Valid and reliable instruments are required in order to determine effective interventions in the treatment of musculoskeletal disorders (MSD). Today, there is a lack of consistency in use of self-report outcome measures in research and practice, which makes it difficult or impossible to compare treatment effects. The questionnaires differ widely, in content as well as quality. The focus of present study was on assessment of physical functioning among people with MSD in the neck. The aim was to investigate how physical function is assessed in people with MSD in the neck. Specifically we wanted to determine: - Which questionnaires are used to assess physical function in people with musculoskeletal disorders in the neck? - What do those questionnaires measure? - What are the measurement properties of the questionnaires?

The study was performed as a systematic literature review in order to identify articles presenting the questionnaires and psychometric tests of them. Items included in the questionnaires were classified according to the "International Classification of Functioning, Disability and Health", ICF. Thereafter, all psychometric tests of the different questionnaires were analysed with respect to relevant quality indicators using the "Cosmin checklist".

Included in the final analysis were 10 questionnaires and 32 articles presenting psychometric tests of them. The analysis revealed that questionnaires for measuring physical functioning in neck disorders differ substantially in items and extent to which their psychometric properties have been evaluated. Most questionnaires contained only the ICF-components body functions and activity and participation, more often activity and participation. The most psychometrically tested questionnaire was Neck Disability Index. Remaining questionnaires were tested in fewer studies and only some of the properties in the Cosmin checklist were tested for most of them.

Questionnaires for assessment of physical function in people with neck disorders tend to focus more on the ability to engage in activities of daily life than on physical function as such. Furthermore, the measurement properties of the questionnaires have usually been evaluated in few studies. It is vital to measure aspects that are of importance for the individual wellbeing and ability to function in work and daily life when evaluating neck disorders. However, to increase the validity of the results in clinical and research studies, it is also important to include the most relevant aspects of physical function. We recommend more psychometric testing of the questionnaires, especially those that cover important aspects of the ICF categories. To ensure coverage of important aspects, validation of the questionnaires against patients and practitioners is needed.

A review and analysis of this kind makes it easier for researchers and clinicians to select the most suitable questionnaire for their own purpose, based on the content and quality of the questionnaire.