of people with knee osteoarthritis (OA). However, few standardised QST protocols have been developed. Variability in their execution may lead to differences in their interpretation.

OBJECTIVE

The proposed scoping review will seek to identify various QST methodologies being used in the assessment of sensitization and how sensitization is being defined in people with knee OA. Methods and Analysis: This scoping review will be guided by existing scoping review methodologies. Relevant studies will be extracted from the following electronic databases: Medical Literature Analysis and Retrieval System Online, ExcerptaMedica Database, Allied and Complementary Medicine Database and the Cumulative Index to Nursing Allied Health Literature. Independent screening of the abstracts and full articles and data extraction will be performed in pairs. Information extracted will focus on qualitative and quantitative data relevant to the content of the protocols from included studies. Data will be summarised in order to draw conclusions on the common elements used in QST protocols and definitions of sensitization for knee OA.

CONCLUSION

This scoping review will provide insight into the most common methods of QST used in the assessment of nociceptive signaling in people with knee OA. This will potentially identify areas where a systematic review or other primary research may be required in order to develop fixed evidence-based protocols for QST in patients with knee OA.

Pain characteristics and biomarkers in treatment approaches for osteoarthritis pain

Osteoarthritis (OA) is a progressive disease and OA pain intensity is related to ongoing pathophysiological changes. However, OA pain is complex and multimodal; its characteristics, including severity, localization and the stimuli that elicit it, can change as the disease progresses and differ greatly among patients. Understanding mechanisms underlying specific pain characteristics may help guide clinicians in choosing appropriate treatments, targeting treatments to those patients most likely to benefit. Associations have been demonstrated between biomarkers and some characteristics of OA pain, and to processes linked to the shift in pain characteristics over the course of OA. This article examines how understanding OA pain characteristics and their relation to the disease process could inform treatment choice when applying well-established treatment guidelines.

Risk factors of pain, physical function, and health-related quality of life in elderly people with knee osteoarthritis: A cross-sectional study

Data on the precise mechanisms of the complex interactions of factors related to clinical impact of knee osteoarthritis (KOA) in the elderly population remain limited. To find predictors that explain pain intensity, physical function, and quality of life in elderly KOA subjects, we performed a cross-sectional analysis of the baseline data from a randomized trial. The trial included 104 subjects (aged ≥60) with KOA pain and dysfunctional endogenous pain-inhibitory system activity assessed by conditioned pain modulation (CPM). Three multiple linear regression models were performed to understand the independent predictors of Brief Pain Inventory (BPI), WOMAC function subscale (WOMACFunc), and SF-12 physical subscale (SF12-PCS). Model 1 showed that BPI pain score was predicted by low CPM response, high von-Frey light touch threshold, worse radiological severity as indexed by Kellgren-Lawrence grade (KL), high von-Frey punctate pain intensity and high levels of anxiety (adjusted R2 = 27.1%, F (6,95) = 7.27, P < 0.0001). In model 2, von-Frey light touch threshold, KL, depressive symptoms indexed by Beck Depression Inventory (BDI), level of sleepiness and pain pressure threshold were risk factors for SF12-PCS (adjusted R2 = 31.9%, F (5,96) = 10.5, P < 0.0001). Finally, model 3 showed that WOMACFunc was predicted by BDI, KL and BPI (adjusted R2 = 41%, F (3,98) = 24.42, P < 0.0001). Our data provides an interesting framework to understand the predictors of KOA pain in the elderly and highlights how its related outcomes are affected by disease-specific factors, somatosensory dysfunction and emotional factors.

Assessment of diagnostic criteria for the identification of central sensitization in patients with osteoarthritis pain: Results from a Delphi survey

To assess diagnostic criteria and currently used tools for the identification of central sensitization (CS) in patients with joint pain due to osteoarthritis (OA).Qualitative, cross-sectional and multicenter study based on a 2-round Delphi surveyPublic and private medical centers attending patients with joint pain.A total of 113 specialists in traumatology, physical medicine and rehabilitation, pain management, rheumatology, primary care physicians and geriatrics were enrolled in the study.Participants completed an ad-hoc 26-item questionnaire available from a microsite in Internet.The questionnaire was divided into 6 sections with general data on CS, impact of CS in patients with knee osteoarthritis (KOA), diagnostic criteria for CS, non-pharmacological and pharmacological treatment of CS and usefulness of the concept of CS in the integral management of patients with KOA. Consensus was defined as 75% agreement.Diagnostic criteria included pain of disproportionate intensity to the radiological joint lesion (agreement 86.7%), poor response to usual analgesics (85.8%), progression of pain outside the site of the lesion (76.1%) and concurrent anxiety and depression (76.1%). Based on the opinion of the specialists, about 61% of patients with KOA present moderate-to-severe pain, 50% of them show poor response to conventional analgesics, and 40% poor clinical-radiological correlation. Patients with KOA and CS showed higher functional disability and impairment of quality of life than those without CS (88.5%) and have a poor prognosis of medical, rehabilitation and surgical treatment (86.7%). Early diagnosis and treatment of CS may preserve function and quality of life during all steps of the disease (90.3%).The management of patients with osteoarthritis pain and CS requires the consideration of the intensity of pain related to the joint lesion, response to analgesics, progression of pain to other areas and concurrent anxiety and depression to establish an adequate therapeutic approach based on diagnostic criteria of CS.

Intra-articular collagenase in the spinal facet joint induces pain, DRG neuron dysregulation and increased MMP-1 absent evidence of joint destruction

Degeneration is a hallmark of painful joint disease and is mediated by many proteases that degrade joint tissues, including collagenases. We hypothesized that purified bacterial collagenase would initiate nociceptive cascades in the joint by degrading the capsular ligament's matrix and activating innervating pain fibers. Intra-articular collagenase in the rat facet joint was investigated for its effects on behavioral sensitivity, joint degeneration, and nociceptive pathways in the peripheral and central nervous systems. In parallel, a co-culture collagen gel model of the ligament was used to evaluate effects of collagenase on microscale changes to the collagen fibers and embedded neurons. Collagenase induced sensitivity within one day, lasting for 3 weeks (p < 0.001) but did not alter ligament structure, cartilage health, or chondrocyte homeostasis. Yet, nociceptive mediators were increased in the periphery (substance P, pERK, and MMP-1; p ≤ 0.039) and spinal cord (substance P and MMP-1; p ≤ 0.041). The collagen loss (p = 0.008) induced by exposing co-cultures to collagenase was accompanied by altered neuronal activity (p = 0.002) and elevated neuronal MMP-1 (p < 0.001), suggesting microscale collagen degradation mediates sensitivity in vivo. The induction of sustained sensitivity and nociception without joint damage may explain the clinical disconnect in which symptomatic joint pain patients present without radiographic evidence of joint destruction.

