WOMAC Osteoarthritis Index
Also known as: WOMAC Scale, WOMAC Arthritis Index
The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is a widely used patient-reported outcome measure designed to assess pain, stiffness, and physical function in patients with osteoarthritis of the hip or knee. Developed by Bellamy and colleagues in 1988, it has become the gold standard outcome measure in osteoarthritis clinical trials and practice.
Key highlights
- Gold standard outcome measure in osteoarthritis research and clinical practice with decades of validation.
- Highly responsive to clinical change and treatment effects; capable of detecting meaningful improvement with therapy or surgery.
- Multidimensional assessment of pain, stiffness, and function captures the full impact of osteoarthritis.
- Available in 70+ languages and adapted for diverse cultural contexts; free to use in research and clinical settings.
Intuition
This section is available to Pro members. Upgrade to Pro
How it works
This section is available to Pro members. Upgrade to Pro
When to use it
WOMAC is the primary measure for patients with hip or knee osteoarthritis in clinical practice and research settings. Use it at baseline to establish disease severity, during follow-up to monitor progression, and post-intervention to quantify treatment response. It is valuable in orthopedic rehabilitation, rheumatology, primary care, and clinical trials. Avoid in non-arthritic populations or when measuring function in other joint diseases.
Strengths & limitations
- Gold standard outcome measure in osteoarthritis research and clinical practice with decades of validation.
- Highly responsive to clinical change and treatment effects; capable of detecting meaningful improvement with therapy or surgery.
- Multidimensional assessment of pain, stiffness, and function captures the full impact of osteoarthritis.
- Available in 70+ languages and adapted for diverse cultural contexts; free to use in research and clinical settings.
- Designed specifically for hip or knee osteoarthritis; not applicable to other joint diseases or localized conditions.
- Relies on patient self-report; subject to recall bias and social desirability bias in responses.
- Does not assess systemic features of osteoarthritis (e.g., radiographic severity, inflammation markers) or comorbidities that may affect function.
Common pitfalls
This section is available to Pro members. Upgrade to Pro
Applications
This section is available to Pro members. Upgrade to Pro
Frequently asked
What is the difference between the WOMAC Likert and VAS versions?
The WOMAC Likert version uses a 5-point ordinal scale (0–4) for each item, while the VAS version uses a 100-mm visual analog scale. Both yield comparable results, but the Likert version is simpler for patients and clinicians to use. Use the same format longitudinally to ensure comparability.
Can WOMAC be used in patients with both hip and knee arthritis?
The standard WOMAC is designed for single-joint assessment (either hip or knee). If both joints are significantly affected, administer WOMAC separately for each joint or consider generic outcome measures; do not combine the scores.
What is a clinically meaningful change in WOMAC scores?
A change of 8–12 points (or 15–20% improvement) on the total WOMAC score is generally considered clinically meaningful. For pain subscale, 4–6 points; for function subscale, 6–10 points. These thresholds should be interpreted alongside patient-reported global improvement.
How long should I wait between WOMAC administrations to detect real change?
Minimum 4–6 weeks is recommended to allow time for therapeutic interventions to take effect and minimize measurement error. More frequent assessments (weekly) are prone to noise and do not reflect true clinical change.
Sources
- 1.Bellamy, N., Buchanan, W. W., Goldsmith, C. H., Campbell, J., & Stitt, L. W. (1988). Validation study of WOMAC: a health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. Journal of Rheumatology, 15(12), 1833–1840.
- 2.Bellamy, N. (1997). WOMAC: a 20-year experiential review of a patient-centered self-reported health status questionnaire. Journal of Rheumatology, 29(12), 2473–2476.
You have read it. What now?
Cite this page
ScholarGate. (2026, June 3). WOMAC Osteoarthritis Index. ScholarGate. https://scholargate.app/rehabilitation/womac