The most common cause for childhood disability in Europe is cerebral palsy (CP). Permanent disturbances of movement, gait and posture are caused by this non-progressive neurologic disorder. Surgeries that correct deformities of muscles and bones of the lower limbs are a common treatment. The mobility of patients after these interventions can improve even more, if the individual muscle functions of a patient are known in advance. Goal of this dissertation is to investigate the crouched gait of children with CP on a level of individual muscle analyses according to biomechanical calculations using individual models based on radiology data. A secondary goal of this thesis is the development of methods that can help to pave the way for using muscle specific biomechanical analysis in clinical routine. Musculoskeletal lower-limb models of two children with cerebral palsy were created together with five models of a control group of normally developing children. Here a newly developed method was applied that facilitates the generation of models that incorporate of individual subject's geometry with the appropriate parameterization of the modelled muscles. The method and the generated models are validated by comparing simulated maximum isometric joint moments to dynamometric measurements. Additionally a combination of the data of the control group is used to describe the first available generic biomechanical model for children. The individual models are used to calculate the time histories of leg-muscle forces and their contribution towards joint moments as well as to joint and centre of mass accelerations. These results provide insight into muscle coordination during gait of normally developing children and of crouch gait in children with cerebral palsy. Analysis of particular muscle functions show the capability of such simulation methods to provide additional diagnostic information that can help to improve the treatment of children with cerebral palsy.