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

Unravelling relationships between obesity, diabetes, and factors related to somatosensory functioning in knee osteoarthritis patients

OBJECTIVE

This study explores the association between obesity, diabetes, and somatosensory functioning in patients with knee osteoarthritis (OA), aiming to understand how metabolic conditions are related to pain mechanisms in this patient population. We hypothesized that higher body mass index (BMI), fat mass, and glycated hemoglobin levels (HbA1c) are associated with signs of altered somatosensory functioning.

METHODS

A cross-sectional analysis was conducted as part of a larger multicentre prospective cohort study. Data were collected from patients awaiting total knee arthroplasty in Belgium and the Netherlands. Associations between BMI, fat mass, HbA1c, and various pain-related variables were examined employing Pearson and Spearman correlation analyses which were further analyzed with linear regression techniques.

RESULTS

The study included 223 participants. Analysis revealed a significant although weak negative correlation between fat mass and pressure pain thresholds (PPT) at multiple locations, suggesting a link between higher fat mass and increased mechanical hyperalgesia. There were no significant correlations between BMI and pain-related outcomes. HbA1c levels showed very weak positive correlations with pain measures but did not withstand correction for multiple testing.

CONCLUSION

The findings indicate that fat mass may be closely associated with altered somatosensory functioning in patients with knee OA. However, no significant correlations were found between BMI or HbA1c levels and pain-related outcomes. Future research should focus on longitudinal studies to elucidate the causal relationships and further explore the impact of metabolic factors on pain mechanisms in this patient population. Key Points • The findings indicate that fat mass may be closely associated with altered somatosensory functioning in patients with knee OA.

Online Learning to Improve Nurses' Knowledge, Attitudes, and Self-Efficacy About Managing Postoperative Pain in Older Adults

BACKGROUND

Older adults undergoing total knee arthroplasty may develop chronic pain without effective postoperative pain management. Increasing nurses' knowledge, changing their attitudes, and developing their pain management self-efficacy could improve the effectiveness of pain management.

AIM

To determine the effectiveness of an online learning program to help registered nurses to manage postoperative pain in older adults undergoing total knee arthroplasty.

DESIGN

A quasi-experimental pre-test-post-test design with intervention and control groups.

METHOD

Six inpatient units were randomly selected at a large tertiary care medical center. Sixty nurses were evenly divided between intervention and control groups to participate in online learning about postoperative pain management in patients undergoing total knee arthroplasty. The content was based on Kolb's experiential learning theory. Data were collected on nurses' knowledge and attitudes toward pain management and pain management self-efficacy at baseline and after completion. Data were analyzed using descriptive statistics, chi-square tests, paired t-tests, and independent t-tests.

RESULTS

The knowledge and attitudes about pain management and pain management self-efficacy toward older adults undergoing total knee arthroplasty of nurses in the intervention group significantly improved compared to the baseline and were also significantly higher than in the control group.

CONCLUSIONS

An online learning program improves nurses' understanding and ability to manage pain in older adults undergoing total knee arthroplasty. This was therefore an effective learning method.

Does pain tolerance mediate the effect of physical activity on chronic pain in the general population? The Tromsø Study

ABSTRACT

Knowledge is needed regarding mechanisms acting between physical activity (PA) and chronic pain. We investigated whether cold pain tolerance mediates an effect of leisure-time physical activity on the risk of chronic pain 7 to 8 years later using consecutive surveys of the population-based Tromsø Study. We included participants with information on baseline leisure-time PA (LTPA) and the level of cold pressor-assessed cold pain tolerance, who reported chronic pain status at follow-up as any of the following: chronic pain for ≥3 months, widespread chronic pain, moderate-to-severe chronic pain, or widespread moderate-to-severe chronic pain. We included 6834 participants (52% women; mean age, 55 years) in counterfactual mediation analyses. Prevalence decreased with severity, for example, 60% for chronic pain vs 5% for widespread moderate-to-severe chronic pain. People with one level higher LTPA rating (light to moderate or moderate to vigorous) at baseline had lower relative risk (RR) of 4 chronic pain states 7 to 8 years later. Total RR effect of a 1-level LTPA increase was 0.95 (0.91-1.00), that is, -5% decreased risk. Total effect RR for widespread chronic pain was 0.84 (0.73-0.97). Indirect effect for moderate-to-severe chronic pain was statistically significant at RR 0.993 (0.988-0.999); total effect RR was 0.91 (0.83-0.98). Statistically significantly mediated RR for widespread moderate-to-severe chronic pain was 0.988 (0.977-0.999); total effect RR was 0.77 (0.64-0.94). This shows small mediation of the effect of LTPA through pain tolerance on 2 moderate-to-severe chronic pain types. This suggests pain tolerance to be one possible mechanism through which PA modifies the risk of moderate-to-severe chronic pain types with and without widespread pain.

