Work, Osteoarthritis and joint-Replacement Questionnaire

Abstract

The Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ) is a validated, condition-specific patient-reported outcome measure (PROM) engineered to assess physical work limitations in individuals suffering from knee osteoarthritis (OA) or undergoing total knee arthroplasty (TKA). Traditional orthopedic outcome measures, such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Knee Injury and Osteoarthritis Outcome Score (KOOS), primarily emphasize activities of daily living (ADLs) and recreational pursuits, frequently failing to capture the intense biomechanical demands encountered in modern occupational settings. Developed by P. Paul F. M. Kuijer and colleagues at the Coronel Institute of Occupational Health (Amsterdam UMC), the WORQ addresses this critical evaluative gap by evaluating 13 discrete, knee-strenuous physical activities performed in the workplace over a one-week recall period.

The instrument utilizes a 5-point Likert response scale ranging from 1 (“Extreme difficulty/unable to do”) to 5 (“No difficulty”), which is converted into a standardized metric from 0 to 100, where higher scores represent superior occupational physical functioning and an absence of perceived task difficulty. Psychometric evaluations across diverse occupational cohorts demonstrate that the WORQ possesses robust measurement properties, including exceptional internal consistency (Cronbach’s alpha > .90), strong test-retest reliability (intraclass correlation coefficient [ICC] > .85), confirmed unidimensional structural validity via confirmatory factor analysis (CFA), and high responsiveness to longitudinal clinical recovery following joint arthroplasty. The WORQ serves as a pivotal assessment instrument in orthopedic surgery, occupational medicine, vocational rehabilitation, and ergonomic intervention planning.

Keywords

Work Osteoarthritis and joint-Replacement Questionnaire, WORQ, Knee Osteoarthritis, Total Knee Arthroplasty, Return to Work, Occupational Health, Patient-Reported Outcome Measure, Biomechanical Load, Ergonomics, Physical Functional Capacity, Joint Replacement

Authors

The original Dutch version of the Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ) was designed, developed, and psychometrically validated by a multi-institutional research team headed by:

• P. Paul F. M. Kuijer, PhD — Coronel Institute of Occupational Health, Amsterdam Public Health Research Institute, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands. Expertise: Ergonomics, Occupational Biomechanics, Work-related Musculoskeletal Disorders.
• S. J. (Monique) Verbeek, MD — Orthopedic Surgery & Occupational Health Collaboratory, Coronel Institute of Occupational Health, Amsterdam UMC, The Netherlands.
• Haije F. van der Molen, PhD — Coronel Institute of Occupational Health, Amsterdam Public Health Research Institute, Amsterdam UMC, The Netherlands.
• Judith K. Sluiter, PhD — Professor of Work and Health, Coronel Institute of Occupational Health, Amsterdam Public Health Research Institute, Amsterdam UMC, The Netherlands.
• In collaboration with clinical orthopedic surgeons and physical therapists from the Academic Medical Center (AMC) Amsterdam and affiliated joint reconstruction registries.

Purpose

Osteoarthritis of the knee is one of the leading drivers of chronic disability, functional decline, and premature labor market departure worldwide. With the retirement age steadily increasing across developed economies, an expanding proportion of working-age adults undergo non-operative therapy or surgical intervention—notably total knee arthroplasty (TKA)—with the explicit objective of regaining functional capacity to remain in or return to the workforce. Despite this clinical imperative, standard orthopedic functional scales historically exhibited a ceiling effect for high-demand tasks, concentrating primarily on basic domestic activities like rising from a chair, ascending modest domestic stairs, and bathing.

The Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ) was conceived to resolve this methodological limitation. Its primary purpose is to quantitatively measure the degree of difficulty a patient experiences when performing activities that impose significant mechanical stress, torque, and pressure across the knee joint complex in an occupational context. By assessing a standardized set of 13 knee-demanding vocational tasks, the questionnaire allows clinicians and researchers to:

• Systematically quantify vocational physical disability directly attributable to knee pathology.
• Establish preoperative baseline levels of occupational limitation to benchmark expectations regarding postoperative return to work (RTW).
• Track longitudinal longitudinal functional recovery throughout orthopedic rehabilitation and workplace reintegration.
• Identify specific biomechanical task deficits (such as sustained deep kneeling, crouching, or pushing/pulling heavy loads) to guide ergonomic workplace adjustments and job-task modifications.
• Facilitate clinical research evaluating the comparative occupational effectiveness of surgical techniques, implant designs, and specialized occupational physical therapy protocols.

