BACKGROUND: Current treatments for low back pain have small effects. A research priority is to identify patient characteristics associated with larger effects for specific interventions. OBJECTIVE: To identify simple clinical characteristics of patients with chronic low back pain who would benefit more from either motor control exercises or graded activity. DESIGN: Randomized controlled trial. SETTING: Australian physiotherapy clinics. PARTICIPANTS: 172 patients presenting with chronic low back pain were enrolled in the trial. INTERVENTIONS: The treatment consisted of 12 initial exercise sessions over an 8-week period and booster sessions at 4 and 10 months following randomization. MEASUREMENTS: The putative effect modifiers (psychosocial features, physical activity level, walking tolerance and self-reported signs of clinical instability) were measured at baseline. Measures of pain and function (both measured on a 0-10 scale) were taken at baseline, 2, 6 and 12 months by a blinded assessor. RESULTS: We found self-reported clinical instability was a statistically significant and clinically important modifier of treatment response for 12 month function (interaction: 2.72; 95% CI 1.39 to 4.06). People with high scores on the clinical instability questionnaire (>/=9) did 0.85 points better with motor control whereas people who had low scores (<9) did 1.93 points better with graded activity. Most other effect modifiers investigated did not appear to be useful in identifying preferential response to exercise type. LIMITATIONS: The psychometric properties of the instability questionnaire have not been fully tested. CONCLUSION: A simple 15-item questionnaire of features considered indicative of clinical instability can identify patients who respond best to either motor control exercise or graded activity.
a1538-6724 (Electronic)