Fundamentals of osteoarthritis: outcome evaluation with patient-reported measures and functional tests

Expanding the ABCC-tool for osteoarthritis: Development and content validation

Objective

Osteoarthritis (OA) care should be more person-centered based on physical, emotional and social aspects, instead of the current stepped-care approach solely based on physical symptoms, according to OA patients. By developing a novel module for OA in the Assessment of Burden of Chronic Condition (ABCC)-tool, a tool based on these three aspects, experienced quality of OA care and shared-decision making are expected to improve.

Design

The development of the novel OA module involved a triangular iterative process, interviewing OA patients and healthcare professionals in the field of OA, an expert panel and a literature search to identify the needs to improve OA care. Patients provided feedback on the first version of the OA module, leading to a second version. This second version was used to evaluate content validity. OA patients and healthcare professionals in the field of OA were asked to evaluate relevance, comprehensiveness and comprehensibility, based on the COSMIN methodology. For healthcare professionals, the item-content validity index (I-CVI) was calculated.

Results

The module includes questions about pain, kinesiophobia and joint stiffness. For all three questions, 94% of the patients found these questions important for patients with OA. The I-CVI scores of the healthcare professionals ranged from 1.0 (pain, kinesiophobia) to 0.75 (joint stiffness).

Conclusion

A novel, condition-specific OA module is developed for the ABCC-tool, as a supplement to the generic questions. The module includes three questions, to measure OA specific complaints. This novel module is intended to make the ABCC-tool more elaborate and useable for a larger population.

Assessing the Value of Imaging Data in Machine Learning Models to Predict Patient-Reported Outcome Measures in Knee Osteoarthritis Patients

Knee osteoarthritis (OA) affects over 650 million patients worldwide. Total knee replacement is aimed at end-stage OA to relieve symptoms of pain, stiffness and reduced mobility. However, the role of imaging modalities in monitoring symptomatic disease progression remains unclear. This study aimed to compare machine learning (ML) models, with and without imaging features, in predicting the two-year Western Ontario and McMaster Universities Arthritis Index (WOMAC) score for knee OA patients. We included 2408 patients from the Osteoarthritis Initiative (OAI) database, with 629 patients from the Multicenter Osteoarthritis Study (MOST) database. The clinical dataset included 18 clinical features, while the imaging dataset contained an additional 10 imaging features. Minimal Clinically Important Difference (MCID) was set to 24, reflecting meaningful physical impairment. Clinical and imaging dataset models produced similar area under curve (AUC) scores, highlighting low differences in performance AUC < 0.025). For both clinical and imaging datasets, Gradient Boosting Machine (GBM) models performed the best in the external validation, with a clinically acceptable AUC of 0.734 (95% CI 0.687-0.781) and 0.747 (95% CI 0.701-0.792), respectively. The five features identified included educational background, family history of osteoarthritis, co-morbidities, use of osteoporosis medications and previous knee procedures. This is the first study to demonstrate that ML models achieve comparable performance with and without imaging features.

Movement-evoked pain is not associated with pain at rest or physical function in knee osteoarthritis

INTRODUCTION

Knee Osteoarthritis (KOA) is mainly characterized by pain. The assessment of KOA-related pain frequently focuses on different constructs subject to sources of bias or drawbacks, as the classical Pain at Rest (PAR). Movement-evoked pain (MEP), recently defined as 'pain during walking', emerges as a differential concept, since PAR and MEP are driven by different underlying mechanisms. Given the novelty of the MEP approach, its association with PAR or with different performance-based tests has not been studied in KOA yet.

MATERIALS AND METHODS

A cross sectional study was conducted. PAR was measured, alongside the performance of four mobility tests and their corresponding MEP: Timed Up and Go Test, 10-metre Walk Test, 2-Minute Walk Test, and 6-Minute Walk Test. Association and agreement were explored for MEP versus PAR, while the correlation of the tests versus each corresponding MEP-measure was assessed.

RESULTS

Neither association nor agreement were found in the duality MEP versus PAR. Also, the lack of association between the performance of a mobility test and the perceived level of pain during the development of the test was stated.

CONCLUSION

Movement-evoked pain is neither related to pain at rest nor to functional performance in subjects affected by knee osteoarthritis. The results from our study suggest that MEP and pain at rest measure and refer to different constructs in knee osteoarthritis. The implementation of MEP as an outcome in exercise-therapy could enhance the tracking of results, as well as the development of tailored interventions under different conditions.