Transcranial Direct Current Stimulation Attenuates the Chronic Pain of Osteoarthritis in Rats via Reducing NMDAR2B Expressions in the Spinal Cord

OBJECTIVES

Osteoarthritis (OA) has been the common cause to lead to chronic pain. Transcranial direct current stimulation (tDCS) is effective in the treatment of chronic pain, but its analgesic mechanism is still unclear. This study observed the analgesic effects of tDCS in rats to explore the top-down analgesic modulation mechanism of tDCS.

METHODS

Monosodium iodoacetate (MIA) was used to establish OA chronic pain model. After 21 days, the rats received tDCS for 14 consecutive days (20 min/day). We assessed the pain-related behaviors of rats at different time points. Western blot and Immunohistochemistry were performed to observe the expression level of NMDAR2B in the spinal cord after tDCS treatment.

RESULTS

After MIA injection, rats developed apparent mechanical hyperalgesia and thermal hyperalgesia. However, the pain-related behaviors of rats were significantly improved after tDCS treatment. In addition, the expression of NMDAR2B and the proportion of positive stained cells of NMDAR2B were reversed by tDCS treatment.

CONCLUSIONS

The results demonstrated that tDCS can attenuate OA-induced chronic pain in rats via reducing NMDAR2B expressions in the spinal cord. We believe that this may be the result of tDCS participating in the top-down modulation of pain pathway in the endogenous analgesic system.

Prognostic Factors for Postoperative Chronic Pain after Knee or Hip Replacement in Patients with Knee or Hip Osteoarthritis: An Umbrella Review

Knee and hip osteoarthritis are highly prevalent in the older population. Management of osteoarthritis-related pain includes conservative or surgical treatment. Although knee or hip joint replacement is associated with positive outcomes, up to 30% of patients report postoperative pain in the first two years. This study aimed to synthesize current evidence on prognostic factors for predicting postoperative pain after knee or hip replacement. An umbrella review of systematic reviews was conducted to summarize the magnitude and quality of the evidence for prognostic preoperative factors predictive of postoperative chronic pain (>6 months after surgery) in patients who had received knee or hip replacement. Searches were conducted in MEDLINE, CINAHL, PubMed, PEDro, SCOPUS, Cochrane Library, and Web of Science databases from inception up to 5 August 2022 for reviews published in the English language. A narrative synthesis, a risk of bias assessment, and an evaluation of the evidence confidence were performed. Eighteen reviews (nine on knee surgery, four on hip replacement, and seven on both hip/knee replacement) were included. From 44 potential preoperative prognostic factors, just 20 were judged as having high or moderate confidence for robust findings. Race, opioid use, preoperative function, neuropathic pain symptoms, pain catastrophizing, anxiety, other pain sites, fear of movement, social support, preoperative pain, mental health, coping strategies, central sensitization-associated symptoms, and depression had high/moderate confidence for an association with postoperative chronic pain. Some comorbidities such as heart disease, stroke, lung disease, nervous system disorders, and poor circulation had high/moderate confidence for no association with postoperative chronic pain. This review has identified multiple preoperative factors (i.e., sociodemographic, clinical, psychological, cognitive) associated with postoperative chronic pain after knee or hip replacement. These factors may be used for identifying individuals at a risk of developing postoperative chronic pain. Further research can investigate the impact of using such prognostic data on treatment decisions and patient outcomes.

No Evidence for Cognitive Impairment in an Experimental Rat Model of Knee Osteoarthritis and Associated Chronic Pain