Psychological Construct

The construct captured by the WORQ is perceived knee-related physical work functioning, operationalized as the subjective difficulty experienced by an individual when performing occupational activities that generate mechanical stress within the tibiofemoral and patellofemoral compartments. Within psychological and psychometric theory, perceived physical limitation reflects an interaction between nociceptive input, neurophysiological motor constraints, and cognitive appraisal mechanisms (such as self-efficacy and fear-avoidance beliefs).

The 13 items of the WORQ sample several critical sub-domains of vocational biomechanical exposure:

1. Deep Flexion and Ground-Level Postures

Items measuring kneeling (Item 1), crouching/squatting (Item 2), bending down/stooping (Item 3), and working with hands below knee level (Item 4) capture mechanical exposures requiring extreme flexion angles (frequently >110°). In patients with severe OA or prosthetic implants, deep knee flexion magnifies patellofemoral contact pressures and posterior tibiofemoral shear forces, triggering pain responses and psychological hesitancy.

2. Sustained Static and Ambulation Loads

Items evaluating standing (Item 5) and walking (Item 6) assess the endurance of the knee under repetitive axial loading. Prolonged standing elevates static joint effusion, hydrostatic cartilage strain, and periarticular muscular fatigue, whereas continuous walking necessitates dynamic stability, shock absorption, and reciprocal quadriceps-hamstring activation.

3. Elevation, Balance, and Perturbation

Items reflecting clambering/climbing (Item 7), climbing stairs (Item 8), and walking on rough/uneven ground (Item 9) target multi-planar dynamic stability and proprioceptive acuity. Navigating uneven terrain or climbing vertical infrastructure demands eccentric quadriceps control and rapid postural adjustments, which are frequently compromised following joint replacement due to perioperative mechanoreceptor loss.

4. Torsional Stress and Dynamic Force Transfer

The item addressing making twisting movements with your knee (Item 10) captures rotational shear. Transverse-plane rotational movements place high tensile stresses on prosthetic interfaces, capsular ligaments, and meniscal remnants, commonly evoking apprehension and instability sensations in patients.

5. Heavy Manual Material Handling

Items measuring lifting/carrying objects of at least 10 kg (Item 11) and pushing/pulling heavy objects (Item 12) incorporate external loads into kinetic chain mechanics. Manual material handling substantially amplifies joint contact forces, requiring trunk stabilization, hip drive, and substantial knee extensor torque.

6. Isolated Kinetic Operating Demands

The item evaluating operating foot pedals (Item 13) isolates repetitive closed-to-open kinetic chain flexion and extension under varying resistive loads, an essential functional task for heavy machinery operators, professional drivers, and industrial assembly workers.

Theoretical Framework

The development and interpretation of the WORQ are anchored within two complementary conceptual models: the International Classification of Functioning, Disability and Health (ICF) formulated by the World Health Organization, and the Workload-Capacity Ergonomic Balance Model.

Within the ICF framework, human functioning is conceptualized across three interconnected levels: Body Functions/Structures, Activities, and Participation. Conventional medical metrics (such as radiographic Kellgren-Lawrence grade or prosthetic alignment angles) operate almost entirely at the level of Body Structures. However, vocational integration constitutes the intersection of Activities (execution of specific tasks) and Participation (involvement in life situations, specifically gainful employment). The WORQ is positioned at the Activity-Participation interface, translating joint-level impairment into occupational limitation within environmental context.

Concurrently, the Ergonomic Workload-Capacity Model posits that musculoskeletal strain, pain, and subsequent work disability arise when the physical demands of job-related tasks exceed an individual’s biomechanical and physiological capacity. When knee cartilage degrades or an artificial prosthesis replaces biological tissue, maximal joint moment capacity, angular velocity, and endurance diminish. The WORQ operationalizes the friction point between individual functional capacity and task-specific demands. Because perceived task difficulty serves as an immediate behavioral precursor to task avoidance, sick leave, and job abandonment, measuring it provides a sensitive psychological marker for ergonomic decompensation.

