The Neck Disability Index (NDI) is the most widely used self-report measure of neck-related disability. This page explains what the NDI is, what it measures, the items it contains, how it is scored, and how it is used.
What is the Neck Disability Index?
The Neck Disability Index (NDI) is a ten-item, self-reported questionnaire that measures neck-specific disability. It was developed by Vernon and Mior as a modification of the Oswestry Low Back Pain Disability Index and published in 1991, and it has become a standard instrument for measuring self-rated disability due to neck pain in both clinical practice and research.
What does the NDI measure?
The NDI measures how neck pain affects a person's ability to manage everyday activities, capturing a single dimension often described as physical disability related to the neck. It is used for a range of neck conditions, including mechanical neck pain, whiplash-associated disorders, and cervical radiculopathy.
What questions are included in the NDI?
The ten items cover pain intensity, personal care, lifting, reading, headaches, concentration, work, driving, sleeping, and recreation. For each item the respondent selects the one statement, from six options, that best describes their current situation.
How is the NDI scored?
Each item is scored from 0 (no disability) to 5 (complete disability), and the item scores are summed for a total from 0 to 50, where higher scores indicate greater disability. The result can also be doubled and expressed as a percentage from 0 to 100. A commonly cited interpretation is: 0 to 4, no disability; 5 to 14, mild; 15 to 24, moderate; 25 to 34, severe; and 35 or above, complete disability. A change of about 5 points (10%) is generally regarded as the minimal clinically important difference.
How is the NDI used in clinical practice?
Clinicians use the NDI to establish a baseline and to track change over a course of care, and it is often recommended to be administered at baseline and roughly every two weeks during treatment. It has demonstrated good reliability and validity across neck-pain populations and is frequently used to evaluate the effect of interventions.
Strengths and limitations
The NDI's strengths are wide adoption, brevity, and strong measurement evidence. Limitations include possible floor and ceiling effects at the extremes of the scale, so when a baseline score is very low or very high, supplementing the NDI with an additional measure such as a patient-specific functional scale is sometimes recommended.
Frequently asked questions
What is the maximum NDI score? The raw score ranges from 0 to 50, which can also be expressed as 0 to 100%.
What NDI score is considered moderate disability? A raw score of 15 to 24 (30% to 48%) is commonly interpreted as moderate disability.
What change in NDI is meaningful? A change of about 5 points is generally considered clinically meaningful.
References
- Vernon H, Mior S. The Neck Disability Index: a study of reliability and validity. Journal of Manipulative and Physiological Therapeutics. 1991;14(7):409-415.
- Vernon H. The Neck Disability Index: state-of-the-art, 1991-2008. Journal of Manipulative and Physiological Therapeutics. 2008;31(7):491-502.
- MacDermid JC, Walton DM, Avery S, et al. Measurement properties of the Neck Disability Index: a systematic review. Journal of Orthopaedic & Sports Physical Therapy. 2009;39(5):400-417.
