Cold Pain Threshold Identifies a Subgroup of Individuals With Knee Osteoarthritis That Present With Multimodality Hyperalgesia and Elevated Pain Levels

Activity-related pain and sensitization predict within- and between-person pain experience in people with knee osteoarthritis: An ecological momentary assessment study

Background and objectives

Knee Osteoarthritis (OA) is a prevalent musculoskeletal condition that often results in pain and disability. Determining factors predicting variability in pain experience is critical to improving clinical outcomes. Underlying pain sensitization and its clinical manifestations, such as activity-related pain, may better predict the knee OA pain experience. This study aimed to determine whether Quantitative Sensory Testing (QST) derived sensitization measures and activity-related pain predict knee OA pain experiences collected via smartphone ecological momentary assessment (EMA).

Design

Individuals with knee OA were recruited from an urban community in New Zealand. Those eligible to participate underwent baseline QST with clinical measures of activity-related pain also being collected. The knee OA pain experience was collected via smartphone EMA three times daily for two weeks. Mixed effects location scale models were developed using a multilevel modelling approach.

Results

Eighty-six participants with knee OA participated in the study. Mean age was 67.3 years, with most of the participants being female (64%) and New Zealand European (90.6%). Activity-related pain predicted worse and more variable pain intensity, pain interference, and bothersomeness outcomes within and between individuals with knee OA. Widespread cold hyperalgesia and local mechanical hyperalgesia were shown to predict higher within-person variability in pain intensity and pain interference respectively, while mechanical temporal summation predicted less within-person variability in pain intensity and interference.

Discussion

Those demonstrating activity-related pain and sensitization could be at risk of experiencing worse and more variable knee OA pain in the subsequent weeks. Testing for sensitization in clinical practice could therefore identify those at greatest risk of higher and more variable knee OA pain experiences and in greatest need of treatment. Larger validation studies are required, which include individuals with more severe knee OA.

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.

The application of human medical image-based finite element analysis in the construction of mouse osteoarthritis models

The anterior cruciate ligament plays an important role in maintaining the stability of the knee joint. Its injury is a common cause of articular cartilage degeneration and osteoarthritis (OA). The anterior cruciate ligament transection (ACLT) method is commonly employed to construct animal models for studying osteoarthritis pathogenesis. However, the precise mechanism of how anterior cruciate ligament injury leads to osteoarthritis is not fully understood. This study utilized finite element analysis (FEA) with human medical images to simulate the biomechanical characteristics of anterior cruciate ligament (ACL) injury. Osteoarthritis models were subsequently established in C57BL/6 mice using ACLT to explore the link between ACL injury and osteoarthritis development. The results of FEA showed that, after an anterior cruciate ligament injury, abnormal stress was concentrated in the medial and lateral of the femoral and tibial articular cartilage during knee flexion and extension. In order to better display the pathological changes of articular cartilage in the stress areas, the medial tibial cartilage was selected as a representative area to observe the continuous pathological changes of articular cartilage in ACLT-induced OA mice. The articular cartilage degeneration was most dramatic at four weeks post ACLT operation and then remained relatively stable. This study may have significant implications for the development of animal models of osteoarthritis and provide a reference for histopathological research on osteoarthritis.

High intensity interval training attenuates osteoarthritis-associated hyperalgesia in rats

High-intensity interval training (HIIT) is a physical therapy that may benefit patients with osteoarthritis (OA). Cacna2d1 is a calcium channel subunit protein that plays an important role in the activity of nerve cells. However, there is currently no evidence on HIIT relieving OA-associate hyperalgesia by decreased Cacna2d1. Our study established the OA rat models with intra-articular injection of monosodium iodoacetate (MIA). This experiment was divided into two stages. The first stage comprised three groups: the control, OA, and OA-HIIT groups. The second stage comprised two groups, including the AAV-C and AAV-shRNA-Cacna2d1 groups. OA rats were positioned at the L5-L6 segments, and 20 µl of AAV virus was injected intrathecally. The pain threshold, cartilage analysis, Cacna2d1, and pain neurotransmitters were measured and compared. The pain threshold was significantly lower in OA rats than in control rats from the first to the tenth week. Starting from the sixth week, OA-HIIT rats exhibited significantly increased pain thresholds. The expression of Cacna2d1 increased in OA rats. Moreover, the knockdown of Cacna2d1 significantly down-regulated the expression of c-Fos, SP, and Vglut2 in the posterior horn of the spinal cord. In conclusion, HIIT attenuates OA-associated hyperalgesia, which may be related to the down-regulation of Cacna2d1.