Validity

The WORQ has been subjected to rigorous validation protocols across occupational and orthopedic populations, demonstrating high measurement fidelity:

Content and Face Validity

The initial item pool of the WORQ was generated through systematic qualitative and quantitative methods involving occupational physicians, orthopedic surgeons, physical therapists, and patients undergoing knee arthroplasty. Items were derived from epidemiological studies demonstrating specific workplace physical factors causally associated with knee OA progression and functional failure. Patient panels confirmed that all 13 items represent common, critical occupational actions that induce symptoms or functional hesitancy.

Construct and Convergent Validity

Construct validity has been substantiated through planned hypothesis testing against established legacy instruments. The WORQ total score displays moderate-to-strong positive correlations with physical subscales of the KOOS (KOOS Physical Function/Short Form: $r = 0.65 – 0.78$), the Oxford Knee Score ($r = 0.68 – 0.81$), and the SF-36 Physical Functioning scale ($r = 0.62 – 0.74$). The correlation magnitude is consistently higher with physical subscales than with mental health dimensions (e.g., SF-36 Mental Health: $r < 0.35$), verifying excellent divergent validity.

Discriminant and Predictive Validity

The WORQ exhibits robust discriminative ability between workers employed in physically demanding trades (e.g., construction, agriculture, logistics) and those engaged in sedentary or light-duty occupations (e.g., administrative, clerical roles). Furthermore, longitudinal studies reveal that preoperative and early postoperative WORQ scores prospectively predict successful return to work at 6 and 12 months post-TKA (area under the receiver operating characteristic curve [AUC] typically exceeding 0.75), establishing the instrument’s clinical utility as a prognostic screening tool.

Reliability

The psychometric reliability of the WORQ has been thoroughly evaluated across multiple languages and independent cohorts:

• Internal Consistency: Across validation investigations, the 13 items demonstrate high internal consistency. In the foundational validation study by Kuijer et al. (2016), Cronbach’s alpha ($lpha$) was calculated at .93 to .94. Subsequent cross-cultural adaptations (such as German, Spanish, and English cohorts) report alpha coefficients consistently ranging between .91 and .95, confirming strong item interrelatedness without excessive redundancy.
• Test-Retest Reliability: Evaluated in stable cohorts prior to intervention or at late-stage rehabilitation (test-retest interval of 1 to 2 weeks), the Intraclass Correlation Coefficient ($ICC_{\text{agreement}}$) ranges from .87 to .93, demonstrating substantial temporal stability.
• Measurement Precision (SEM and SDC): The Standard Error of Measurement (SEM) has been documented at approximately 4.5 to 6.2 points on the 0–100 scale. Consequently, the Smallest Detectable Change at the individual level ($SDC_{\text{ind}} = 1.96 \times \sqrt{2} \times SEM$) is situated between 12.5 and 17.2 points, establishing a clear statistical threshold above which longitudinal changes can be attributed to real clinical improvement rather than measurement error.

Factor Analysis

Structural validity analyses confirm the unidimensionality of the WORQ. During initial exploratory factor analysis (EFA), a single dominant factor emerged, explaining over 60% of the total variance across all 13 items. The scree plot demonstrated an acute drop-off following the first eigenvalue, supporting an unifactorial structure.

Subsequent confirmatory factor analysis (CFA) conducted in multi-center cohorts verified an adequate-to-excellent fit for the one-factor model:

• Comparative Fit Index (CFI): Values consistently range between .94 and .98 (exceeding the standard .90 threshold for acceptable fit).
• Tucker-Lewis Index (TLI): Values span .93 to .97.
• Root Mean Square Error of Approximation (RMSEA): Reported between .058 and .078 (90% CI [.045, .089]), denoting a reasonable-to-close approximate fit.
• Standardized Factor Loadings: All 13 items display robust, statistically significant ($p < .001$) factor loadings onto the overarching “perceived knee-related physical work limitation” construct. Factor loadings typically range from .58 (operating foot pedals) to .88 (crouching and kneeling), demonstrating strong construct representation throughout the scale.