SIGNIFICANCE

This research elucidates the relevance of MEP, recently defined as 'pain during walking', through the analysis of its association with PAR and with functional performance (measured through four mobility tests) in knee osteoarthritis. The results from our study highlight the absence of either association or agreement between MEP and PAR, fact that supports and endorses the idea that both concepts measure and refer to different constructs in knee osteoarthritis.

Psychometric properties and domains covered by patient-reported outcome measures used in trials assessing interventions for chronic pain

OBJECTIVES

To identify the patient-reported outcome measures (PROMs) used in clinical trials assessing interventions for chronic pain, describe their psychometric properties, and the clinical domains they cover.

STUDY DESIGN AND SETTING

We identified phase 3 or 4 interventional trials: on adult participants (aged >18 years), registered in clinicaltrials.gov between January 1, 2021 and December 31, 2022, and which provided "chronic pain" as a keyword condition. We excluded diagnostic studies and phase 1 or 2 trials. In each trial, one reviewer extracted all outcomes registered and identified those captured using PROMs. For each PROM used in more than 1% of identified trials, two reviewers assessed whether it covered the six important clinical domains from the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT): pain, emotional functioning, physical functioning, participant ratings of global improvement and satisfaction with treatment, symptoms and adverse events, and participant disposition (eg, adherence to medication). Second, reviewers searched PubMed for both the initial publication and latest review reporting the psychometric properties of each PROM and assessed their content validity, structural validity, internal consistency, reliability, measurement error, hypotheses testing, criterion validity, and responsiveness using published criteria from the literature.

RESULTS

In total, 596 trials assessing 4843 outcomes were included in the study (median sample size 60, interquartile range 40-100). Trials evaluated behavioral (22%), device-based (21%), and drug-based (10%) interventions. Of 495 unique PROMs, 55 were used in more than 1% trials (16 were generic pain measures; 8 were pain measures for specific diseases; and 30 were measures of other symptoms or consequences of pain). About 50% PROMs had more than 50% of psychometric properties rated as sufficient. Scales often focused on a single clinical domain. Only 25% trials measured at least three clinical domains from IMMPACT.

CONCLUSION

Half of PROMs used in trials assessing interventions for chronic pain had sufficient psychometric properties for more than 50% of criteria assessed. Few PROMs assessed more than one important clinical domain. Only 25% of trials measured more than 3/6 clinical domains considered important by IMMPACT.

Are the Effects of Resistance Exercise on Pain and Function in Knee and Hip Osteoarthritis Dependent on Exercise Volume, Duration, and Adherence? A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of this study was to determine dose parameters for resistance exercise associated with improvements in pain and physical function in knee and hip osteoarthritis (OA) and whether these improvements were related to adherence.

METHODS

We searched six databases, from inception to January 28, 2023, for randomized controlled trials comparing land-based, resistance exercise-only interventions with no intervention, or any other intervention. There were four subgroups of intervention duration: 0 to <3 months, 3 to 6 months, >6 to <12 months, ≥12 months. The between-group effect was calculated for immediate postintervention pain and physical function (activities of daily living [ADL] and sports/recreation [SPORT]).

RESULTS

For both knee and hip, data from 280 studies showed moderate benefit for pain, physical function ADL, and physical function SPORT in favor of interventions 3 to 6 months. For the knee, there was also a moderate benefit for physical function ADL in favor of interventions >6 to <12 months. From 151 knee and hip studies that provided total exercise volume data (frequency, time, duration), there was no association between volume with the effect size for pain and physical function. A total of 74 studies (69 knee, 5 hip) reported usable adherence data. There was no association between adherence with the effect size for pain and physical function.

CONCLUSION

In knee and hip OA, resistance exercise interventions 3 to 6 months (and for the knee >6 to <12 months) duration improve pain and physical function. Improvements do not depend on exercise volume or adherence, suggesting exercise does not require rigid adherence to a specific dose.