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.

Identifying participants with knee osteoarthritis likely to benefit from physical therapy education and exercise: A hypothesis-generating study

BACKGROUND

The purpose of this investigation was to undertake a hypothesis-generating study to identify candidate variables that characterize people with knee osteoarthritis who are most likely to experience a positive response to exercise.

METHODS

One hundred and fifty participants with knee osteoarthritis participated in this observational, longitudinal study. All participants received a standard exercise intervention that consisted of 20-min sessions two to three times a week for three months. The classification and regression tree methodology (CART) was used to develop prediction of positive clinical outcome. Positive pain and disability outcomes (dependent variables) were defined as an improvement in pain intensity by >50% or an improvement of five or more on the Oxford knee score, respectively. The predictor variables considered included age, sex, body mass index, knee osteoarthritis severity (Kellgren/Lawrence grade), pain duration, use of medication, range of knee motion, pain catastrophizing, self-efficacy and knee self-perception.

RESULTS

Fifty-five participants (36.6%) were classified as responders for pain intensity and 36.6% were classified as responders for disability. The CART model identified impairments in knee self-perception and knee osteoarthritis severity as the discriminators for pain intensity reduction following exercise. No variables predicted reduction of disability level following exercise.

CONCLUSIONS

Such findings suggest that both body perception and osteoarthritis severity may play a role in treatment outcome with exercise. It also raises the possibility that those with higher levels of disrupted body perception may need additional treatment targeted at restoring body perception prior to undertaking exercise.

SIGNIFICANCE

Regardless age, sex, body mass index, pain duration, use of medication, knee range of motion, pain catastrophizing and self-efficacy, participants with knee osteoarthritis who report low levels of body perception disruption (a FreKAQ score ≦ 17) and minimal structural changes (KL grade I) demonstrate significantly better outcomes from exercise therapy than other participants.

Symptoms of central sensitization in patients with inflammatory bowel diseases: a case-control study examining the role of musculoskeletal pain and psychological factors

OBJECTIVES

Musculoskeletal (MSK) pain is a common complaint in patients with inflammatory bowel diseases (IBD). MSK pain in IBD has previously demonstrated association with symptoms of central sensitization; however it is uncertain whether these symptoms are influenced simply by the presence of MSK pain and/or IBD. Primary aim of this study was to investigate whether symptoms of central sensitization differed across three groups: IBD patients with and without MSK pain and healthy controls. Secondary aim was to investigate between-group differences for measures of somatosensory functioning.

METHODS

Cross-sectional study was performed on adults with IBD. Assessments included: central sensitization inventory (CSI), pressure pain threshold, temporal summation, conditioned pain modulation, perceived stress, affect style, anxiety, depression, and pain catastrophizing. One-way analyses of variance and covariance were used to investigate between-group differences for measures of central sensitization and potential confounding by psychological factors.

RESULTS

Study participants (n=66) were age/gender matched across three study groups. Between-group differences were solely demonstrated for CSI scores [F(2,63)=19.835, p<0.001, r=0.62], with IBD patients with MSK pain demonstrating the highest CSI scores and healthy controls the lowest. After controlling for individual psychological features, post hoc comparisons indicated that CSI scores were significantly different between-groups (p≤0.025) after controlling for most psychological variables, with the exception of perceived stress (p=0.063) and pain catastrophizing (p=0.593).

CONCLUSIONS

IBD patients as a whole demonstrated significantly greater symptoms of central sensitization compared to healthy controls. However, IBD patients with persistent MSK pain demonstrated the greatest symptoms of central sensitization compared to patients without MSK pain and healthy controls. Between-group differences for CSI in IBD patients with MSK were not confounded by psychological features.

IMPLICATIONS

Study results indicate that persistent MSK pain in IBD represents patients with greater central sensitization symptomology. This increased symptomology is suggestive of underlying mechanisms related to central sensitization, highlighting patient potentially at risk for worse pain experiences.

A Review of Non-Surgical Pain Management in Osteoarthritis

Osteoarthritis is a prominent cause of disability in older adults, especially with an increasingly obese and aging population. Clinical management of pain secondary to osteoarthritis should focus on education and self-management with exercise and weight management as a priority. Surgical intervention should only be considered once conservative measures have failed. This review provides a clinical update on the pathogenesis, diagnosis, and management of osteoarthritis.

Nociceptive mechanisms driving pain in a post-traumatic osteoarthritis mouse model

In osteoarthritis (OA), pain is the dominant clinical symptom, yet the therapeutic approaches remain inadequate. The knowledge of the nociceptive mechanisms in OA, which will allow to develop effective therapies for OA pain, is of utmost need. In this study, we investigated the nociceptive mechanisms involved in post-traumatic OA pain, using the destabilization of the medial meniscus (DMM) mouse model. Our results revealed the development of peripheral pain sensitization, reflected by augmented mechanical allodynia. Along with the development of pain behaviour, we observed an increase in the expression of calcitonin gene-related peptide (CGRP) in both the sensory nerve fibers of the periosteum and the dorsal root ganglia. Interestingly, we also observed that other nociceptive mechanisms commonly described in non-traumatic OA phenotypes, such as infiltration of the synovium by immune cells, neuropathic mechanisms and also central sensitization were not present. Overall, our results suggest that CGRP in the sensory nervous system is underlying the peripheral sensitization observed after traumatic knee injury in the DMM model, highlighting the CGRP as a putative therapeutic target to treat pain in post-traumatic OA. Moreover, our findings suggest that the nociceptive mechanisms involved in driving pain in post-traumatic OA are considerably different from those in non-traumatic OA.

