A unique approach was undertaken to combine quantitative measurements of human gait, analytical investigation and specification of mechanical components, and computer simulation techniques to design and evaluate a new prototype paediatric above-knee endoskeletal running prosthesis. To overcome the performance restrictions of conventional children's prostheses, prosthetic components were designed to approximate kinematic and kinetic performance of ablebodied subjects. Components were designed to improve knee control and the body's centre-of-mass displacement profile during gait. Quantitative gait measurements of single walking and running subjects were used to provide data for component design and the computer simulation of gait. Three components were proposed to improve child above-knee amputee running:​ a four-bar linkage knee joint, a double-acting knee damper, and a telescoping shank spring-damper. For the first time, computer simulation was used for preliminary' testing and evaluation of a complex above-knee prosthesis over both the swing and support phases of gait. Three-dimensional, direct dynamic computer simulation of an able-bodied individual during walking and running gait was achieved:​ the technique was then applied to simulate both conventional and prototype above-knee prosthetic gait. Limitations to simulation accuracy were due to the exclusion of a neuromuscular control model, and the simplified modelling of foot-ground contact. Kinematic simulation results indicated that the prototype prosthesis demonstrated both performance improvements and weaknesses compared with a conventional children's prosthesis.