Comparison of ultrasound guidance with landmark guidance for symptomatic benefits in knee, hip and hand osteoarthritis: Systematic review and meta-analysis of randomised controlled trials

Introduction

More than half of the patients with moderate and severe osteoarthritis (OA) report unsatisfactory pain relief, requiring consideration of intra-articular (IA) injections as the second-line management. Ultrasound-guided IA injection has proven evidence of higher accuracy in administering IA injectates into the joints than landmark-guided or blind IA injections. However, questions remain about translating higher accuracy rates of ultrasound-guided injection into better clinical improvements. Therefore, we examined the symptomatic benefits (pain, function and patient satisfaction) of ultrasound-guided injection in knee, hip and hand OA compared with blind injections by synthesising a systematic review and meta-analysis of randomised controlled trials (RCT).

Methods

PubMed, Medline and Embase databases were searched for eligible studies from their inception to August 28, 2023.

Results

Out of 295 records, our meta-analysis included four RCTs (338 patients with knee OA), demonstrating significant improvement in procedural pain [-0.89 (95% CI -1.25, -0.53)], pain at follow-up [-0.51 (95% CI -0.98, -0.04)] and function [1.30 (95% CI 0.86, 1.73)], favouring ultrasound guidance. One single study showed higher patient satisfaction with ultrasound guidance.

Conclusion

Ultrasound-guided IA injection provided superior clinical outcomes compared with landmark-guided IA injection.

Allogeneic umbilical cord blood-derived mesenchymal stem cell implantation versus microdrilling combined with high tibial osteotomy for cartilage regeneration

This study compared cartilage regeneration outcomes in knee osteoarthritis (OA) using allogeneic human umbilical cord blood-derived mesenchymal stem cell (hUCB-MSC) implantation and microdrilling with high tibial osteotomy (HTO). Fifty-four patients (60 knees) were included: 24 (27 knees) in the hUCB-MSC group and 30 (33 knees) in the microdrilling group. Both groups showed significant improvements in pain and functional scores at 6, 12, and 24 months compared to baseline. At 24 months, the hUCB-MSC group had significantly improved scores. Arthroscopic assessment at 12 months revealed better cartilage healing in the hUCB-MSC group. In subgroup analysis according to the defect site, hUCB-MSC implantation showed superior cartilage healing for anterior lesions. In conclusion, both treatments demonstrated effectiveness for medial OA. However, hUCB-MSC implantation had better patient-reported outcomes and cartilage regeneration than microdrilling. The study suggests promising approaches for cartilage restoration in large knee defects due to OA.

The association between lipid biomarkers and osteoarthritis based on the National Health and Nutrition Examination Survey and Mendelian randomization study

To explore the association between lipid markers and osteoarthritis (OA). First, the National Health and Nutrition Examination Survey (NHANES) database was used to screen participants with lipid markers, OA and relevant covariates, and logistic regression was used to analyze the association between lipid markers and OA; Then, under the theoretical framework of Mendelian randomization (MR), two-sample MR was performed using GWAS data of lipid markers and OA to explore the causal association between the two, which was analyzed by inverse variance weighting (IVW) method. Heterogeneity test, sensitivity analysis and pleiotropy analysis were also performed. The NHANES database screened a total of 3706 participants, of whom 836 had OA and 2870 did not have OA. When lipid markers were used as continuous variables, multivariate logistic results showed an association between HDL, LDL and OA (HDL, OR (95%):1.01 (1.00, 1.01); LDL, OR (95%):1.00 (0.99, 1.00)). When lipid markers were used as categorical variables, multivariate logistic results showed the fourth quartile result of 0.713 (0.513, 0.992) for LDL relative to the first quartile. In MR study, the results of the IVW method for TG, TL, HDL and LDL showed OR (95% CI) of 1.06 (0.97-1.16), 0.95 (0.85-1.06), 0.94 (0.86-1.02) and 0.89 (0.80-0.998) with P-values of 0.21, 0.37. 013, 0.046. The heterogeneity tests and multiplicity analyses showed P-values greater than 0.05, and sensitivity analyses showed no abnormal single nucleotide polymorphisms. Through NHANES database and MR analyses, LDL was found to be a protective factor for OA, while HDL still needs further study. Our results provide new biomarkers for preventive and therapeutic strategies for OA.

Effectiveness of neuromuscular electrical stimulation training combined with exercise on patient-reported outcomes measures in people with knee osteoarthritis: A systematic review and meta-analysis

OBJECTIVE

This study examined the effectiveness of neuromuscular electrical stimulation (NMES) added to the exercise or superimposed on voluntary contractions on patient-reported outcomes measures (PROMs) in people with knee osteoarthritis (OA).