Central sensitization inventory scores correlate with pain at rest in patients with hip osteoarthritis: a retrospective study

Background

Patients with persistent pain due to osteoarthritis (OA) complain of multiple symptoms that cannot be explained solely by structural changes. A poor correlation exists between structural and inflammatory changes in OA and pain levels. Central sensitization (CS) has been identified as a factor that induces chronic pain in patients with OA. Although it is important to identify osteoarthritis patients with CS components, the prevalence and characteristics of CS, especially those in patients with hip OA, are not well understood. Thus, we aimed to determine the prevalence and characteristics of CS in patients with hip OA, in this study.

Methods

The CS Inventory (CSI), used as a non-invasive routine clinical tool to evaluate the presence of CS 1 month before surgery in 100 patients with hip OA, was measured at our outpatient clinic, and the data were retrospectively reviewed. We determined the number of patients with a CSI score of 40 points or higher and assessed the relationships between the CSI score and clinical factors (including age, duration of hip pain, degree pain at rest and on activity, by using the visual analogue scale [VAS] and the Harris Hip Score) using the Spearman’s correlation coefficient.

Results

The mean age of participants was 63.9 ± 11.6 years, and there were 15 men and 85 women. All patients had hip OA, categorised as advanced and terminal stage (Tönnis grade 2–3) on preoperative plain radiography. The mean duration of hip pain was 4.2 ± 4.4 years. The mean CSI score was 19.5 ± 11.3 and 5 (5.0%) of the patients had a score of 40 or more points. CSI scores correlated significantly only with VAS pain at rest (r = 0.348, P < 0.001).

Conclusion

In this study, 1 out of every 20 hip OA patients had CS components. CSI scores were significantly correlated with pain at rest in hip OApatients. CS approaches to hip OA may be one of the treatment options for pain at rest.

Association between chronic pain and pre-frailty in Japanese community-dwelling older adults: A cross-sectional study

A relationship between chronic pain and frailty has been reported. The early detection and prevention of frailty are recommended, in part because community-dwelling older adults in a pre-frailty state may return to a healthy state. The relationship between chronic pain and pre-frailty is not known. Toward the goal of promoting a reversible return to health from pre-frailty, we investigated the relationship between chronic pain and pre-frailty among community-dwelling older adults. We assessed the frailty and chronic pain of 107 older adults who were participating in community health checks. The status of physical frailty was based on the five components described by Fried (2001): muscle weakness shown by handgrip strength, slowness of gait speed, weight loss, low physical activity, and exhaustion. Chronic pain was assessed based on pain intensity, the Pain Catastrophizing Scale (PCS), the Japanese version of the Geriatric Depression Scale-15 (GDS-15), and the Central Sensitization Inventory (CSI). The prevalence of chronic pain with pre-frailty was 40.2%. A hierarchical analysis revealed that PCS-measured helplessness (odds ratio [OR]: 0.88) and the CSI (OR: 0.87) were significant factors associated with the presence of chronic pain with pre-frailty. The prevalence of chronic pain with pre-frailty was high, and chronic pain and pre-frailty were strongly related. New intervention or prevention programs that take into account both chronic pain and pre-frailty must be created as soon as possible.

Prevalence of Myofascial Trigger Points in Patients with Mild to Moderate Painful Knee Osteoarthritis: A Secondary Analysis

OBJECTIVE

To determine the prevalence of myofascial trigger points (MTrPs) and the correlation between the number of MTrPs and pain and function in patients presenting knee pain osteoarthritis (OA).

METHODS

This was a secondary analysis of data from a cross-sectional study. The prevalence of MTrPs located in tensor fasciae latae, hip adductors, hamstrings, quadriceps, gastrocnemius, and popliteus muscles was studied in 114 patients (71 men and 43 women) with knee OA. Pain and functionality were assessed with a numerical pain rating scale (NPRS), the Western Ontario, McMaster Universities Osteoarthritis Index (WOMAC) score, the Barthel Index, and the timed up and go test.

RESULTS

The prevalence of latent MTrPs was detected via palpation and was estimated to be 50%, 35%, 25%, 29%, 33%, and 12% for tensor fasciae latae, hip adductors, hamstrings, quadriceps, gastrocnemius, and popliteus muscles, respectively. The prevalence of active MTrPs was estimated to be 11%, 17%, 30%, 18%, 25%, and 17% for tensor fasciae latae, hip adductors, hamstrings, quadriceps, gastrocnemius, and popliteus muscles, respectively. Pain was measured with the NPRS scale and was poorly correlated with the prevalence of latent MTrPs (r = 0.2; p = 0.03) and active MTrPs (r = 0.23; p = 0.01) in the hamstrings. Disability was moderately correlated with the number of latent MTrPs in the tensor fasciae latae muscle (Barthel, r = 0.26; p = 0.01 and WOMAC, r = 0.19; p = 0.04).

CONCLUSIONS

This secondary analysis found that the prevalence of the MTrPs varied from 11% to 50% in different muscles of patients with mild to moderate painful knee osteoarthritis. Pain was correlated poorly with the prevalence of latent and active MTrPs in the hamstring muscles, and disability correlated moderately with the number of latent MTrPs in tensor fasciae latae.

Relationships Between Psychological, Sleep, and Physical Activity Measures and Somatosensory Function in People With Peripheral Joint Pain: A Systematic Review and Meta-Analysis

OBJECTIVE

Alteration in somatosensory function has been linked to pain experience in individuals with joint pain. In this systematic review we aimed to establish the level of evidence of associations between psychological, social, physical activity, and sleep measures and somatosensory function that were assessed via quantitative sensory testing (QST) among individuals with joint pain.

METHODS

A comprehensive literature search was conducted in 6 electronic databases from their inception to July 2019. Two reviewers independently assessed the methodological quality using a modified Quality in Prognostic Studies (QUIPS) tool and supplemented with recommendations from the Critical Appraisal and Data Extraction for Systematic Review of Prediction Modelling Studies (CHARMS) checklist and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. The level of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. Data were pooled to evaluate the strength of the relationships of interest.