Although chronic pain states have been associated with impaired cognitive functions, including memory and cognitive flexibility, the cognitive effects of osteoarthritis (OA) pain remain to be clarified. The aim of this study was to measure cognitive function in the mono-iodoacetate (MIA) rat model of chronic OA-like knee pain. We used young adult male Lister hooded rats, which are well-suited for cognitive testing. Rats received either a unilateral knee injection of MIA (3 mg/50 µL) or saline as control. Joint pain at rest was assessed for up to 12 weeks, using weight-bearing asymmetry, and referred pain at a distal site, using determination of hindpaw withdrawal thresholds. The watermaze delayed-matching-to-place test of rapid place learning, novel object recognition memory assay, and an operant response-shift and -reversal task were used to measure memory and behavioral flexibility. Open-field locomotor activity, startle response, and prepulse inhibition were also measured for comparison. MIA-injected rats showed markedly reduced weight-bearing on the injured limb, as well as pronounced cartilage damage and synovitis, but interestingly no changes in paw withdrawal threshold. Rearing was reduced, but otherwise, locomotor activity was normal and no changes in startle and prepulse inhibition were detected. MIA-injected rats had intact watermaze delayed-matching-to-place performance, suggesting no substantial change in hippocampal function, and there were no changes in novel object recognition memory or performance on the operant task of behavioral flexibility. Our finding that OA-like pain does not alter hippocampal function, unlike other chronic pain conditions, is consistent with human neuroimaging findings. PERSPECTIVE: Young adult rats with OA-like knee pain showed no impairments in hippocampal memory function and behavioral flexibility, suggesting that OA pain impacts cognitive functions less than other chronic pain conditions. In patients, OA pain may interact with other factors (e.g., age, socio-economic factors, and medication) to impair cognition.

Assessment of Pain in Osteoarthritis of the Knee

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

Efficacy of Perilla frutescens (L.) Britton var. frutescens extract on mild knee joint pain: A randomized controlled trial

Objectives: This study aimed to evaluate the clinical efficacy and safety of PE extracts developed for the purpose of relieving pain and improving knee joint function on semi-healthy people with mild knee joint pain.

Methods: A randomized, double-blind, two-arm, single-center, placebo-controlled clinical trial was conducted. Individuals with knee joint pain and a visual analogue scale (VAS) score < 50 mm were included in the study, and participants with radiological arthritis were excluded. Participants were administered either PFE or a placebo capsule (700 mg, twice a day) orally for eight weeks. The comparisons of the changed VAS score and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) scores between the PFE and placebo groups were primary outcomes, while the five inflammation-related laboratory tests including cartilage oligomeric matrix protein, cyclooxygenase-2, neutrophil and lymphocyte ratio, high sensitive C-reactive protein, and erythrocyte sedimentation rate were secondary outcomes. Also, a safety assessment was done.

Results: Eighty participants (mean age, 38.4 ± 14.0, male: female, 28:52) were enrolled; 75 completed the trial (PFE 36 and placebo 39). After eight weeks, both VAS and WOMAC scores were reduced in the PFE and placebo groups. The changed scores were significantly higher in the PFE group compared to the placebo group: 19.6 ± 10.9 vs. 6.8 ± 10.5; VAS scores (p < 0.001), and 20.5 ± 14.7 vs. 9.3 ± 16.5; total WOMAC scores (p < 0.01) including the sub-scores for pain, stiffness, and functions. No significant changes were reported in the five inflammation-related laboratory parameters. All adverse events were considered minor and unlikely to result from the intervention.

Conclusion: Eight weeks of PFE intake was more effective than placebo in reducing knee joint pain and improving knee joint function in sub-healthy people with mild knee joint pain, and there were no major safety concerns.

Clinical Trial Registration:https://cris.nih.go.kr/cris/search/detailSearch.do?search_lang=E&focus=reset_12&search_page=M&pageSize=10&page=undefined&seq=23101&status=5&seq_group=19745, identifier CRIS: KCT0007219

The Minimal Clinically Important Difference Changes Greatly Based on the Different Calculation Methods

BACKGROUND

The minimal clinically important difference (MCID) for patient-reported outcome measures (PROMs) expresses both the extent of the improvement and the value that patients place on it. MCID use is becoming increasingly widespread to understand the clinical efficacy of a given treatment, define guidelines for clinical practice, and properly interpret trial results. However, there is still large heterogeneity in the different calculation methods.

PURPOSE

To calculate and compare the MCID threshold values of a PROM by applying various methods and analyzing their effect on the study results interpretation.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 3.

METHODS

The data set used to investigate the different MCID calculation approaches was based on a database of 312 patients affected by knee osteoarthritis and treated with intra-articular platelet-rich plasma. MCID values were calculated on the International Knee Documentation Committee (IKDC) subjective score at 6 months using 2 approaches: 9 methodologies referred to an anchor-based approach and 8 methodologies to a distribution-based approach. The obtained threshold values were applied to the same series of patients to understand the effect of using different MCID methods in evaluating patient response to treatment.

RESULTS

The different methods employed led to MCID values ranging from 1.8 to 25.9 points. The anchor-based methods ranged from 6.3 to 25.9, while the distribution-based ones were from 1.8 to 13.8 points, showing a 4.1× variation of the MCID values within the anchor-based methods and a 7.6× variation within the distribution-based methods. The percentage of patients who reached the MCID for the IKDC subjective score changed based on the specific calculation method used. Among the anchor-based methods, this value varied from 24.0% to 66.0%, while among the distribution-based methods, the percentage of patients reaching the MCID varied from 44.6% to 75.9%.