High Prevalence of Pain Sensitization in Knee Osteoarthritis: A Meta-Analysis with Meta-Regression

OBJECTIVE

The aim of this meta-analysis was to study the evidence on pain sensitization in knee osteoarthritis (OA), providing a quantitative synthesis of its prevalence and impact. Factors associated with pain sensitization were also investigated.

METHODS

Meta-analysis; PubMed (MEDLINE), Cochrane Central Register (CENTRAL), and Web of Science were searched on February 2021. Level I to level IV studies evaluating the presence of pain sensitization in patients with symptomatic knee OA, documented through a validated method (questionnaires or quantitative sensory testing), were included. The primary outcome was the prevalence of pain sensitization. Factors influencing the prevalence were also evaluated, as well as differences in terms of pain thresholds between knee OA patients and healthy controls.

RESULTS

Fifty-three articles including 7,117 patients were included. The meta-analysis of proportion documented a prevalence of pain sensitization of 20% (95% confidence interval [CI] = 16%-26%) with a significant heterogeneity of results (I² = 89%, P < 0.001). The diagnostic tool used was the main factor influencing the documented prevalence of pain sensitization (P = 0.01). Knee OA patients presented higher pain sensitivity compared with healthy controls, both in terms of local pressure pain threshold (standardized mean difference [SMD] = -1.00, 95% CI = -1.67 to -0.32, P = 0.007) and distant pressure pain threshold (SMD = -0.54, 95% CI = -0.76 to -0.31, P < 0.001).

CONCLUSIONS

Knee OA pain presents features that are consistent with a significant degree of pain sensitization. There is a high heterogeneity in the reported results, mainly based on the diagnostic tool used. The identification of the best methods to detect pain sensitization is warranted to correctly evaluate and manage symptoms of patients affected by knee OA.

REGISTRATION

PROSPERO CRD42019123347.

Overview of Registered Clinical Trials on Manual Therapy: Possible Implications of Genetic Testing for Personalized Treatment

BACKGROUND/AIM

Manual therapy (MT) is a frequently applied intervention offering individualized treatment in the clinic. In addition to the traditional approaches of MT, measuring molecular response to MT may offer better understanding of MT outcomes in order to provide specific personalized treatment. The aim of this study was to summarize MT-related registered clinical trials, as well as to search for any evidence on MT and genetics.

PATIENTS AND METHODS

A comprehensive search was conducted within the Clinical Trials database with predefined keywords mining for all types of MT-related clinical trials.

RESULTS

From the 47 trials, 20 had results and 27 had no results. MT alleviated pain and improved function almost in all trials. One registered clinical trial had investigated molecular outcomes of MT.

CONCLUSION

MT is an effective and individualized treatment offering option in the management of several conditions. Interestingly, a clinical trial was found investigating molecular genetics and MT pinpointing an already existing link between genetics and MT. Therefore, further clinical trials may focus on genetics and MT for providing specific personalized treatment in future.

Quantitative sensory testing: identifying pain characteristics in patients with osteoarthritis

OBJECTIVE

This review outlines the most commonly used quantitative sensory tests to identify pain sensitization. We examine cross-sectional associations between quantitative sensory testing (QST) measures and OA symptoms and severity, along with longitudinal associations between QST findings and response to surgical and non-surgical treatments for OA.

DESIGN

We conducted a search in PubMed for English language papers including 'osteoarthritis' and 'quantitative sensory testing' as search terms. Papers that did not pertain specifically to OA or QST were excluded.

