The Neck Disability Index (NDI) is a patient-completed, condition-specific functional status questionnaire with 10 items including pain, personal care, lifting, reading, headaches, concentration, work, driving, sleeping and recreation. Each section is scored on a 0 to 5 rating scale, in which zero means 'No pain' and 5 means 'Worst imaginable pain', with the points summed to a total score. The test can be interpretated as a raw score, with a minimum score of 0 and a maximum score of 50. A higher score indicates more patient-rated disability. To use the NDI for patient decisions, a clinically important change was calculated as 5 points.