Objective: To examine the influence of determinants on the Shoulder Pain and Disability Index.
Design: A cross-sectional study. Baseline registrations were applied.
Patients: Two hundred patients with subacromial shoulder pain lasting at least 3 months.
Methods: A questionnaire consisting of possible determinants, 2 independent variables regarding pain and 2 regarding function, and the outcome measurement. Two multiple regression models (one with and one without the independent variables of pain and function) for the Shoulder Pain and Disability Index, the 2 subscales, and the determinants, were performed.
Results: The included determinants explained 29% of the variance of the Shoulder Pain and Disability Index (25% for pain and 33% for disability subscale) with pain medication, emotional distress, flexion, and the hand-behind-back range accounting for 26%. When pain and function were included, the final model explained 65% of the variance, with gender, education and range of flexion showing significance.
Conclusion: The determinants explained 26% of the variance of the Shoulder Pain and Disability Index, but explained only a minor proportion when pain and function were included. This supports the Shoulder Pain and Disability Index as a shoulder pain and disability questionnaire.