CONCLUSION

This study proved that different MCID calculation methods lead to highly heterogeneous values, which significantly affect the percentage of patients achieving the MCID in a given population. The wide-ranging thresholds obtained with the different methodologies make it difficult to evaluate the real effectiveness of a given treatment questioning the usefulness of MCID, as currently available, in the clinical research.

Multiple Injections of Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Current Evidence in Randomized Controlled Trials

In recent years, various clinical trials have focused on treating knee osteoarthritis (KOA) with multiple injections of platelet-rich plasma (PRP). However, compared with the multiple hyaluronic acid (m-HA) injections, the clinical efficacy of multiple PRP (m-PRP) injections for KOA still remains controversial among these studies. Therefore, we aimed to compare the clinical effectiveness of m-PRP injections with m-HA injections in the treatment of KOA in this systematic review. Relevant clinical trials were searched via bibliographic databases, including Medline, PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials, to compare the m-PRP and m-HA injections in the treatment of KOA. Finally, fourteen randomized controlled trials, including 1512 patients, showed the postoperative VAS, WOMAC, IKDC, or EQ-VAS scores and were enrolled in this systematic review. Compared with the group of intra-articular m-HA injections, the group of intra-articular m-PRP injections was lower in the VAS scores at 3-month (WMD = −0.25; 95%CI, −0.40 to −0.10, p = 0.0009) and 12-month (WMD = −0.64; 95%CI, −0.79 to −0.49, p < 0.00001) follow-ups. In addition, the group of intra-articular m-PRP injections was also lower in the WOMAC scores at 1-month (WMD = −1.23; 95%CI, −2.17 to −0.29, p = 0.01), 3-month (WMD = −5.34; 95%CI, −10.41 to −0.27, p = 0.04), 6-month (WMD = −11.02; 95%CI, −18.09 to −3.95, p = 0.002), and 12-month (WMD = −7.69; 95%CI, −12.86 to −2.52, p = 0.004) follow-ups. Furthermore, compared with the group of intra-articular m-HA injections, the group of intra-articular m-PRP injections was higher in the IKDC scores at 3-month (WMD = 7.45; 95%CI, 2.50 to 12.40, p = 0.003) and 6-month (WMD = 5.06; 95%CI, 1.94 to 8.18, p = 0.001) follow-ups. However, the long-term adverse side of m-PRP injections for KOA still needs more large-scale trials and long-term follow-ups.

Predictive Value of Pain Sensitization Associated with Response to Exercise Therapy in Patients with Knee Osteoarthritis: A Prospective Cohort Study

PURPOSE

Knee osteoarthritis (KOA) is a degenerative disease with inflammation, becoming persistent as it progresses, resulting in reduced quality of life. Exercise is the recommended treatment for KOA; however, the extent of pain reduction with exercise is heterogeneous and the prognostic implications of baseline factors in patients undergoing exercise are still unknown. This study examined the association between the response to exercise therapy and clinical outcomes, radiologic severity, and pain sensitization, and investigated the optimal predictive value for the effectiveness of exercise.

PATIENTS AND METHODS

Demographics, radiologic severity, pressure pain threshold (PPT), and temporal summation of pain (TSP) at the knee, tibia, and forearm were assessed at baseline. The pain numeric rating scale (NRS) was assessed before and after 12 weeks of exercise. Patients were divided into responder/non-responder groups according to recommended criteria: responder, ≥30% reduction in pain; non-responder, <30% reduction in pain, and each variable was compared between the groups. The area under the curve (AUC) and cutoff points were determined by receiver operating characteristic curve analysis.

RESULTS

Sixty-five patients were categorized as responders and 26 as non-responders. In the non-responder group, baseline NRS (P<0.01), pain duration (P<0.01), and TSP at the knee (P<0.001) and tibia (P<0.05) were significantly higher, and PPT at the knee (P<0.001), tibia (P<0.001), and forearm (P<0.001) were significantly lower, than those in the responder group; however, no significant differences between groups were found in other demographics and radiologic severity. The variables that showed moderate or better predictive ability (AUC≥0.7) were PPT at the knee (cutoff points: 241.5 kPa), tibia (307.5 kPa), forearm (318.5 kPa), and TSP at the knee (15.5 mm).

CONCLUSION

Our findings suggest that pain sensitization is associated with the response to exercise therapy. Furthermore, we provide clinically predictive values for PPT and TSP in predicting the outcome to exercise in KOA.