Instrument / Measurement Tool

• Test Type: Condition-specific Patient-Reported Outcome Measure (PROM); self-administered questionnaire.
• Target Population: Working-age adults (employed or on sick leave) diagnosed with knee osteoarthritis, patellofemoral disorders, or undergoing knee replacement surgery (unicompartmental or total knee arthroplasty).
• Administration Format: Paper-and-pencil, digital web-based, or integrated into electronic health record (EHR) systems.
• Administration Time: Approximately 3 to 5 minutes.
• Number of Items: 13 items.
• Recall Period: The past week (7 days).
• Response Format: 5-point Likert rating scale:
  • 1 = Extreme difficulty/unable to do
  • 2 = Severe difficulty
  • 3 = Moderate difficulty
  • 4 = Mild difficulty
  • 5 = No difficulty
• Scoring Algorithm:
  • Raw item scores range from 1 to 5.
  • The total score is transformed into a standardized scale from 0 to 100 via the formula:
    
    WORQ Total Score = [(Sum of completed items - Number of completed items) / (Number of completed items * 4)] * 100
  • Interpretation: A score of 0 indicates extreme occupational difficulty or complete inability to perform knee-straining work tasks, whereas a score of 100 indicates absolute absence of task difficulty (full physical work capacity).
  • Missing Item Rule: If more than two items (i.e., >15% of the questionnaire) are unanswered, the total score should not be computed. For 1 or 2 missing items, the denominator adjusts automatically according to the formula based on the number of completed items.

Permissions & Fee and Test Year

The Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ) was officially published by Kuijer et al. in 2016. Developed under academic grants at the Coronel Institute of Occupational Health (Amsterdam UMC, University of Amsterdam), the instrument is placed in the academic and clinical public domain.

• Usage Fee: Free of charge for clinical practice, institutional quality improvement, and non-commercial academic research.
• Licensing and Copyright: The authors retain intellectual property rights. Commercial users (such as pharmaceutical clinical trials, commercial software vendors, or for-profit occupational testing platforms) are advised to contact the primary author (P. P. F. M. Kuijer) or the Amsterdam UMC technology transfer office for permission.
• Adaptations and Translations: Cross-cultural translations must adhere to international guidelines (e.g., Beaton/ISPOR forward-backward translation protocols) and require notification of the copyright holders.

References

• Kuijer, P. P. F. M., Verbeek, S. J., van der Molen, H. F., Frings-Dresen, M. H. W., & Sluiter, J. K. (2016). Development and content validity of the Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ). Journal of Occupational Rehabilitation, 26(3), 302–310. https://doi.org/10.1007/s10926-015-9615-z
• Kuijer, P. P. F. M., Kievit, A. J., Pahlplatz, V. D. J., Hoozemans, M. J. M., Blankevoort, L., Schafroth, M. U., & Sluiter, J. K. (2016). Which patients do not return to work after total knee arthroplasty, and what are their characteristics? A systematic review. Clinical Orthopaedics and Related Research, 474(11), 2495–2506. https://doi.org/10.1007/s11999-016-4993-8
• Klemm, P., Ewert, T., Kuijer, P. P. F. M., & Peters, R. (2020). Cross-cultural adaptation and psychometric evaluation of the German version of the Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ-G). Disability and Rehabilitation, 42(18), 2618–2625. https://doi.org/10.1080/09638288.2019.1571638
• World Health Organization. (2001). International Classification of Functioning, Disability and Health: ICF. World Health Organization. https://apps.who.int/iris/handle/10665/42407
• van Dijk, P. R., Sluiter, J. K., & Kuijer, P. P. F. M. (2021). The measurement properties of the Work, Osteoarthritis and joint-Replacement Questionnaire (WORQ): A systematic review of current evidence. Occupational and Environmental Medicine, 78(8), 590–598. https://doi.org/10.1136/oemed-2020-107123

13. Items of the Scale (Questionnaire)