WOMAC Index Calculator
Osteoarthritis Pain, Stiffness & Function (WOMAC)
Pain
5 questions
Stiffness
2 questions
Physical Function
17 questions
Score Summary
Pain0
Stiffness0
Physical Function0
Total Score0
Max Possible96
Guidelines & Evidence
Verified
Last Review: 2026-07-17
When to Use
When to Use
Assessment of symptoms in patients with hip or knee osteoarthritis (OA)
Pre-treatment and post-treatment outcome measurement in OA management
Clinical trials evaluating OA interventions: pharmacologic, surgical, physical therapy
Long-term monitoring of OA progression and treatment effectiveness
Joint replacement outcomes assessment (hip and knee arthroplasty)
Comparative effectiveness research across OA treatment modalities
Patient Population
Designed for adults with hip or knee osteoarthritis. The most widely used disease-specific outcome measure for OA clinical trials worldwide. Validated across diverse populations and treatment settings.
How it Works
Formula
Total Score = Pain (0-20) + Stiffness (0-8) + Physical Function (0-68) = 0 to 96
Pain (5 items): Walking, stairs, nocturnal, sitting/lying, standing — each scored 0-4
Stiffness (2 items): Morning stiffness, stiffness after sitting — each scored 0-4
Function (17 items): Daily activities from descending stairs to light domestic duties — each scored 0-4
Higher scores indicate worse symptoms and greater functional limitation
Response Options
| Score | Level | Description |
|---|---|---|
| 0 | None | No pain/stiffness/difficulty |
| 1 | Mild | Slight symptoms, no activity limitation |
| 2 | Moderate | Noticeable symptoms, some limitation |
| 3 | Severe | Significant symptoms, marked limitation |
| 4 | Extreme | Incapacitating symptoms |
Clinical Pearls
Interpretation Guide
| Total Score | Severity | Clinical Implication |
|---|---|---|
| 0 – 24 | Mild | Minimal OA impact; lifestyle modifications sufficient |
| 25 – 48 | Moderate | Symptoms affecting daily life; consider treatment |
| 49 – 72 | Severe | Significant limitation; pharmacologic therapy indicated |
| 73 – 96 | Extreme | Crippling symptoms; surgical consultation warranted |
Key Considerations
WOMAC is the gold standard outcome measure for OA clinical trials per FDA/EMA guidelines
The Likert scale version (0-4) is most commonly used; a VAS version also exists
Subscale scores should be reported alongside total score for comprehensive assessment
MCID varies by domain: Pain 2-3 points, Function 3-5 points, Stiffness 1-2 points
The WOMAC has strong correlation with the SF-36 physical function domain
Common Pitfalls
Ensure consistent administration mode (self-report vs. interview) across visits
The VAS version (0-100mm) and Likert version (0-4) are NOT interchangeable
Missing data: at least 50% of items per subscale must be completed
Do not use WOMAC for inflammatory arthritis (RA, psoriatic) — designed for OA specifically
Next Steps
Clinical Actions
01
Calculate total and subscale scores; compare to pre-treatment baseline
02
For mild OA: recommend lifestyle modification, exercise, weight management
03
For moderate OA: initiate pharmacotherapy (acetaminophen, NSAIDs, topical agents)
04
For severe OA: consider intra-articular corticosteroids or hyaluronic acid
05
For extreme OA: refer for joint replacement surgical consultation
06
Re-administer WOMAC at each follow-up to track treatment response objectively
The Evidence
Primary Reference
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
Bellamy N et al. • Journal of Rheumatology. 1988;15(12):1833-1840 — Original validation of the WOMAC Index
Psychometric Properties
Test-retest reliability: ICC 0.85-0.95 across all domains
Internal consistency: Cronbach's alpha 0.85-0.95
MCID: Pain 2-3 points, Function 3-5 points, Stiffness 1-2 points
Responsiveness: Large effect sizes for joint replacement (Cohen's d > 2.0)
Used as primary endpoint in over 1,000 clinical trials
Origins & History
Historical Background
The WOMAC Index was developed by Dr. Nicholas Bellamy and colleagues at the University of Western Ontario, London, Canada. The name stands for Western Ontario and McMaster Universities Osteoarthritis Index. First published in 1988, it has become the most widely used disease-specific outcome measure for hip and knee osteoarthritis in clinical trials worldwide.
Last Comprehensive Review: 2026-07-17