RESULTS

Seventeen studies related to joint pain were included. Pain catastrophizing, depression, anxiety, and physical activity level have been shown to have a significant (small to fair) association with several QST measures. Pressure pain threshold (PPT) is the only measure that was found to be consistently correlated with all the domains. The overall quality of evidence for all factors ranged from very low to moderate. Subgroup analysis revealed a stronger association for depression and pain catastrophizing and PPT and temporal pain summation in individuals with shoulder pain.

CONCLUSION

Psychological factors and physical activity levels are associated with somatosensory function in people with joint pain. These factors need to be adjusted when establishing predictive relationships between somatosensory function and pain outcomes in individuals with joint pain.

Nutritional intervention in chronic pain: an innovative way of targeting central nervous system sensitization?

INTRODUCTION

Few treatment programs for chronic pain nowadays take a dietary pattern or adipose status into account.

AREAS COVERED

An important role of neuroinflammation in chronic pain is now well established, at least in part due to increased central nervous system glial activation. Based on preclinical studies, it is postulated that the interaction between nutrition and central sensitization is mediated via bidirectional gut-brain interactions. This model of diet-induced neuroinflammation and consequent central sensitization generates a rationale for developing innovative treatments for patients with chronic pain. Methods: An umbrella approach to cover the authors' expert opinion within an evidence-based viewpoint.

EXPERT OPINION

A low-saturated fat and low-added sugar dietary pattern potentially decreases oxidative stress, preventing Toll-like receptor activation and subsequent glial activation. A low-saturated fat and low-added sugar diet might also prevent afferent vagal nerve fibers sensing the pro-inflammatory mediators that come along with a high-(saturated) fat or energy-dense dietary pattern, thereby preventing them to signal peripheral inflammatory status to the brain. In addition, the gut microbiota produces polyamines, which hold the capacity to excite N-methyl-D-aspartate receptors, an essential component of the central nervous system sensitization. Hence, a diet reducing polyamine production by the gut microbiota requires exploration as a therapeutic target for cancer-related and non-cancer chronic pain.

Behavioral Graded Activity+ (BGA+) for Osteoarthritis: A Paradigm Shift from Disease-Based Treatment to Personalized Activity Self-Management

Three promising directions for improving care for osteoarthritis (OA) include novel education strategies to target unhelpful illness and treatment beliefs; methods to enhance the efficacy of exercise interventions; and innovative, brain-directed treatments. Here we explain that each of those three promising directions can be combined through a paradigm-shift from disease-based treatments to personalized activity self-management for patients with OA. Behavioral graded activity (BGA) accounts for the current understanding of OA and OA pain and allows a paradigm shift from a disease-based treatment to personalized activity self-management for patients with OA. To account for the implementation barriers of BGA, we propose adding pain neuroscience education to BGA (referred to as BGA⁺). Rather than focusing on the biomedical (and biomechanical) disease characteristics of OA, pain neuroscience education implies teaching people about the underlying biopsychosocial mechanisms of pain. To account for the lack of studies showing that BGA is “safe” with respect to disease activity and the inflammatory nature of OA patients, a trial exploring the effects of BGA⁺ on the markers of inflammation is needed. Such a trial could clear the path for the required paradigm shift in the management of OA (pain) and would allow workforce capacity building that de-emphasizes biomedical management for OA.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an opioid characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action, since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol limits the risk of opioid-related adverse events, such as gastrointestinal disturbances. Moreover, the NA component becomes predominant, at least, in some types of pain, with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of severe uncontrolled chronic pain characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an analgesic molecule characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol has two important consequences: first, it limits the risk of opioid-related adverse events, as well as the risk of dependence; second, the NA component becomes predominant at least in some types of pain with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of chronic pain conditions characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

What is the selection process for osteoarthritis pharmacotherapy?

Osteoarthritis is the most prevalent joint condition that continues to increase with an ever-aging population and the rising tide of obesity. There are multiple recommendations/guidelines for the management of osteoarthritis. The basis of management should focus on self-management and education, lifestyle modifications, exercise and when appropriate, weight loss. Pharmacotherapy is targeted toward pain palliation with no agents available presently to target prevention and disease modification. The selection of pharmacotherapy should be tailored to the individual, taking into account of personal preferences and interactions with underlying co-morbidities. This editorial provides a guide to the selection process of presently available pharmacotherapy in osteoarthritis.

Association between serum immunoglobulin E levels and knee osteoarthritis in Korean adults

OBJECTIVE

The objective of this study was to examine whether osteoarthritis (OA) in the knees was associated with total immunoglobulin E (IgE), allergen-specific IgE, or allergic sensitizations in a nationally representative population.

METHODS

The study population comprised of 785 adults aged 50 years or more in the Korea National Health and Nutrition Examination Survey 2010. OA was diagnosed as radiographic (rOA) and symptomatic osteoarthritis (sxOA). We performed multivariable logistic regression analyses to investigate relationships of OA in a knee with serum total IgE, allergen (Dermatophagoides farinae, cockroach, and dog allergens)-specific IgE, and allergic sensitizations.

RESULTS

Participants with the highest tertile of the total IgE had 92% and 242% increased risk of knee rOA and sxOA, respectively. Those with D. farinae-specific IgE had 2.2 times increased risk of knee sxOA compared to the lowest tertile. Participants with high total IgE (>150kU/L) had a 60% increased risk of knee rOA. Those with D. farinae-specific sensitization (>0.35kU/L) had 2.0 times increased risk of knee sxOA in compared to those without sensitization. Population-attributable fractions of knee rOA caused by high total IgE and knee sxOA caused by D. farinae-specific sensitization were 9.8% and 15.3%, respectively.

CONCLUSIONS

Total IgE and D. farinae-specific IgE were significantly associated with OA in knees of Korean adults. High total IgE and D. farinae-specific sensitization were also associated with their OA.

