STUDY DESIGN: Prospective cohort. INTRODUCTION: Many variables are believed to influence the success of dynamic splinting, yet their relationship with contracture resolution is unclear. PURPOSE OF THE STUDY: To identify the predictors of outcome with dynamic splinting of the stiff hand after trauma. METHODS: Forty-six participants (56 joints) completed eight weeks of dynamic splinting, and the relationship between 13 clinical variables and outcome was explored. RESULTS: Improvement in passive range of motion, active range of motion (AROM), and torque range of motion averaged 21.8°, 20.0°, and 13.0°, respectively (average daily total end range time, 7.96 hours). Significant predictors included joint stiffness (modified Weeks Test), time since injury, diagnosis, and deficit (flexion/extension). For every degree change in ROM on the modified Weeks Test, AROM improved 1.09° (standard error, 0.2). Test-retest reliability of the modified Weeks Test was high (intraclass correlation coefficient [2, 1]=0.78). CONCLUSIONS: Better progress with dynamic splinting may be expected in joints with less pretreatment stiffness, shorter time since injury (<12 weeks), and in flexion rather than extension deficits. Further research is needed to determine the accuracy with which the modified Weeks Test may predict contracture resolution. LEVEL OF EVIDENCE: 2b.