Abstract Background: Knee contracture is a frequent problem in cerebral palsy (CP) child due to spasticity. Aim of Study: To determine the effect of therapeutic ultrasound in addition to passive stretching on knee joint range of motion (ROM) in children with HCP (hemiplegic CP). Material and Methods: Sixty HCP children, were suffering from knee joint flexion deformity due to hamstrings muscle tightness and their ages ranged from 4 and 6 years old. They were divided into two equal groups.Control group received traditional treatment in addition to stretching while study group received the same program in addition to therapeutic ultrasound 3 times per week for 3 months. Patients in both groups were assessed by Absolute + AxisTM Digital Goniometer and Growth Motor Function Measure (GMFM-88&66) before treatment and after 12 weeks. Results: There is a strong positive significant correlation between ROM and GMFM post treatment in study group (r=0.95, p=0.0001) when compared with the control group (r=0.85, p=0.0001). Conclusion: There was a signficant improvement in knee ROM and gross motor functions infavour the study group.