RESULTS

Pressure Pain Threshold (PPT), Conditioned Pain Modulation (CPM), and Temporal Summation (TS) are the QST measures used most frequently to identify pain sensitization. Findings indicate that persons with knee OA often exhibit lower PPT thresholds, inefficient CPM, and facilitated TS as compared with controls who do not have OA, supporting the discriminant validity of QST. Pre-treatment QST has shown some success in identifying persons who experience less pain relief from surgical and non-surgical treatments for knee OA. Post-treatment QST has shown that sometimes PPT and CPM can normalize (PPT thresholds increase, and CPM becomes efficient) in patients for whom joint replacement is successful. Recent studies indicate that QST measures are more closely associated with pain severity than OA radiographic severity, suggesting that sensitization may be a trait rather than a state.

CONCLUSIONS

QST may have a role in identifying persons who are susceptible to chronic pain and may offer an opportunity for personalized, more effective treatment of OA.

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

OBJECTIVE

This scoping review analyzed various quantitative sensory testing methodologies used in the assessment of sensitization and how sensitization is defined in people with knee osteoarthritis.

DESIGN

A scoping review.

SETTING

All clinical and research settings.

SUBJECTS

Non-surgical adults with knee osteoarthritis.

METHODS

This scoping review was guided by existing scoping review methodologies. Relevant studies were extracted from the following electronic databases: Medical Literature Analysis and Retrieval System Online, Excerpta Medica Database, Allied and Complementary Medicine Database and the Cumulative Index to Nursing Allied Health Literature. Abstract and full article screening and data extraction were performed in pairs. Information on quantitative sensory testing techniques and parameters was extracted and summarized in tables. General and technique specific definitions of sensitization were extracted from included texts.

RESULTS

Our search yielded 4199 articles, of which 50 were included in our review. The most common quantitative sensory test was pressure pain threshold. In total 28 unique testing sites were found speaking to the high degree of variability between studies. Sensitization was poorly defined with only 8 studies fully operationalizing it, 22 partially, and the remainder did not provide sufficient information to meet our criteria.

CONCLUSION

This scoping review has provided an overview of the most common methods of quantitative sensory testing being implemented in the assessment of nervous system sensitization to nociceptive signaling in people with knee osteoarthritis. This study provides a foundation for future development of quantitative sensory testing methodology for research and clinical practice in the osteoarthritis population.

Exploring the Pain in Patellofemoral Pain: A Systematic Review and Meta-Analysis Examining Signs of Central Sensitization

BACKGROUND

Patellofemoral pain (PFP) has high recurrence rates and minimal long-term treatment success. Central sensitization refers to dysfunctional pain modulation that occurs when nociceptive neurons become hyperresponsive. Researchers in this area of PFP have been increasingly productive in the past decade.

OBJECTIVE

To determine whether evidence supports manifestations of central sensitization in individuals with PFP.

DATA SOURCES

We searched MeSH terms for quantitative sensory testing (QST) pressure pain thresholds (PPTs), conditioned pain modulation (CPM), temporal summation, sensitization, hyperalgesia, and anterior knee pain or PFP in PubMed, SPORTDiscus, CINAHL, Academic Search Complete, and EBSCOhost.

STUDY SELECTION

Peer-reviewed studies that were written in English and published between 2005 and 2020 and investigated QST or pain mapping in a sample with PFP were included in this review.

DATA EXTRACTION

The initial search yielded 140 articles. After duplicates were removed, 78 abstracts were reviewed. The full text of 21 studies was examined, and we included 15 studies in our evaluation: 6 in the meta-analysis, 4 in the systematic review, and 5 in both the meta-analysis and systematic review.

DATA SYNTHESIS

A random-effects meta-analysis was conducted for 4 QST variables (local PPTs, remote PPTs, CPM, temporal summation). Strong evidence supported lower local and remote PPTs, impaired CPM, and facilitated temporal summation in individuals with PFP compared with pain-free individuals. Evidence for heat and cold pain thresholds was conflicting. Pain mapping demonstrated expanding pain patterns associated with long duration of PFP symptoms.

