WOMAC index or Western Ontario and McMaster Universities Osteoarthritic Index is used to assess the course of disease or response to treatment in patients with knee or hip osteoarthritis.
Initially developed in 1982, the WOMAC has undergone multiple revisions.
What Does WOMAC Measure?
WOMAC measures of three subscales on a scale of 0-4. [None – 0, Mild – 1, Moderate – 2, Severe – 3, Extreme – 4] It measures a total of 24 items and offers 5 responses for each item measured. Recall period for items is 48 hours. Three subscales are
- Pain severity during various positions or movements – 5 items
- The severity of joint stiffness – 2 items
- Difficulty performing daily functional activities – 17 items
Validity of WOMAC
Studies have generally reported adequate internal consistency for the pain subscale, although there have been reports slightly lower than adequate. WOMAC can be considered to have face and content validity. It also appears s to be responsive to change following surgical and nonsurgical interventions for knee OA and chondral defects.
WOMAC consists of a questionnaire which is aimed to assess three items – pain, joint stiffness and difficulty in physical activity.
In this subscale the questions are asked about pain felt in different situations namely walking, stair climbing, night pain, pain at rest and pain at weight bearing.
Responses are to be provided on a scale that is from 0-4 [the scale has been described previously in the article]
This measure joint stiffness in the morning and rest of the day. This subscale has just two questions.
This is the largest subscale and consists of 17 questions that assess physical function in the following conditions.
- Descending stairs
- Ascending stairs
- Rising from sitting
- Bending to floor
- Walking on flat surface
- Getting in/out of car
- Going shopping
- Putting on socks
- Lying in bed
- Taking off socks
- Rising from bed
- Getting in/out of the bath
- Getting on/off toilet
- Heavy Domestic duties
- Light domestic duties
A total of 24 items are asked thus making a possible maximum score of 96.
The final score is expressed in percentage and calculated by dividing an individual’s score by total score and multiplying that by 100.
Interpretation of WOMAC Score
Higher scores on the WOMAC indicate worse pain, stiffness, and functional limitations.