Matrix metalloproteinase-13, NF-κB p65 and interleukin-1β are associated with the severity of knee osteoarthritis

Knee osteoarthritis (KOA) is a prevalent disease, especially in the elderly. The present study examined the expression of matrix metalloproteinase-13 (MMP-13), NF-κBp65 and interleukin (IL)-lβ in the synovial tissues of KOA patients and the role of MMP-13 and the NF-κBp65 signalling pathway in KOA pathogenesis. A total of 100 KOA patients were enrolled in our hospital from December 2015 to December 2017 and were classified into either a mild KOA group (Outerbridge grade 1 and 2) or a severe KOA group (Outerbridge grade 3 and 4). Non-OA patients were included as controls. Synovial tissues from patients in both groups were collected for detection of the mRNA and protein expression of MMP-13, NF-κBp65 and IL-lβ. Synovial tissue slices were subjected to haematoxylin and eosin staining and immunohistochemistry (SP method). Cartilage tissues were observed under a light microscope after Safranin O-fast green staining. Reverse transcription-quantitative PCR and western blot analyses demonstrated that the expression of MMP-13, NF-κBp65 and IL-lβ in the mild and severe groups were substantially upregulated compared with the control group (all P<0.05). A positive correlation between MMP-13 and NF-κBp65 expression in the KOA synovial tissues was identified (P<0.05). Immunohistochemistry revealed that the expression of MMP-13 and NF-κBp65 was related to the severity of KOA (MMP-13: severe, 92.54%; moderate, 76.52%; control: 32.14%; and NF-κBp65: severe, 85.56%; moderate, 48.12%; control: 28.32%). This evidence indicated that the severity of KOA was related to MMP-13 and NF-κBp65 expression. The NF-κB signalling pathway may be activated during OA progression, which could upregulate the expression of MMP-13 and IL-1β and accelerate the deterioration of articular cartilage.

Do Nutritional Factors Interact with Chronic Musculoskeletal Pain? A Systematic Review

Dietary patterns may play an important role in musculoskeletal well-being. However, the link between dietary patterns, the components of patients' diet, and chronic musculoskeletal pain remains unclear. Therefore, the purpose of this review was to systematically review the literature on the link between dietary patterns, the components of patients' diet and chronic musculoskeletal pain. This review was conducted following the "Preferred Reporting Items for Systematic reviews and Meta-Analyses" (PRISMA) guidelines and was registered in PROSPERO with the registration number CRD42018110782. PubMed, Web of Science, and Embase online databases were searched. After screening titles and abstracts of 20,316 articles and full texts of 347 articles, 12 eligible articles were included in this review, consisting of nine experimental and three observational studies. Seven out of nine experimental studies reported a pain-relieving effect of dietary changes. Additionally, protein, fat, and sugar intake were found to be associated with pain intensity and pain threshold. In conclusion, plant-based diets might have pain relieving effects on chronic musculoskeletal pain. Patients with chronic rheumatoid arthritis pain can show inadequate intake of calcium, folate, zinc, magnesium, and vitamin B6, whilst patients with fibromyalgia can show a lower intake of carbohydrates, proteins, lipids, vitamin A-E-K, folate, selenium, and zinc. Chronic pain severity also shows a positive relation with fat and sugar intake in osteoarthritis, and pain threshold shows a positive association with protein intake in fibromyalgia.

Osteoarthritis-related nociceptive behaviour following mechanical joint loading correlates with cartilage damage

OBJECTIVE

In osteoarthritis (OA), the pain-structure relationship remains complex and poorly understood. Here, we used the mechanical joint loading (MJL) model of OA to investigate both knee pathology and nociceptive behaviour.

DESIGN

MJL was used to induce OA in the right knees of 12-week-old male C57BL/6 mice (40 cycles, 9N, 3x/week for 2 weeks). Mechanical sensitivity thresholds and weight-bearing ratios were measured before loading and at weeks one, three and six post-loading. At these time points, separate groups of loaded and non-loaded mice (n = 12/group) were sacrificed, joints collected, and fur corticosterone levels measured. μCT analyses of subchondral bone integrity was performed before joint sections were prepared for nerve quantification, cartilage or synovium grading (scoring system from 0 to 6).

RESULTS

Loaded mice showed increased mechanical hypersensitivity paired with altered weight-bearing. Initial ipsilateral cartilage lesions 1-week post-loading (1.8 ± 0.4) had worsened at weeks three (3.0 ± 0.6, CI = -1.8-0.6) and six (2.8 ± 0.4, CI = -1.6-0.4). This increase in lesion severity correlated with mechanical hypersensitivity development (correlation; 0.729, P = 0.0071). Loaded mice displayed increased synovitis (3.6 ± 0.5) compared to non-loaded mice (1.5 ± 0.5, CI = -2.2-0.3) 1-week post-loading which returned to normal by weeks three and six. Similarly, corticosterone levels were only increased at week one post-loading (0.21 ± 0.04 ng/mg) compared to non-loaded controls (0.14 ± 0.01 ng/mg, CI = -1.8-0.1). Subchondral bone integrity and nerve volume remained unchanged.

CONCLUSIONS

Our data indicates that although the loading induces an initial stress reaction and local inflammation, these processes are not directly responsible for the nociceptive phenotype observed. Instead, MJL-induced allodynia is mainly associated with OA-like progression of cartilage lesions.

Neuromuscular exercise and pain neuroscience education compared with pain neuroscience education alone in patients with chronic pain after primary total knee arthroplasty: study protocol for the NEPNEP randomized controlled trial

BACKGROUND

Total knee arthroplasty (TKA) is considered an effective treatment for pain relief and improved physical performances in end-stage knee osteoarthritis. However, several studies have reported less favorable outcomes after TKA with chronic pain rates of approximately 20%. Exercise might be an effective treatment strategy for chronic pain following TKA, but no randomized controlled trials have evaluated its effect. Therefore, the purpose of this randomized controlled trial is to investigate whether a 12-week neuromuscular exercise (NEuroMuscular EXercise training program for patients with knee or hip osteoarthritis assigned for total joint replacement; NEMEX-TJR) program combined with pain neuroscience education (PNE) provides greater pain relief and improvement in physical performances than PNE alone at 12 months follow-up in a population of patients with chronic pain after primary TKA.