CONCLUSIONS

Signs of central sensitization were present in individuals with PFP, indicating altered pain modulation. The etiologic and treatment models of PFP should reflect the current body of evidence regarding central sensitization. Signs of central sensitization should be monitored clinically, and treatments with central effects should be considered as part of a multimodal plan of care.

Contribution of COMT and BDNF Genotype and Expression to the Risk of Transition From Acute to Chronic Low Back Pain

OBJECTIVES

A number of factors, including heritability and the environment, contribute to risk of transition from acute low back pain to chronic low back pain (CLBP). The aim of this study was to (1) compare somatosensory function and pain ratings at low back pain (LBP) onset between the acute low back pain and CLBP conditions and (2) evaluate associations between BDNF and COMT polymorphisms and expression levels at LBP onset to acute and chronic pain burden and risk for transition to the chronic pain state.

METHODS

In this longitudinal study, 220 participants were enrolled following recent onset of LBP and data were collected until the LBP resolved or until the end of the study at 6 months. Forty-two participants' pain resolved before 6 weeks from onset and 42 participants continued to have pain at 6 months. Patient-reported pain burden, somatosensory function (quantitative sensory testing), and blood samples were collected at each study visit.

RESULTS

CLBP is associated with greater pain burden and somatosensory hypersensitivity at the time of LBP onset. COMT rs4680 genotype (GG) was associated with acute cold pain sensitivity and with the risk for transition to CLBP while COMT expression was independently associated with risk for transition.

DISCUSSION

CLBP was characterized by higher reported pain burden and augmented hypersensitivity at LBP onset. COMT expression and genotype were associated with acute pain burden and likelihood of transition to CLBP.

[Pain evolution in patients with central sensitization and osteoarthritis after knee arthroplasty]

INTRODUCTION

In patients with knee osteoarthritis, a group of 30% has been identified with central pain sensitization (CPS). The aim is to analyze the persistence of CPS in patients after knee arthroplasty and its correlation with pain intensity, functionality, determining factors and to evaluate physical examination as an assessment instrument.

MATERIAL AND METHODS

Quasi-experimental before-after study of patients operated on total knee arthroplasty. The evolution of subjective variables (pain characteristics, painDETECT questionnaire, WOMAC and Numerical Rating Scale) and physical examination (thermal hyperalgesia, allodynia, hypoesthesia, algometry and goniometry) 3 months before and 3 and 6 months after surgery are analysed using repeated measures ANOVA test for the quantitative ones and Cochran's Q for the qualitative ones. Spearmen test was used for the correlation of the questionnaires, the PD-Q and exploration variables and for the multivariate model of the PD-Q with clinical determinants.

RESULTS

Sixty-seven patients completed the study. The evolution of the quantitative and qualitative variables was significant, with a correlation between questionnaires. In the linear multivariate model of PD-Q, a significant relationship was obtained from personal history of flexion limitation, chronic musculoskeletal pain and the association between depression and time.

CONCLUSIONS

A significant percentage of patients with knee osteoarthritis after arthroplasty persisted with probable CPS, correlating with intensity and functionality. The limitation of mobility and previous chronic comorbidity could be determinants of CPS, with anamnesis and exploration being useful tools in consultation.

Prospective correlational time-series analysis of the influence of weather and air pollution on joint pain in chronic rheumatic diseases

OBJECTIVES

The primary objective was to evaluate the association between weather variables and joint pain in patients with chronic rheumatic diseases (CRD: rheumatoid arthritis (RA), osteoarthritis (OA), and spondyloarthritis (SpA)). A secondary objective was to study the impact of air pollution indicators on CRD pain.

METHOD

The study is prospective, correlational, with time-series analysis. Patients with CRD, living in a predefined catchment area, filled their level of pain daily using a 0-10 numerical scale (NS), for 1 year. Weather (temperature, relative humidity (H), atmospheric pressure (P)) and air pollution indicators (particulate matters (PM₁₀, PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃)) were recorded daily using monitoring systems positioned in the same area. Association between pain and weather and air pollution indicators was studied using Pearson's correlation. Time-series analysis methodology was applied to determine the temporal relationship between pain and indicators.