METHODS

This systematic review was described according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Randomized controlled trials (RCTs) were obtained from a systematic literature search in five electronic databases (PubMed, PEDro, LILACS, EMBASE, and SPORTDiscus) in April 2022. We described the effects of intervention according to each PROMs (scores for Pain; Self-reported functional ability; Symptoms (hear clicking, swelling, catching, restricted range of motion, and stiffness); Daily living function; Sports function; and Quality of life) and used a random-effect model to examine the impact of NMES plus exercise on pain compared with exercise in people with knee OA.

RESULTS

Six RCTs (n = 367) were included. In the qualitative synthesis, the systematic literature analysis showed improvement in pain after NMES plus exercise compared with exercise alone in three studies. The other three studies revealed no difference between groups in pain, although similar improvement after treatments. In the meta-analysis, NMES at a specific joint angle combined with exercise was not superior to exercise alone in pain management (standardized mean difference = -0.33, 95% CI = -1.05 to 0.39, p = 0.37). There was no additional effect of NMES on exercise on self-reported functional ability, stiffness, and physical function compared with exercise alone. In only one study, symptoms, activities of daily living, sports function, and quality of life improved after whole-body electrostimulation combined with exercise.

CONCLUSION

This review found insufficient evidence for the effectiveness of NMES combined with exercise in treating knee OA considering PROMs. While pain relief was observed in some studies, more high-quality clinical trials are needed to support the use of NMES added to the exercise in clinical practice. Electrical stimulation in a whole-body configuration combined with exercise shows promise as an alternative treatment option.

A scoping review of patient self-report measures of flare in knee and hip osteoarthritis (OA): A report from the OMERACT flares in OA working group

PURPOSE

We aimed to analyze the content validity/domain match and feasibility of self-report instruments that could measure flare in osteoarthritis (OA), by extending our 2017 literature review on the definition of flare in knee and hip OA.

METHOD

We searched PubMed (Medline), Web of Science and PsycInfo (Ebsco Host) databases for original articles reporting research about flare (or synonyms) in humans with knee and hip OA, between 2017 and 2023. Four experts worked independently, checking the records, and assessing content validity and feasibility, writing justification for exclusion.

RESULTS

At literature review phase, 575 papers were filtered. After experts' analysis, 59 studies were included, and 44 instruments associated with flare in OA were identified. Most were studies about pain in knee or hip OA (35 %), cultural adaptation of a measure (33 %) or studies investigating psychometric properties of full (16 %) or short form (4 %) instruments. The assessment of domain match and feasibility revealed that 15 instruments were assigned a label of 'yes' or 'uncertain' as to whether or not there was a good match with the domain concept or whether the instrument was considered feasible to use.

DISCUSSION

Most identified instruments considered different aspects of pain and the associated discomfort in performing daily activities but did not include the central aspects of flare in OA, i.e. the change of state, nor the additional Outcome Measures in Rheumatology (OMERACT) endorsed domains for OA flare namely stiffness, swelling, psychological aspects, impact of symptoms including fatigue and sleep disturbance. Although it is possible that the period specified to conduct this literature review may have led to some recognized instruments being excluded, this review demonstrates the need for the research community to reach consensus on the best way to measure self-reported flares in future clinical trials and observational studies.

Association between pyrethroid exposure and osteoarthritis: a national population-based cross-sectional study in the US

BACKGROUND

With the restriction of organophosphorus and other insecticides, pyrethroids are currently the second most-used group of insecticides worldwide due to their advantages such as effectiveness and low toxicity for mammalian. Animal studies and clinical case reports have documented associations between adverse health outcomesand exposure to pyrethroids. At present, the association between chronic pyrethroid exposure and osteoarthritis (OA) remains elusive.

METHODS

Cross-sectional data from the National Health and Nutrition Examination Survey 1999-2002 and 2007-2014 were used to explore the associations of pyrethroid exposure and OA. Urinary level of 3-phenoxybenzoic acid (3-PBA) in urine samples was used to evaluate the exposure of pyrethroid, and OA was determined on the basis of self-reported physician diagnoses. Multivariable logistic regression models were used to investigate the association between pyrethroid exposure and OA.

RESULTS

Among the 6528 participants, 650 had OA. The weighted geometric mean of urinary volume-based 3-PBA concentration were 0.45 µg/L. With adjustments for major confounders, compared to participants in the lowest quartile of urinary volume-based 3-PBA, those in the highest quartilehad higher odds of OA (odds ratio, 1.39; 95% confidence interval: 1.01, 1.92). There was no nonlinear relationship between urinary volume-based 3-PBA and OA (P for non-linearity = 0.89).