METHODS

For this randomized controlled superiority trial, 120 patients with moderate-to-severe chronic pain after TKA are recruited from Aalborg University Hospital, Denmark. Patients are randomly assigned in a 1:1 ratio to one of two interventions: (a) NEMEX-TJR twice weekly for 12 weeks combined with two sessions of PNE or (b) two sessions of PNE given over 6 weeks. Assessment is performed at baseline before intervention and at 3, 6, and 12 months after initiation of the intervention. Outcome assessors are blinded toward group allocation. The primary outcome is the change in the Knee Injury and Osteoarthritis Outcome Score₄ (KOOS₄), defined as the mean score for the KOOS subscales pain, symptoms, activities of daily living, and quality of life. Secondary outcomes include all KOOS subscale scores and scores for PainDETECT, the Fear-Avoidance Beliefs Questionnaire, Global Perceived Effect, the Pain Catastrophizing Scale, pain intensities, temporal summation, conditioned pain modulation, and pressure pain thresholds. Physical performances are measured with walking, stair climbing, and chair standing tests as well as tests of muscle strength and power.

DISCUSSION

The findings will be useful in establishing effective treatment strategies for chronic pain after TKA. The randomized controlled trial involves rigorous scientific methods and uses clinically applicable interventions. The study interventions are conducted in clinical settings, thereby enhancing the possibility of future implementation of the treatments in the health care systems.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03886259. Registered 22 March 2019. Ethics committee registration: N-20180046.

Study on the correlation between knee osteoarthritis and anxiety in patients aged over 55

Introduction. Osteoarthritis, which is a cause of chronic pain and disability with manifestation in any joint, with greater frequency in the joints of the lower limbs, upper limbs, but also at the spine level , affects around 250 million people in the entire world. This condition affects around 10% of the global population (18) and has an impressive impact on people, as it is one of the first 5 causes of disability. Material and method. The objectives of the treatment made by the patients diagnosed with knee osteoarthritis were: pain reduction, increased joint amplitude, increased muscle strength, increased muscle tone, increased quality of life and reintegration into the family and social environment. In the study, there were discussed demographic data regarding the patients. In order to assess the pain parameter, the VAS scale was used, as well as WOMAC subscales. To assess the quality of life of patients with knee osteoarthritis, the QOL scale (Quality of Life) was used. Anxiety was assessed with the help of a test that comprises the evaluation of symptoms at the cognitive, behavioral and physical level. Results and discussions. The pain was evaluated on the VAS scale, having a statistically significant evolution for the evaluation moments. Also with the help of the WOMAC index, two other parameters were evaluated, namely joint rigidity and functional capacity, the results being statistically significant in the 3 evaluation moments. The patients’ anxiety was evaluated with the help of the anxiety test; the results obtained were statistically significant at the 3 evaluation moments. Conclusions. It is vital that the recovery treatment in osteoarthritis be individualized and adapted to the age group. In our group, it enabled the reduction of pain and anxiety, the increase of the functional capacity and the quality of the patients’ lives.Taking into account the fact that the most affected group in the study group was the active professional one, we can evaluate the size of the recovery and the social, family and professional integration for these patients.

Analgesic Effect of Duloxetine on an Animal Model of Monosodium Iodoacetate-Induced Hip Osteoarthritis

We investigated the efficacy of duloxetine on hyperalgesia, histopathological and radiographic findings, pain-related sensory innervation of dorsal-root ganglia (DRG), and spinal changes in a rat model of induced hip osteoarthritis (OA). The right hip joints of male Sprague-Dawley rats (n = 6 rats/group) in the Sham group were injected with 25 μl of sterile saline and 25 μl of sterile saline with 2 mg of monosodium iodoacetate (MIA) were injected to the MIA + Vehicle and MIA + Duloxetine groups. We injected duloxetine 20 mg/kg intraperitoneally in the MIA + Duloxetine group 28 days after injection, whereas rats in the MIA + Vehicle group were injected with 0.5 ml of 20% dimethyl sulfoxide. We assessed hyperalgesia, histopathological changes, immunoreactive (-ir) neurons for calcitonin gene-related peptide and activating transcription factor 3 in DRG, and immunoreactive neurons for ionized-calcium-binding adaptor molecule 1 (Iba1) in the dorsal horn of the spinal cord. MIA administration into the hip joint let to mechanical hyperalgesia of the ipsilateral hind paw (p < 0.05). A single injection of duloxetine significantly attenuated it in induced hip OA (p < 0.05) and suppressed the number of Iba1-ir microglia of the ipsilateral dorsal horn (p < 0.05). These results suggest that a single injection of duloxetine suppressed mechanical hyperalgesia and may influence the expression of Iba1 in the microglia of the ipsilateral dorsal horn in the MIA-induced hip OA. This finding implies the inhibitory effects of duloxetine against neuropathic pain, which may lead to a change of microglial activities. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:422-430, 2020.

Central sensitization in knee osteoarthritis and fibromyalgia: Beyond depression and anxiety

Objectives

To determine the psychopathological profile of patients with central sensitization (CS) in a sample of knee osteoarthritis, with and without CS, and fibromyalgia, and to compare their psychopathological profiles.

Methods

The final sample consists of 19 patients with osteoarthritis and CS (mean 66.37 years ± 8.77), 41 osteoarthritis patients without CS (mean 66.8 ± 7.39 years), 47 fibromyalgia patients (mean 46.47 years ± 7.92) and 26 control subjects (mean 51.56 years ± 11.41). The psychopathological profile was evaluated with the Millon Multiaxial Clinical Inventory.

Results

The average score of MCMI-III reflect higher scores in the fibromyalgia and osteoarthritis-CS groups. Patients with osteoarthritis-CS are more likely to report larger scores in Borderline and Major Depression scales. Fibromyalgia patients are more likely to report more increased scores in Somatoform and Major Depression, versus osteoarthritis-CS group. Fibromyalgia patients versus osteoarthritis without CS are more likely to report higher scores in Schizoid, Depression, Histrionic, Sadistic, Borderline, Somatoform, Posttraumatic Stress Disorder and Major Depression scales.

Discussion

Patients with CS have less differences in their psychopathological profiles as well as in both osteoarthritis groups and greatest differences are obtained between the fibromyalgia and osteoarthritis without CS, so perhaps presence of CS is the key to differentiate those groups and not chronic pain. An exhaustive assessment brings more accurate psychopathological profiles, thus better psychological treatment could be applied.

The Extent of Pain Is Associated With Signs of Central Sensitization in Patients With Hip Osteoarthritis

BACKGROUND

Central sensitization may be present in some patients with hip osteoarthritis (OA), often reflected as widespread pain. We examine the association between pain extent with signs of central sensitization and other clinical and psychological features in patients with hip OA.