RESULTS

The study included 94 patients, 82% reported they were weather-sensitive. Pain variation was similar across diseases over a year. Pain was associated negatively with temperature, H, and O_3, and positively with P and NO₂. However, the strength of correlation was moderate; temperature explained 22% of pain variance. A drop of 10°C in temperature corresponded to an increase of 0.5 points in pain NS. Also, there was a significant interaction among environmental factors. In time-series analysis, temperature and NO₂ remained independently associated with pain.

CONCLUSIONS

The perception of joint pain in patients with CRD was correlated with weather and air pollution. The strength of association was moderate and independent of underlying disease. Key Points •Weather variation was moderately correlated with joint pain in chronic rheumatic diseases, with an inverse association with temperature, humidity, and O₃. • Air pollution indicators, mainly nitrogen dioxide and ozone, were correlated with joint pain; particulate matters were also correlated but to a lesser extent. • The influence of these environmental factors was independent of the type of rheumatic disease, thus raising the hypothesis of their impact on pain perception mechanisms.

Pain-related behavior is associated with increased joint innervation, ipsilateral dorsal horn gliosis, and dorsal root ganglia activating transcription factor 3 expression in a rat ankle joint model of osteoarthritis

Supplemental Digital Content is Available in the Text.

In a rat model of osteoarthritis, we found increased joint sensory and sympathetic innervation and glia changes in dorsal horn, accompanying pain-related behavior onset.

Introduction:

Osteoarthritis (OA)-associated pain is often poorly managed, as our understanding of the underlying pain mechanisms remains limited. The known variability from patient to patient in pain control could be a consequence of a neuropathic component in OA.

Methods:

We used a rat monoiodoacetate model of the ankle joint to study the time-course of the development of pain-related behavior and pathological changes in the joint, dorsal root ganglia (DRG), and spinal cord, and to investigate drug treatments effects.

Results:

Mechanical hypersensitivity and loss of mobility (as assessed by treadmill) were detected from 4 weeks after monoiodoacetate. Cold allodynia was detected from 5 weeks. Using histology and x-ray microtomography, we confirmed significant cartilage and bone degeneration at 5 and 10 weeks. We detected increased nociceptive peptidergic and sympathetic fiber innervation in the subchondral bone and synovium at 5 and 10 weeks. Sympathetic blockade at 5 weeks reduced pain-related behavior. At 5 weeks, we observed, ipsilaterally only, DRG neurons expressing anti-activating transcription factor 3, a neuronal stress marker. In the spinal cord, there was microgliosis at 5 and 10 weeks, and astrocytosis at 10 weeks only. Inhibition of glia at 5 weeks with minocycline and fluorocitrate alleviated mechanical allodynia.

Conclusion:

Besides a detailed time-course of pathology in this OA model, we show evidence of contributions of the sympathetic nervous system and dorsal horn glia to pain mechanisms. In addition, late activating transcription factor 3 expression in the DRG that coincides with these changes provides evidence in support of a neuropathic component in OA pain.

Cryotherapy Improves Limb Use But Delays Normothermia Early After Stifle Joint Surgery in Dogs

Objective: To evaluate the short-term efficacy and safety of cold compression therapy (CCT) relative to a soft padded bandage (SPB) in dogs undergoing surgery to manage cranial cruciate ligament injury. Methods:Dogs were randomized into groups that received CCT or SPB after surgery. Weight bearing was measured using a weight distribution platform before and the day after surgery. Stifle joint flexion and extension were measured using a goniometer before and the day after surgery. Rectal temperatures were measured every 15 min for 2 h after surgery and the morning after surgery. Mechanical nociceptive thresholds (MNT) were measured using an algometer the day after surgery. Findings in both groups were compared using a mixed model ANOVA. Results:20 dogs were enrolled: 10 in the CCT and 10 in the SPB group. Dogs undergoing CCT had more stifle joint flexion (P = 0.008) and weight bearing (P < 0.001) after surgery than dogs with SPB. MNT after surgery correlated statistically with stifle joint flexion after surgery (r = -0.315, P = 0.014), extension after surgery (r = 0.310, P = 0.016), and weight bearing after surgery (r = 0.314, P = 0.003). Return to normothermia was delayed in the CCT group, with temperatures ~0.5°C (1.0°F) lower 105 (P = 0.018) and 120 min (P = 0.013) after surgery. Conclusion:Relative to bandaging, CCT had a positive short-term impact on stifle flexion and weight bearing. CCT delayed warming after surgery but dogs were only mildly hypothermic [0.5°C [1.0°F]].