CONCLUSION

High urinary 3-PBA concentration was associated with increased OA odds in the US adults. Pyrethroid exposure in the population should be monitored regularly.

Concurrent validity of the 2-and 6-minute walk test in knee osteoarthritis

BACKGROUND

The 6-Minute Walk Test (6MWT) is frequently used for the assessment of walking distances in several conditions, as knee osteoarthritis, but it can be both time-consuming for the researcher or clinician, and exhausting of painful for the subject suffering from this condition. The objective of our study was to analyze the concurrent validity of the 2-Minute Walk Test (2MWT) for patients with knee osteoarthritis compared to the 6-Minute Walk Test (6MWT).

METHODS

Cross-sectional validation study. Scores from the 6MWT of 42 ambulatory patients affected by knee osteoarthritis were compared to those from the shorter 2MWT. An initial correlation test was used to assess correlation between both measures, and a subsequent univariate regression analysis was performed with the aim of comparing the estimated outcomes of the 6MWT versus the actual 6MWT.

RESULTS

The scores from the 2MWT and 6MWT showed excellent correlation (Pearson's correlation coefficient r = 0.976; p-value < 0.001); the predictive equation based on the scores from the 2MWT (R2 = 0.952, p-value < 0.001) estimates the 6MWT scores with a relative error of 3.23%.

CONCLUSIONS

The 2MWT may be a practical assessment tool in replacement for the 6MWT in clinical assessment due to its low burden on patients and as a means of improving efficiency in a timely manner.

Measurement properties of the short version of the Western Ontario and McMaster Universities Arthritis Index (WOMAC) for individuals with knee osteoarthritis

BACKGROUND

Assessment instruments play an essential role in the management of knee osteoarthritis. This study aimed to verify the clinimetric properties and validate the short version of WOMAC's (SV-WOMAC) knee with two domains, pain (four items) and physical function (eight items) in individuals with knee osteoarthritis (KO).

METHODS

Reliability and internal consistency Construct, criterion validity, Ceiling, and floor effects analyses were performed. In addition to the SV-WOMAC, the following instruments were used: the numerical rating scale (NRPS), International Knee Documentation Committee (IKDC), the Short Form Health Survey (SF-36), and WOMAC's original version. Spearman's correlation coefficient (rho) was used to determine the magnitude of the correlation between the AFAQ and the other instruments. Moreover, the test-retest reliability and internal consistency were assessed using the intraclass correlation coefficient (ICC) and Cronbach's alpha, respectively. In addition, standard error of measurement (SEM) and minimum detectable change (MDC) were calculated.

RESULTS

One hundred and thirteen subjects with KO were included for validity analysis, and a subsample of 53 subjects was used for test-retest reliability. Adequate reliability and internal consistency were observed with ICC ≥ 0.76, SEM ≤ 1.85, MDC ≥ 5.1, and Cronbach's alpha ≥ 0.84. Regarding construct validity, correlations greater than 0.50 were observed with the IKDC, NRPS, and functional domains of the SF-36. The SV-WOMAC showed a correlation > 0.70 with the original version and did not show ceiling and floor effects.

CONCLUSION

The SV-WOMAC knee has adequate measurement properties to analyze pain and physical function in Brazilian individuals with KO.

Repeated intra-articular injections of umbilical cord-derived mesenchymal stem cells for knee osteoarthritis: a phase I, single-arm study

INTRODUCTION

Stem cell therapy has emerged as an effective treatment for multiple diseases, and some studies also demonstrate that it may be a promising treatment for osteoarthritis (OA). However, few studies have clarified the safety of repeated intra-articular injection of human umbilical cord-derived mesenchymal stem cells (UC-MSCs). To promote its application in treating OA, we conducted an open-label trial to investigate the safety of repeated intra-articular injections of UC-MSCs.

METHODS

Fourteen patients with OA (Kellgrene-Lawrence grade 2 or 3) who received repeated intra-articular injections of UC-MSCs were evaluated in three months of follow-up. The primary outcomes were the adverse events, and the second outcomes included visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) scores and SF-12 quality of life score.

