3DThree-dimensional BCP Children with bilateral cerebral palsy CTD Children with typical development MDF Maximum dorsiflexion UCP Children with unilateral cerebral palsy AIM Calf muscle growth in children with unilateral cerebral palsy (UCP) and bilateral cerebral palsy (BCP) is unknown. This cross-sectional study examines the medial gastrocnemius growth rates of ambulatory children with UCP and BCP compared with children with typical development (CTD), aged 2 to 9 years. METHOD Fifty children with UCP (mean age 66mo [SD 18], 29 males, Gross Motor Function Classification System [GMFCS] I=32, II=18), 50 children with BCP (age 64mo [SD 19], 31 males, GMFCS I=21, II=29), and 78 CTD (age 64mo [SD 16], 40 males) participated in the study. The medial gastrocnemius muscle volume was measured at rest using a validated freehand three-dimensional (3D) ultrasound method.RESULTS Normalized medial gastrocnemius muscle growth rate was significantly less in the children with UCP (0.001 mL/kg/mo) compared with the BCP (0.015 mL/kg/mo, p=0.001) and CTD (0.014 mL/kg/mo, p<0.001) groups. Normalized medial gastrocnemius muscle growth rate was the same in the BCP and CTD groups (p=0.77).