WOMAC Score: How to Measure Osteoarthritis Pain, Stiffness, and Physical Function

Osteoarthritis symptoms can affect far more than joint comfort. Pain while walking, difficulty using stairs, morning stiffness, and trouble completing household activities can all influence a person’s independence and quality of life. Because these experiences cannot be fully represented by imaging or a physical examination, patient-reported outcome measures provide another way to document how osteoarthritis affects daily living.

The WOMAC score is one of the most widely used patient-reported measures for hip and knee osteoarthritis. It asks patients to rate their pain, stiffness, and physical function, creating a repeatable record that can be tracked before and after treatment. The measure may be used during conservative care, surgical planning, postoperative follow-up, quality-improvement programs, and clinical research.

This article explains what the WOMAC score measures, how scoring works, what higher and lower scores mean, and how to interpret changes over time.

What Is the WOMAC Score?

WOMAC stands for the Western Ontario and McMaster Universities Osteoarthritis Index. The instrument was developed to measure outcomes that matter to people with osteoarthritis of the hip or knee and was formally validated in a study published in 1988.¹

The questionnaire contains 24 items divided into three subscales:

• Pain: 5 items

• Stiffness: 2 items

• Physical function: 17 items

Patients answer questions based on the difficulty or symptoms they experience during common activities. Depending on the version being used, responses may refer to experiences during the past 48 hours.²

The WOMAC pain section asks about pain during activities such as walking, using stairs, sitting or lying down, standing, and being in bed. The stiffness section addresses stiffness after first waking and later in the day. The physical function section covers activities such as rising from a chair, bending, shopping, getting in and out of a car, putting on socks, and performing household tasks.

Together, these sections provide a broader picture than a single pain rating. Two patients may report similar pain intensity while experiencing very different levels of stiffness or activity limitation. Reviewing each subscale separately can show where the greatest burden lies.

The WOMAC is a disease-specific measure. It was designed for hip and knee osteoarthritis rather than as a general assessment for every musculoskeletal condition. Its findings should therefore be interpreted within the patient’s diagnosis, treatment plan, and functional goals.

How Is the WOMAC Score Calculated?

Several versions of the WOMAC questionnaire exist, including Likert, visual analog, and numerical rating formats.³ Because the response scales differ, the possible score ranges can differ as well.

A commonly used Likert version asks the patient to rate each item using five response choices:

• 0: None

• 1: Mild

• 2: Moderate

• 3: Severe

• 4: Extreme

With this method, the raw score ranges are:

WOMAC subscale	Number of items	Possible score
Pain	5	0–20
Stiffness	2	0–8
Physical function	17	0–68
Total score	24	0–96

The score for each subscale is calculated by adding the responses within that section. A total WOMAC score may then be calculated by adding the three subscale scores.

For example, a patient with a pain score of 12, stiffness score of 4, and physical function score of 38 would have a total raw score of:

12 + 4 + 38 = 54

In this scoring direction, higher scores represent greater pain, stiffness, and physical difficulty. Lower scores represent fewer symptoms and less difficulty.

Some organizations convert raw scores to a 0-to-100 scale. A common normalization formula is:

Normalized score = raw score ÷ maximum possible score × 100

Using the previous example:

54 ÷ 96 × 100 = 56.25

The normalized total would be approximately 56 out of 100, with a higher number indicating worse symptoms.

Scoring direction must always be confirmed. Some studies and electronic systems reverse the scale so that 100 represents better joint health. Published research has found inconsistent reporting of WOMAC versions, scoring ranges, and score direction, which can make comparisons difficult.⁴ Reports should state the questionnaire version, response format, score range, and meaning of higher scores.

A documentation note might read:

WOMAC Likert version, raw total score 54/96. Higher scores indicate greater symptom burden and functional difficulty.

This added context reduces ambiguity when results are reviewed by another department, compared across facilities, or exported for analysis.

What Does a WOMAC Score Mean?

A WOMAC score does not diagnose osteoarthritis or determine treatment on its own. It describes the patient’s reported symptoms and functional limitations at a particular point in time.

A high pain score may indicate that activities such as walking, stair use, or weight bearing are producing substantial discomfort. A high stiffness score may reflect prolonged difficulty after waking or following periods of rest. A high physical function score can point to limitations across mobility, self-care, transportation, and household activities.

The separate subscale results often provide more useful information than the total alone. Consider these two patients:

• Patient A has high pain and moderate functional difficulty.

• Patient B has moderate pain and high functional difficulty.

Their total scores could be similar, but their treatment priorities and support needs may differ. Patient A may require greater attention to symptom management, while Patient B may need more support with mobility, strength, activity modification, or environmental barriers.

The WOMAC score should be reviewed alongside other information, including:

• Symptom duration and recent changes

• Physical examination findings

• Imaging findings when clinically indicated

• Walking tolerance and activity level

• Use of assistive devices

• Comorbid conditions

• Patient goals and treatment preferences

Research has shown that the WOMAC can detect changes in pain and physical function following treatment and rehabilitation.⁵ Still, a score change must be interpreted in context. A small numerical improvement may matter greatly to a patient if it allows them to climb stairs or return to a valued activity. A larger change may have less practical meaning if daily function remains restricted.

There is no single universal WOMAC cutoff that divides mild, moderate, and severe osteoarthritis for every patient population. Score distributions can vary by joint, treatment type, baseline status, questionnaire format, and calculation method. Using locally invented severity categories without validation may create misleading conclusions.

For routine tracking, the strongest comparison is often the patient’s current score against their own baseline score, using the same version and scoring method each time.

How Much Change in a WOMAC Score Is Meaningful?

