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Background: The treatment of osteoarthritis with knee replacement aims to reduce pain and disability. However, some people experience chronic pain. Objectives: To improve outcomes for people with chronic pain after knee replacement by identifying post-surgical predictors and effective interventions, characterising patient pathways and resource use, developing and evaluating a new care pathway, and exploring non-use of services. Design: The programme comprised systematic reviews, national database analyses, a cohort study, intervention development, a randomised controlled trial, health economic analyses, qualitative studies and stakeholder engagement. Extensive and meaningful patient and public involvement underpinned all studies. Setting: NHS, secondary care, primary care. Participants: People with, or at risk of, chronic pain after knee replacement and health-care professionals involved in the care of people with pain. Interventions: A care pathway for the management of people with pain at 3 months after knee replacement. Main outcome measures: Patient-reported outcomes and cost-effectiveness over 12 months. Data sources: Literature databases, the National Joint Registry, Hospital Episode Statistics, patient- reported outcomes, the Clinical Practice Research Datalink, the Clinical Outcomes in Arthroplasty Study, the Support and Treatment After joint Replacement randomised trial, interviews with 90 patients and 14 health-care professionals, and stakeholder events. Review methods: Systematic reviews of cohort studies or randomised trials, using meta-analysis or narrative synthesis. Results: In the Clinical Outcomes in Arthroplasty Study cohort, 14% of people experienced chronic pain 1 year after knee replacement. By 5 years, 65% reported no pain, 31% fluctuated and 4% remained in chronic pain. People with chronic pain had a worse quality of life, higher primary care costs, and more frequent analgesia prescriptions, particularly for opioids, than those not in chronic pain. People with chronic pain after knee replacement who made little or no use of services often felt nothing more could be done, or that further treatments may have no benefit or cause harm. People described a feeling of disconnection from their replaced knee. Analysis of UK databases identified risk factors for chronic pain after knee replacement. Pre- operative predictors were mild knee pain, smoking, deprivation, body mass index between 35 and 40 kg/m2 and knee arthroscopy. Peri- and post-operative predictors were mechanical complications, infection, readmission, revision, extended hospital stay, manipulation under anaesthetic and use of opioids or antidepressants. In systematic reviews, pre-operative exercise and education showed no benefit in relation to chronic pain. Peri-operative interventions that merit further research were identified. Common peri- operative treatments were not associated with chronic pain. There was no strong evidence favouring specific post-operative physiotherapy content. We evaluated the Support and Treatment After joint Replacement care pathway in a multicentre randomised controlled trial. We randomised 363 people with pain at 3 months after knee replacement from eight NHS Trusts in England and Wales. At 12 months’ follow-up, the intervention group had lower mean pain severity (adjusted difference –0.65, 95% confidence interval –1.17 to -0.13; p = 0.014) and pain interference (adjusted difference –0.68, 95% confidence interval –1.29 to -0.08; p = 0.026), as measured on the Brief Pain Inventory subscales (scale 0–10). People receiving the Support and Treatment After joint Replacement pathway had lower NHS and Personal Social Services costs (–£724, 95% confidence interval –£150 to £51) and higher quality-adjusted life-years (0.03, 95% confidence interval –0.008 to 0.06) than those with usual care. The Support and Treatment After joint Replacement pathway was cost-effective with an incremental net monetary benefit at the £20,000 per quality-adjusted life-year threshold of £1256 (95% confidence interval £164 to £2348), indicating a 98.79% probability that the intervention is the cost-effective option. Participants found the Support and Treatment After joint Replacement pathway acceptable, with opportunities to receive information and discuss concerns while ensuring further treatment and support. In systematic reviews considering treatments for chronic pain after surgery we identified some unifactorial interventions that merit further research after knee replacement. Health-care professionals delivering and implementing the Support and Treatment After joint Replacement pathway valued its focus on neuropathic pain and psychosocial issues, enhanced patient care, formalised referrals, and improved pain management. Stakeholders supported pathway implementation. Limitations: Database analyses were limited to factors recorded in data sets. Pain was only measured 6 months after surgery. However, analyses including large numbers of centres and patients should be generalisable across the NHS. In many studies found in systematic reviews, long-term pain was not a key outcome. Conclusions: The Support and Treatment After joint Replacement pathway is a clinically effective and cost-effective, acceptable intervention for the management of chronic pain after knee replacement. Unifactorial interventions merit further study before inclusion in patient care. People with pain should be empowered to seek health care, with the support of health-care professionals. Future work: Future work should include research relating to the implementation of the Support and Treatment After joint Replacement pathway into the NHS, an assessment of its long-term clinical effectiveness and cost-effectiveness and wider application, and an evaluation of new interventions for incorporation in the pathway. It will also be important to design and conduct research to improve communication between patients and health-care professionals before surgery; explore whether or not education and support can enable earlier recognition of chronic pain; consider research that may identify how to support people’s feelings of disconnectedness from their new knee; and design and evaluate a pre-surgical intervention based on risk factors. Study registration: All systematic reviews were registered on PROSPERO (CRD42015015957, CRD42016041374 and CRD42017041382). The Support and Treatment After joint Replacement randomised trial was registered as ISRCTN92545361. Funding: This project was funded by the National Institute for Health and Care Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 11, No. 3. See the NIHR Journals Library website for further project information.

