Western Ontario Shoulder Instability Index (WOSI)

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Western Ontario Shoulder Instability Index (WOSI)

It is thought that instability of the shoulder joint leads to special problems of assessment that traditional shoulder patient-reported outcome measures (PROMs) may fail to capture. Instability of the shoulder has symptoms that are often intermittent and characterized less by pain than by the anticipation of problems arising in association with certain activities [1].

Developed in 1988, specifically for use in shoulder instability, the Western Ontario Shoulder Instability Index (WOSI) is a validated PRO measure. It’s proven to be a useful outcome measure in several clinical studies and has been translated and validated in Italian, German, Swedish, and Japanese [2].

The WOSI questionnaire consists of 21 items, each scored on a 100mm Visual Analogue Scale (VAS). Each item falls into one of the domains of physical function, sports/recreation/work, lifestyle, and emotional well-being. Each question is scored between 0-100 points and the summation of all the questions results in a final WOSI score. The final score ranges from 0 (best possible score – the patient is experiencing no decrease in shoulder-related quality of life) to 2100 (worst score – signifies extreme distress in shoulder-related quality of life).

The WOSI is a valid, reliable, and sensitive assessment for patients with shoulder problems that are associated with instability and it’s widely recommended for use in the evaluation of these patients.


The Western Ontario Shoulder Instability Index is a patient-friendly survey and has excellent test-retest reliability. It’s also designed for clinical trials and is valid for comparing, and even aggregating cohort studies [1].

Additionally, studies have found WOSI to be more responsive (sensitive to change) than other measures for shoulder instability including DASH, Constant, ASES and UCLA Shoulder Score [3].


The WOSI takes about 10 minutes for patients to complete which compares unfavorably to other outcome measures that take a considerably shorter amount of time (2-5 minutes). There’s also comparatively little validity and responsiveness information for the WOSI and its 0-2100 scale is not comparable to other outcome measures (although it may be converted to a 0-100 point scale).

There is much consensus amongst clinicians that the Western Ontario Shoulder Instability Index is the preferred PROM when evaluating treatments of shoulder instability. It’s easy to administer and has good reliability and responsiveness [1, 2].


No license is required for use of the Western Ontario Shoulder Instability Index.


  1. Björn Salomonsson, Susanne Ahlström, Nils Dalén & Ulf Lillkrona (2009) The Western Ontario Shoulder Instability Index (WOSI): validity, reliability, and responsiveness retested with a Swedish translation, Acta Orthopaedica, 80:2, 233-238, DOI:10.3109/17453670902930057 http://www.tandfonline.com/doi/pdf/10.3109/17453670902930057
  2. Van der Linde, J. A., Willems, W. J., van Kampen, D. A., van Beers, L. W., van Deurzen, D. F., & Terwee, C. B. (2014). Measurement properties of the Western Ontario Shoulder Instability Index in Dutch patients with shoulder instability. BMC musculoskeletal disorders, 15(1), 1. http://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/1471-2474-15-211
  3. Kirkley, A., Griffin, S., McLintock, H., & Ng, L. (1998). The Development and Evaluation of a Disease-Specific Quality of Life Measurement Tool for Shoulder Instability The Western Ontario Shoulder Instability Index (WOSI). The American Journal of Sports Medicine, 26(6), 764-772. http://www.ncbi.nlm.nih.gov/pubmed/9850776

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