RESULTS

A total of 5 of 14 patients (35.7%) experienced transient adverse reactions, which resolved spontaneously. All patients showed some improvement in knee function limitation and pain after receiving stem cell therapy. VAS score 6.0 to 3.5, WOMAC score 26.0 to 8.5, MOCART score 42.0 to 58.0, SF-12 score 39.0 to 46.0.

CONCLUSION

Repeated intra-articular injection of UC-MSCs demonstrates safety in treating OA and does not induce serious adverse events. This treatment may transiently improve symptoms in patients with knee OA and may be a potential therapeutic option for OA.

EUROVISCO Good Practice Recommendations for a First Viscosupplementation in Patients with Knee Osteoarthritis

RATIONALE

Viscosupplementation (VS) with hyaluronic acid is widely used in the management of knee osteoarthritis. There is no clear recommendation on the decision-making to achieve VS.

DESIGN

Based on extensive research of the literature and expert opinion, the members of the EUROVISCO (European Viscosupplementation Consensus Group) task force were asked to give their degree of agreement with 60 issues, using a Delphi method.

RESULTS

The expert panel achieved unanimous agreement in favor of the following statements: It is recommended to assess pain on a visual or 10-point numeric scale before considering VS. VS can be considered for patients with pain scores between 3 and 8. A standard x-ray must be obtained before the decision of VS. If the x-ray is normal, osteoarthritis must be confirmed by MRI or computed tomography (CT) arthrogram before considering VS. The aims of VS are relieving pain, improving function, and reducing non-steroidal anti-inflammatory drug (NSAID) consumption. The use of VS must not be considered for treating an osteoarthritis flare. VS can be envisaged as a first-line pharmacological treatment in patients having a contra-indication to NSAIDs or analgesics. VS can be considered in patients with contra-indications to arthroplasty. In the case of severe comorbidities (diabetes, hypertension, gastrointestinal disorders, renal failure), VS can avoid the use of potentially dangerous treatments. VS can be considered in patients receiving antiplatelet agents, vitamin K antagonists, and direct factor Xa or thrombin inhibitors. Five other statements obtained a high level of consensus.

CONCLUSION

These recommendations, illustrated in a decision algorithm, have been established to help practitioners in the decision-making of knee VS.

Clinical aspects and outcomes in osteoarthritis

Osteoarthritis (OA) is the most prevalent type of arthritis worldwide, and its incidence significantly increases with age. It commonly affects the knees, hips, spine, big toes, and hands. OA can be identified through clinical examination, symptoms, and imaging methods. Its main symptoms include pain, stiffness, and limitations in joint movement. Examinations may reveal coarse crepitus, bony enlargement, and tenderness at the joint line. In severe cases of OA, rest pain, night pain, and deformity may occur. OA can lead to decreased physical activity, function, and quality of life due to symptoms such as pain and stiffness. To evaluate these impacts, patient-reported outcome measures (PROMs) are necessary. Various generic, disease-specific, and joint-specific PROMs have been developed and used in clinical practice to assess the outcomes of OA.

Recall Bias Affects Pain Assessment in Knee Osteoarthritis: A Pilot Study

OBJECTIVE

The objective of this study was to evaluate the recall bias of symptoms evaluation in knee osteoarthritis (OA).

DESIGN

In this multicentric pilot study, 50 patients with knee OA used a mobile App (Ecological Momentary Assessment [EMA]) to collect pain and function on two 0 to 10 numerical rating scales (NRS) 2 times a day for 2 months. At the 1-month and at the 2-month follow-up visits, patients retrospectively evaluated the mean level of pain/function of the last month. Recall bias was computed as the difference between the mean level of pain/function reported using the App and the level reported with the retrospective assessment. The correlation between the recall bias and patients' characteristics, as well as pain/function trajectories, was analyzed.

RESULTS

A statistically significant recall bias was documented with higher pain reported at 1-month with the retrospective assessment (P < 0.001). These results were confirmed also at the 2-month follow-up (P = 0.002). For function, no significant recall bias was documented. During the first and second months, 47 and 31 patients showed pain peaks, respectively. The number of pain peaks during the first month was correlated with the magnitude of the recall bias (P = 0.02).

CONCLUSIONS

The recall bias influences the retrospective self-assessment of pain at the follow-up visits and the presence of pain peaks, a common event in the patients with OA, increases the magnitude of recall bias. The EMA performed with a mobile App is a useful tool to limit the influence of recall bias in the clinical and research setting evaluation of knee OA.