Retraction Watch data are available from The Center For Scientific Integrity, the parent nonprofit organization of Retraction Watch, subject to a standard data use agreement. Retraction is a mechanism for correcting the scientific record and alerts readers when a study contains unreliable or flawed data. Such data may arise from error or research misconduct. Studies examining the landscape of retracted publications provide insight into the extent of unreliable data and its effect on a medical discipline. We aimed to explore the extent and characteristics of retracted publications in pain research. We searched the EMBASE, PubMed, CINAHL, PsycINFO and Retraction Watch databases to 31 December 2022. We included retracted articles that (i) investigated mechanisms of painful conditions, (ii) tested treatments that aimed to reduce pain, or (iii) measured pain as an outcome. Descriptive statistics were used to summarise the included data. We included 389 pain articles published between 1993 and 2022 and retracted between 1996 and 2022. There was a significant upward trend in the number of retracted pain articles over time. Sixty-six percent of articles were retracted for reasons relating to misconduct. The median (interquartile range) time from article publication to retraction was 2 (0.7 to 4.3) years. The time to retraction differed by reason for retraction, with data problems, comprising data falsification, duplication, and plagiarism, resulting in the longest interval (3 (1.2 to 5.2) years). Further investigations of retracted pain articles, including exploration of their fate post-retraction, are necessary to determine the impact of unreliable data on pain research.

The President of the International Association for the Study of Pain established a task force on cannabis and cannabinoid analgesia to systematically examine the evidence on (1) analgesic pharmacology of cannabinoids and preclinical evidence on their efficacy in animal models of injury-related or pathological persistent pain; (2) the clinical efficacy of cannabis, cannabinoids, and cannabis-based medicines for pain; (3) harms related to long-term use of cannabinoids; as well as (4) societal issues and policy implications related to the use of these compounds for pain management. Here, we summarize key knowledge gaps identified in the task force outputs and propose a research agenda for generating high-quality evidence on the topic. The systematic assessment of preclinical and clinical literature identified gaps in rigor of study design and reporting across the translational spectrum. We provide recommendations to improve the quality, rigor, transparency, and reproducibility of preclinical and clinical research on cannabis and cannabinoids for pain, as well as for the conduct of systematic reviews on the topic. Gaps related to comprehensive understanding of the endocannabinoid system and cannabinoid pharmacology, including pharmacokinetics and drug formulation aspects, are discussed. We outline key areas where high-quality clinical trials with cannabinoids are needed. Remaining important questions about long-term and short-term safety of cannabis and cannabinoids are emphasized. Finally, regulatory, societal, and policy challenges associated with medicinal and nonmedicinal use of cannabis are highlighted, with recommendations for improving patient safety and reducing societal harms in the context of pain management.

Pain signals the presence of potential harm, captures attention, and can inhibit performance on concurrent tasks. What is less well known, however, is whether such attentional capture also occurs in a wider social context, such as when observing people in pain. In order to explore this possibility, we adopted a novel social-cue detection methodology: the bodies-in-the-crowd task. Two experiments are reported that consider whether nonverbal cues of pain, happiness and anger as expressed through body postures would capture and hold attention. Both experiments recruited 40 (20 male, 20 female) pain-free individuals. Overall, results show that pain postures do not capture attention any more than happiness or anger postures, but disengagement from pain postures was significantly slower across both studies. Gender differences were also found, and were more likely to be found, when crowds comprised both men and women. Male pain postures were more likely to capture attention. Whilst female observers had faster target detection speed, and were quicker to disengage from distractors. They also showed slower disengagement from female expressions overall. Male observers showed no variation based on target or distractor gender. Implications and potential directions for future research are discussed.

This study considered the attentional functioning of adolescents with varying levels of pain catastrophizing. Specifically, we investigated the relationship between pain catastrophizing and attention bias to pain facial expressions. Furthermore, drawing on dual process models in the context of pain, we investigated the moderating role of attention control on this relationship. Adolescents (N = 73; age, 16-18 years) performed a dot-probe task in which facial expressions of pain and neutral expressions were presented for 100 milliseconds and 1250 milliseconds. Participants also completed self-report pain catastrophizing and attention control measures. We found that although there was no main effect of pain catastrophizing on attention bias towards pain faces, attention control did significantly moderate this relationship. Further analysis revealed that lower levels of attention control were significantly associated with increasing attentional vigilance towards pain faces only within high catastrophizing adolescents. In addition, we found that poorer attention control was related to increased attention bias for pain faces (regardless of pain catastrophizing level) when these faces were presented for relatively longer durations (ie, 1250 milliseconds) but not for short durations (ie, 100 milliseconds). This study supports a dual process model of attentional processes in pain, thus replicating previous findings within the psychopathology literature but extending them to the study of pain. Theoretical and clinical implications of our findings are discussed.