A lower WOMAC score generally reflects improvement when higher values indicate worse symptoms. For example, a total score that decreases from 54 to 36 represents an 18-point raw improvement on a 0-to-96 scale.

The percentage change from baseline can be calculated as:

Change ÷ baseline score × 100

For a decrease from 54 to 36:

18 ÷ 54 × 100 = 33.3% improvement

Percentage change can make results easier to compare, but it does not automatically establish that the improvement is meaningful to the patient.

Terms such as minimal clinically important difference, minimal important change, and meaningful within-patient change describe attempts to identify how much score movement reflects a noticeable or valuable change. Studies have reported different WOMAC thresholds across treatments and populations. A systematic review found substantial variation in estimates for WOMAC pain and function, influenced by study methods and patient characteristics.⁶

Another systematic review examining knee osteoarthritis outcome measures after nonsurgical care reported that minimal important change estimates varied to calculation method, outcome domain, and clinical setting.⁷ This means a single number should not be applied to every use of the WOMAC.

When interpreting change, consider:

1. The version and scale used: A 10-point change has a different meaning on a 0-to-96 scale than on a 0-to-100 scale.

2. The starting score: Patients with low baseline scores have less room for numerical improvement.

3. The treatment setting: Expected changes may differ after joint replacement, exercise-based care, medication, or injections.

4. The subscale involved: Improvement in pain may occur at a different rate than improvement in physical function.

5. The patient’s own report: Ask if the person feels better, worse, or unchanged, and which activities have become easier.

For organizational reporting, the selected interpretation threshold should be documented in advance and linked to evidence from a similar patient population and treatment setting.

WOMAC Score Example

Consider a patient with knee osteoarthritis who completes the Likert version of the WOMAC before starting a structured treatment plan.

Baseline assessment

• Pain: 14/20

• Stiffness: 5/8

• Physical function: 45/68

• Raw Score Total: 64/96

Normalized total:

64 ÷ 96 × 100 = 66.7

Eight weeks later, the patient completes the same version under similar conditions.

Follow-up assessment

• Pain: 9/20

• Stiffness: 3/8

• Physical function: 31/68

• Raw Score Total: 43/96

Normalized total:

43 ÷ 96 × 100 = 44.8

The raw total decreased by 21 points, and the normalized score decreased by 21.9 points. The patient also reports being able to walk farther, use stairs with less discomfort, and complete meal preparation without needing to sit down.

This example shows why combining the score with activity-based details matters. The WOMAC documents numerical change, while the patient’s description shows how that change appears in daily life.

Using the WOMAC Score Consistently

Consistent administration is necessary for meaningful comparison. Changing the questionnaire format, recall period, language version, scoring direction, or collection method can introduce variation unrelated to the patient’s health.

A standardized workflow should specify:

• The approved WOMAC version

• The response scale being used

• The recall period

• How missing responses are handled

• Raw or normalized scoring

• The direction of the scale

• Assessment timing

• Where scores are stored

• How results are shared with the care team

Digital collection can reduce manual calculation and make longitudinal results easier to review. Electronic systems may display pain, stiffness, function, and total scores as separate trends, helping teams identify improvement, decline, or a plateau between visits.

The WOMAC is a registered instrument, and access or licensing requirements may apply depending on the intended use, format, language, and distribution method. Organizations should confirm current permissions before reproducing the questionnaire or adding it to a digital platform.⁸

The WOMAC score offers a structured view of how hip or knee osteoarthritis affects pain, stiffness, and daily function. Its value comes from repeated use with a clearly identified version and scoring method. When paired with clinical findings, patient goals, and activity-based observations, it can support treatment discussions, progress monitoring, and outcome reporting across an episode of care.

References

1. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. 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. 1988;15(12):1833–1840.
   https://pubmed.ncbi.nlm.nih.gov/3068365/

2. American Physical Therapy Association. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
   https://www.apta.org/patient-care/evidence-based-practice-resources/test-measures/western-ontario-and-mcmaster-universities-osteoarthritis-index-womac

3. Bellamy N. WOMAC Osteoarthritis Index. WOMAC and AUSCAN Osteoarthritis Global Index.
   https://womac.com/womac/

4. Copsey B, Thompson JY, Vadher K, et al. Problems persist in reporting of methods and results for the WOMAC measure in hip and knee osteoarthritis trials. Quality of Life Research. 2019;28(2):335–343.
   https://pmc.ncbi.nlm.nih.gov/articles/PMC6373321/

5. Angst F, Aeschlimann A, Stucki G. Responsiveness of the WOMAC osteoarthritis index as compared with the SF-36 in patients with osteoarthritis of the legs undergoing a rehabilitation intervention. Annals of the Rheumatic Diseases. 2001;60(9):834–840.
   https://pmc.ncbi.nlm.nih.gov/articles/PMC1753825/

6. Devji T, Guyatt GH, Lytvyn L, et al. Application of minimal important differences in degenerative knee disease outcomes: A systematic review and case study to inform BMJ Rapid Recommendations. BMJ Open. 2017;7:e015587.
   https://pmc.ncbi.nlm.nih.gov/articles/PMC5777462/

7. Silva MDC, Perriman DM, Fearon AM, et al. Minimal important change and difference for knee osteoarthritis outcome measurement tools after nonsurgical interventions: A systematic review. BMJ Open. 2023;13:e063026.
   https://pubmed.ncbi.nlm.nih.gov/37202126/

8. Clement ND, Bardgett M, Weir D, Holland J, Gerrand C, Deehan DJ. What is the minimum clinically important difference for the WOMAC Index after total knee arthroplasty? Clinical Orthopaedics and Related Research. 2018;476(10):2005–2014.
   https://pubmed.ncbi.nlm.nih.gov/30179956/