METHODS

Thirty patients with hip OA were recruited for this cross-sectional observational study. Participants completed pain drawings on a digital tablet, which displayed frontal and dorsal views of the body. The pain extent (%) for each participant was determined by combining the frontal and dorsal pixels shaded and dividing by the total pixels of the body chart area. Participants completed patient-reported outcome measures to assess for signs and symptoms of central sensitization and psychosocial factors. Quantitative sensory testing including pain pressure thresholds (PPTs) and thermal pressure thresholds was performed at points anatomically local and distant from the hip.

RESULTS

Women had significantly greater pain extent (6.71%) than men (2.65%) (z = -2.76, P < 0.01). Across all participants, increased pain extent was significantly associated with higher scores on the Widespread Pain Index (r₂  = 0.426, P < 0.05), painDETECT questionnaire (r₂  = 0.394, P < 0.05), and Pain Catastrophizing Scale (r₂  = 0.413, P < 0.05), and with lower PPTs at the thenar eminence (r₂  = -0.410, P < 0.05), vastus lateralis (r₂  = -0.530, P < 0.01), vastus medialis (r₂  = 0.363, P < 0.05), and greater trochanter (r₂  = -0.373, P < 0.05).

CONCLUSIONS

Greater pain extent was associated with several measures of signs and symptoms of central sensitization in patients with hip OA. These results support the utility of the pain drawing for identifying signs of central sensitization in patients with hip OA.

Lifestyle and Pain in Women With Knee Osteoarthritis

Osteoarthritis (OA) is the main cause of pain and disability in the elderly. The disease leads to chronic musculoskeletal pain, characterized by an abnormal excitability of pain conduction pathways, and lifestyle may interfere in this pathophysiological aspect. Thus, the aim of this study was to compare perceived pain, pressure pain threshold, and lifestyle of adult and elderly women with and without knee OA. A total of 143 women were recruited and divided into 2 groups: OA (n = 68) and control (n = 75). Volunteers were evaluated for pressure pain tolerance (algometry in vastus medialis and vastus lateralis muscles), perceived pain (visual analogue scale) and lifestyle (FANTASTIC questionnaire). Patients with OA of the present study presented higher weight (P = .001) and body mass index (P < .001) than controls. Results also revealed less tolerance to pressure pain (P < .001) and higher pain perception (P < .001) in patients with OA. OA group scored significantly lower in lifestyle questionnaire than controls (P = .03). Patients with OA in the present study who presented lifestyle scores below median presented significantly higher values of pain perception than the ones above it (P = .03). In conclusion, patients with OA present more sensitivity to pain, more perceived pain, and worse lifestyle than healthy individuals.

Association of preoperative pain in knee and external to knee with postoperative pain outcome after total knee arthroplasty

Background

Preoperative pain in the symptomatic knee may predict postoperative pain severity in patients undergoing total knee arthroplasty (TKA). However, the effect of preoperative pain external to the knee on postoperative pain is unclear. This study evaluated postoperative pain outcomes in TKA patients according to the presence of preoperative pain in the knee only or in the knee and external to the knee.

Methods

We retrospectively assessed medical records of patients who underwent unilateral TKA. The relationship between reported preoperative pain characteristics and morphine equivalent consumption or numerical rating scale (NRS) pain scores on postoperative day (POD) 0-3 was assessed using a multivariable generalized linear model.

Results

In total, 3,429 adult patients who underwent their first TKA were included; 2,864 (83.5%) patients preoperatively experienced only knee pain and 565 (16.5%) knee pain with external to knee pain. Preoperative pain in the knee and external to the knee was associated with 5% higher morphine equivalent consumption on POD 0-3 compared to preoperative knee pain only (exponentiated regression coefficient: 1.05; 95% confidence interval: 1.02 to 1.09; P = 0.004). However, the NRS pain scores on POD 0, 1, 2, and 3 and adjuvant analgesics consumption (acetaminophen and ketorolac) on POD 0-3 were not significantly different between the two groups (P > 0.05).

Conclusions

This study showed that there was an increase of morphine equivalent consumption during POD 0-3 in patients with preoperative knee pain with external to knee pain than in patients with preoperative only knee pain.

Best Evidence Rehabilitation for Chronic Pain Part 5: Osteoarthritis

Osteoarthritis (OA) is a leading cause of chronic pain and disability in older adults, which most commonly affects the joints of the knee, hip, and hand. To date, there are no established disease modifying interventions that can halt or reverse OA progression. Therefore, treatment is focused on alleviating pain and maintaining or improving physical and psychological function. Rehabilitation is widely recommended as first-line treatment for OA as, in many cases, it is safer and more effective than the best-established pharmacological interventions. In this article, we describe the presentation of OA pain and give an overview of its peripheral and central mechanisms. We then provide a state-of-the-art review of rehabilitation for OA pain—including self-management programs, exercise, weight loss, cognitive behavioral therapy, adjunct therapies, and the use of aids and devices. Next, we explore several promising directions for clinical practice, including novel education strategies to target unhelpful illness and treatment beliefs, methods to enhance the efficacy of exercise interventions, and innovative, brain-directed treatments. Finally, we discuss potential future research in areas, such as treatment adherence and personalized rehabilitation for OA pain.

Cannabinoids in the treatment of rheumatic diseases: Pros and cons

Medical cannabis is being increasingly used in the treatment of rheumatic diseases because, despite the paucity of evidence regarding its safety and efficacy, a growing number of countries are legalising its use for medical purposes in response to social pressure. Cannabinoids may be useful in the management of rheumatic disorders for two broad reasons: their anti-inflammatory and immunomodulatory activity, and their effects on pain and associated symptoms. It is interesting to note that, although a wide range of medications are available for the treatment of inflammation, including an ever-lengthening list of biological medications, the same is not true of the treatment of chronic pain, a cardinal symptom of many rheumatological disorders. The publication of systematic reviews (SR) concerning the use of cannabis-based medicines for chronic pain (with and without meta-analyses) is outpacing that of randomised controlled trials. Furthermore, narrative reviews of public institution are largely based on these SRs, which often reach different conclusions regarding the efficacy and safety of cannabis-based medicines because of the lack of high-quality evidence of efficacy and the presence of indications that they may be harmful for patients. Societal safety concerns about medical cannabis (e.g. driving risks, workplace safety and pediatric intoxication) must always be borne in mind, and will probably not be addressed by clinical studies. Medical cannabis and cannabis-based medicines have often been legalised as therapeutic products by legislative bodies without going through the usual process of regulatory approval founded on the results of traditional evidence-based studies. This review discusses the advantages and limitations of using cannabis to treat rheumatic conditions.