Association of weather factors with the risk of pain exacerbations in people with hip osteoarthritis

Objectives: Our objective was to evaluate the association of weather factors with the risk of pain exacerbations in people with symptomatic hip osteoarthritis (OA). Method: Eligible participants with symptomatic hip OA were instructed to log on to the study website and complete questionnaires every 10 days and additionally whenever they considered they were experiencing a pain exacerbation (case period) during the 90 day follow-up. Pain exacerbation was defined as an increase of two points in pain intensity on an 11-point numeric rating scale (0-10) during the follow-up compared with baseline. Each case period was anchored to four control periods within a 35 day interval using a time-stratified approach. Weather data were obtained for both periods from the publicly available meteorological database of the Australian Bureau of Meteorology. We examined the association of weather factors across 72 h before the index date with the risk of pain exacerbation, using conditional logistic regression. Results: Among 252 participants recruited, 129 participants had at least one episode of pain exacerbation and were included in the analysis. A significant dose-response relationship was found between average daily temperature variation in the prior 72 h and risk of pain exacerbations (p = 0.04 for linear trend). There was no significant association between maximum daily temperature, minimum daily temperature, relative humidity, precipitation, or barometric pressure and hip pain exacerbations. Conclusion: The overall results suggest that only daily temperature variation among different weather factors was associated with hip pain exacerbations in people with symptomatic hip OA.

Pain and Problem Behavior in Cats and Dogs

We argue that there is currently an under-reporting of the ways in which pain can be associated with problem behavior, which is seriously limiting the recognition of this welfare problem. A review of the caseloads of 100 recent dog cases of several authors indicates that a conservative estimate of around a third of referred cases involve some form of painful condition, and in some instances, the figure may be nearly 80%. The relationship is often complex but always logical. Musculoskeletal but also painful gastro-intestinal and dermatological conditions are commonly recognized as significant to the animal's problem behavior. The potential importance of clinical abnormalities such as an unusual gait or unexplained behavioral signs should not be dismissed by clinicians in general practice, even when they are common within a given breed. In general, it is argued that clinicians should err on the side of caution when there is a suspicion that a patient could be in pain by carefully evaluating the patient's response to trial analgesia, even if a specific physical lesion has not been identified.

Global management of patients with knee osteoarthritis begins with quality of life assessment: a systematic review

Background

Knee osteoarthritis (KOA) is a prevalent form of chronic joint disease associated with functional restrictions and pain. Activity limitations negatively impact social connectedness and psychological well-being, reducing the quality of life (QoL) of patients. The purpose of this review is to summarize the existing information on QoL in KOA patients and share the reported individual factors, which may influence it.

Methods

We conducted a systematic review examining the literature up to JAN/2017 available at MEDLINE, EMBASE, Cochrane, and PsycINFO using KOA and QOL related keywords. Inclusion criteria were QOL compared to at least one demographic factor (e.g., age, gender), lifestyle factor (e.g., functional independence), or comorbidity factor (e.g., diabetes, obesity) and a control group. Analytical methods were not considered as part of the original design.

Results

A total of 610 articles were reviewed, of which 62 met inclusion criteria. Instruments used to measure QoL included: SF-36, EQ-5D, KOOS, WHOQOL, HAS, AIMS, NHP and JKOM. All studies reported worse QoL in KOA patients when compared to a control group. When females were compared to males, females reported worse QOL. Obesity as well as lower level of physical activity were reported with lower QoL scores. Knee self-management programs delivered by healthcare professionals improved QoL in patients with KOA. Educational level and higher total mindfulness were reported to improve QoL whereas poverty, psychological distress, depression and lacking familial relationships reduce it. Surgical KOA interventions resulted in good to excellent outcomes generally; although, results varied by age, weight, and depression.

