A popular patient-reported outcome (PRO) tool used for evaluation with hip and knee osteoarthritis is the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC).
WOMAC has been used extensively in research studies, undergone rigorous psychometric validation, and is frequently utilized in many clinical trials. Additionally, WOMAC has been recognized by the Outcome Measures in Rheumatoid Arthritis Clinical Trials group (OMERACT) and Osteoarthritis Research Society International (OARSI), alongside many other regulatory bodies and agencies.
WOMAC also has the additional advantage of being validated for use in multiple formats. It can be administered in person, via computer, by telephone interview, and can even be delivered to mobile devices (m-WOMAC) . Additionally, a reduced seven-point WOMAC scale has also been validated.
Developed over 20 years ago, WOMAC has been revised multiple times to its most current version, 3.1. The current WOMAC survey is comprised of 24 items divided into three subscales: Pain (5 items), stiffness (2 items), and physical function (17 items). Patients are asked a range of questions about their ability to carry out daily activities such as using the stairs, rising from sitting, lying in bed and conducting light or heavy domestic duties. All the items are scored on a scale of 0-4 (lower scores indicate lower levels of symptoms or physical disability). Values are summed up for a combined WOMAC score. This is also the most popular and common method used, although other aggregation methods have been used. The higher the score, the higher the amount of pain, stiffness, and a high level of functional limitations.
The relatively simple nature of the WOMAC survey means that it can be completed in a short amount of time and scored in just 5-10 minutes.
The WOMAC is an exceedingly popular tool, highlighted by its extensive use in both observational and epidemiological studies , as well as its availability in over 65 languages .
The questionnaire can also be used for a variety of different conditions. Originally WOMAC was developed for use amongst patients with knee and/or hip osteoarthritis, but i’s also been used for patients with low back pain, rheumatoid arthritis, juvenile rheumatoid arthritis, systemic lupus erythematosus and fibromyalgia .
A potential weakness of the WOMAC is the stiffness subscale (one of the three scoring subscales). It’s shown to have low test-retest reliability, and the physical function subscale is limited in its ability to detect change.
WOMAC appears to have very few significant weaknesses and has excellent usability. It’s relatively short when compared to other PRO tools. Its popularity, availability in multiple formats, and easy scoring methodology make it a great choice for the evaluation of patients with hip and knee osteoarthritis.
A license is required to use the WOMAC tool. Licensing information, research requests, and permission to use WOMAC can be submitted to womac.org.
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- Wolfe F, Kong SX. Rasch analysis of the Western Ontario MacMaster questionnaire (WOMAC) in 2205 patients with osteoarthritis, rheumatoid arthritis, and fibromyalgia. Ann Rheum Dis. 1999; 58(9):563-568.
- http://www.ncbi.nlm.nih.gov/pubmed/20609562 – Osteoarthritis Index delivered by mobile phone (m-WOMAC) is valid, reliable, and responsive
- (3-C) Patt JC, Mauerhan DR. Outcomes research in total joint replacement: a critical review and commentary. Am J Orthop (Belle Mead NJ) 2005;34-4:167-72.