Association of osteoarthritis and pain with Alzheimer's Diseases and Related Dementias among older adults in the United States

BACKGROUND

Emerging evidence suggests that Pain Interference (PI) and certain chronic pain conditions, including Osteoarthritis (OA) may be associated with risk for Alzheimer's disease and Related Dementias (ADRD). However, research exploring the relation of OA and PI to ADRD remains sparse.

OBJECTIVE

To assess the association of OA and PI to ADRD using cross-sectional data from a representative sample of USA adults aged ≥65 years.

DESIGN

Retrospective cross-sectional.

STUDY SAMPLE

Older adults (age ≥ 65 years) drawn from the Medical Expenditure Panel Survey (MEPS, 2009-2015).

METHODS

OA was identified using both medical conditions files and participant responses to arthritis-specific queries. ADRD was ascertained using the medical conditions files. PI was defined as reported frequent PI with normal activities (PIA). OA and PIA were categorized as a composite variable: 1) OA with PIA; 2) OA without PIA; 3) No OA with PIA; and 4) No OA and no PIA (reference group). Adjusted associations of OA and PIA to ADRD were assessed using logistic regression and adjusted for biological, demographic, socio-economic, lifestyle, and health conditions.

RESULTS

Overall, 27.1% had OA, of whom 47.6 % reported PIA vs 31.1% of those without OA; 2.8% had diagnosed ADRD. Adults with PIA either with or without OA had significantly higher odds of ADRD relative to those without OA or PIA (Adjusted odd ratios (AOR's) = 1.37, 95%CI - 1.01, 1.86 (p = 0.04) and 1.44, 95%CI - 1.13, 1.82 (p = 0.003), respectively).

CONCLUSION

PIA in both the presence and absence of OA remained significantly and positively associated with ADRD after adjustment for multiple confounders.

Application of ICD-11 among individuals with chronic pain: A post hoc analysis of the Stanford Self-Management Program

BACKGROUND

Chronic primary pain (CPP) is one of seven diagnostic groups within the proposed classification of chronic pain in ICD-11. Our aims were to apply the proposed ICD-11 criteria in a large cohort of chronic pain patients participating in the Chronic Pain Self-Management Program (CPSMP) and further investigate whether participants with CPP differed from participants with chronic secondary pain (CSP) regarding health, health expenditure and the effect of participating in the CPSMP.

METHODS

A secondary analysis of a randomized, controlled trial on the effect of the CPSMP. Four examiners categorized participants' pain according to ICD-11 using register-based medical diagnoses and patients' self-reported symptoms. Afterwards, differences between CPP and CSP were examined.

RESULTS

Out of 394 participants, 312 were successfully classified into CPP (n = 164) or CSP (n = 148) whereas 76 had a mixed pain condition. Participants with CPP were younger, more likely to be women, and had longer pain duration compared to participants with CSP. Participants with CPP reported worse health-related quality of life on the SF-36 Mental Component Summary and subscales of vitality, social functioning and bodily pain. Participants with CSP had more physical comorbidities and higher total health expenditure. None of the groups benefitted from the CPSMP.

CONCLUSIONS

We successfully applied the new classification of chronic pain in ICD-11 on the basis of ICD-10 medical diagnoses and symptom self-report. Participants with CPP differed significantly from participants with CSP on baseline characteristics, self-reported health measures and total health expenditure. The CPSMP was not effective in any of the groups.

SIGNIFICANCE

The current study applies the proposed new classification of chronic pain in ICD-11 and shares the experiences of the diagnostic rating procedure of individuals with chronic pain. Furthermore, it evaluates the effect of the Stanford Self-Management Program.

Transcutaneous Electrical Nerve Stimulation Reduces Knee Osteoarthritic Pain by Inhibiting Spinal Glial Cells in Rats

BACKGROUND

Transcutaneous electrical nerve stimulation (TENS) is commonly used for pain control. However, the effects of TENS on osteoarthritis (OA) pain and potential underlying mechanisms remain unclear.

OBJECTIVE

The objective of this study was to investigate the effect of TENS on OA pain treatment and underlying mechanisms related to glial cell inhibition.

DESIGN

This was an experimental study.

METHODS

OA was induced by injection of monosodium iodoacetate into the synovial space of the right knee joint of rats. High-frequency (HF) TENS (100 Hz), low-frequency (LF) TENS (4 Hz), or sham TENS was applied to the ipsilateral knee joint for 20 minutes. Paw withdrawal threshold (PWT), weight bearing, and knee bend score (KBS) were measured. Immunohistochemistry for microglia and astrocytes was performed with L3 to L5 spinal segment samples. To investigate the effects of glial inhibition on OA pain, minocycline, l-α-aminoadipate, or artificial cerebrospinal fluid was injected intrathecally, and PWT and KBS were measured.

RESULTS

Compared with sham TENS, both HF TENS and LF TENS significantly increased PWT, decreased KBS, and inhibited activated microglia in the L3 to L5 segments but did not decrease the total number of microglia, except in the L4 segment (HF TENS). Astrocyte expression was significantly decreased in the L3 to L5 segments following LF TENS and in the L3 segment following HF TENS. Compared with artificial cerebrospinal fluid, both minocycline and l-α-aminoadipate increased PWT and decreased KBS.

LIMITATIONS

These results cannot be generalized to humans.

CONCLUSIONS

TENS alleviates OA pain in rats by inhibiting activated microglia and reducing astrocyte expression in the spinal cord. Although these results may not be generalizable to chronic pain in patients with OA, within the limitation of the experimental animal model used in the present study, they suggest a possible mechanism and preclinical evidence supporting further experimentation or clinical use of TENS in humans.