Conclusion

KOA has a substantial impact on QoL. In KOA patients, QoL is also influenced by specific individual factors including gender, body weight, physical activity, mental health, and education. Importantly, education and management programs designed to support KOA patients report improved QoL. QoL data is a valuable tool providing health care professionals with a better comprehension of KOA disease to aid implementation of the most effective management plan.

A population-based examination of suicidality in comorbid generalized anxiety disorder and chronic pain

BACKGROUND

Generalized anxiety disorder (GAD) and chronic pain conditions commonly co-occur, and are both independently associated with suicidality; however, little is known about the impact of chronic pain on suicidality among individuals with GAD. The aim of this study was to examine the associations between comorbid GAD and chronic pain conditions with suicide ideation, plans, and attempts in a population-based sample.

METHODS

We analyzed data from the 2012 Canadian Community Health Survey-Mental Health (CCHS-MH; N = 25,113). Multiple logistic regressions examined the associations between comorbid GAD and chronic pain conditions (i.e., arthritis, migraine, back pain; reference = GAD alone) with suicidality (i.e., ideation, plans, and attempts).

RESULTS

After adjusting for sociodemographics, other psychiatric conditions, and other chronic pain conditions, results indicated that compared to GAD alone, comorbid GAD and migraine was associated with increased odds of suicide ideation and plans (adjusted odds ratio (AOR) range: 2.55-3.00) and comorbid GAD and arthritis was associated with increased odds of suicide attempts (AOR = 4.10, 95% CI [1.05-16.01]).

LIMITATIONS

The cross-sectional nature of the survey design does not permit causal assumptions regarding the emergent associations and the self-report assessment of chronic pain conditions may be associated with response biases.

CONCLUSIONS

Results highlight the burden of chronic pain on suicidality among individuals with GAD. These results emphasize the importance of assessing risk of suicidality among individuals with comorbid GAD and chronic pain conditions, particularly migraine and arthritis.

Development of a topical menthol stimulus to evaluate cold hyperalgesia

PURPOSE

Cold hyperalgesia is an indicator of widespread pain sensitivity and is associated with poor clinical outcomes. Menthol activates TRPM8, a cold-sensing receptor channel. This research evaluated topical menthol as a potential stimulus to be used in the clinical evaluation of cold hyperalgesia.

METHODS

Participants were 59 pain free volunteers (17 male: 42 female). A blinded, repeated measures design was used. Participants received applications of menthol at different concentrations in a liquid (study 1) or gel (study 2) formulation with a 24-h interval between each application. Each menthol concentration was applied for 15 min and participants were asked to rate the sensation produced using a series of visual analogue scales and by selecting words from a descriptor list derived from the McGill pain questionnaire (MPQ). The menthol was applied to a site on the volar forearm. Participants also had their cold pain thresholds (CPT) evaluated at the same site using a contact thermode.

RESULTS

There were significant concentration-dependent effects for intensity of cold, unpleasantness and pain VAS: cold F_(2,62) = 8.67, p < 0.001; unpleasantness χ²(₂) = 14.14, p < 0.001; χ²(₂) = 11.74, p = 0.003, with moderate effect sizes for unpleasantness and pain. There were also significant concentration dependent effects for descriptor indices, pain rating index (PRI) F_(2,62) = 26.33, p < 0.001; number of words chosen (NWC) F_(2,62) = 19.62, p < 0.001, with large effect sizes for 10-20% and 10-30% comparisons. Significant correlations were seen between measures of unpleasantness, pain, PRI, NWC and CPT dependent on menthol concentration.

CONCLUSION

Topical menthol has potential as a stimulus to evaluate cold hyperalgesia.

[Expression of KCNA2 in the dorsal root ganglia of rats with osteoarthritis pain induced by monoiodoacetate]

OBJECTIVE

To investigate the changes in the expression of voltage-gated potassium channel subunit KCNA2 in the dorsal root ganglion (DRG) neurons of rats with osteoarthritis (OA) pain induced by sodium monoiodoacetate and explore the mechanism.

METHODS

A total of 156 adult male Sprague-Dawley rats were randomly divided into blank control group, saline group and intra-articular monoiodoacetate injection-induced OA group. The paw withdrawal mechanical threshold (PWMT) was measured before and at 1, 2, 4, and 6 weeks after monoiodoacetate injection. At 4 weeks after the injection, the pathological changes in the knee joints were analyzed using HE staining and Safranin O-Fast Green staining, and the expression of activating transcription factor 3 (ATF-3) and inducible nitric oxide synthase (iNOS) in the DRG neurons were detected by immunofluorescence staining. The expression of Kcna2 mRNA in the DRG neurons was detected by RT-qPCR at 1, 2, 4 and 6 weeks after the injection. The expression of KCNA2 in the DRG was measured by Western blotting, and the methylation level of Kcna2 promoter region was measured by MSPCR at 4 weeks after the injection.

RESULTS

The PWMT of the rats in OA group was significantly decreased at 2, 4, and 6 weeks after the injection as compared with the baseline (P &lt; 0.05 or P &lt; 0.001) as well as the control group (P &lt; 0.05 or P &lt; 0.001). Four weeks after the intra-articular injection, fractures and defects on the surface of the articular cartilage, bone hyperplasia, and blurred tidal line were observed in the rats in OA group, but no obvious pathological changes were detected in the control or saline groups. Compared with those in the control group, the expressions of ATF-3 and iNOS were significantly increased (P &lt; 0.01) at 4 weeks after injection; the expression of Kcna2 mRNA at 2, 4 and 6 weeks and the expression of KCNA2 protein at 4 weeks were all significantly decreased (P &lt; 0.05 or P &lt; 0.01), and the methylation level of Kcna2 gene was significantly increased at 4 weeks after the injection in OA group (P &lt; 0.01).

CONCLUSIONS

The expression of KCNA2 is decreased in the DRG neurons of rats with OA pain likely as a result of enhanced methylation of Kcna2 promoter region.

Patients With Knee Osteoarthritis Who Score Highly on the PainDETECT Questionnaire Present With Multimodality Hyperalgesia, Increased Pain, and Impaired Physical Function

OBJECTIVES

PainDETECT is a self-report questionnaire that can be used to identify features of neuropathic pain. A proportion of patients with knee osteoarthritis (OA) score highly on the PainDETECT questionnaire. This study aimed to determine whether those with a higher "positive neuropathic" score on the PainDETECT questionnaire also had greater pain, hypersensitivity, and reduced function compared with individuals with knee OA with lower PainDETECT scores.

MATERIALS AND METHODS

In total, 130 participants with knee OA completed the PainDETECT, Western Ontario and McMaster Universities Arthritis Index (WOMAC), and Pain Quality Assessment Scale questionnaires. Quantitative sensory testing was carried out at 3 sites (both knees and elbow) using standard methods. Cold and heat pain thresholds were tested using a Peltier thermode and pressure pain thresholds using a digital algometer. Physical function was assessed using 3 timed locomotor function tests.

RESULTS

In total, 22.3% of participants scored in the "positive neuropathic" category with a further 35.4% in the unclear category. Participants in the "positive neuropathic" category reported higher levels of pain and more impaired function based on the WOMAC questionnaire (P<0.0001). They also exhibited increased levels of hyperalgesia at the knee and upper limb sites for all stimulation modalities except heat pain thresholds at the OA knee. They were also slower to complete 2 of the locomotion tasks.

DISCUSSION

This study identified a specific subgroup of people with knee OA who exhibited PainDETECT scores in the "positive neuropathic" category. These individuals experienced increased levels of pain, widespread, multimodality hyperalgesia, and greater functional impairment than the remaining cohort. Identification of OA patients with this pain phenotype may permit more targeted and effective pain management.