Currently, there are more than 30 million amputees in the world and each year thousands of people suffer from amputation and, therefore, the development of lower limb prostheses is crucial to improve the quality of millions of people's lives by restoring their mobility. This contribution proposes a simulated amputee model capable of reproducing a transtibial amputee subject wearing a passive prosthesis. The passive prosthesis behavior is simulated using a spring-damper system between shin and foot. This contribution provides a tool capable of reproducing an amputee subject wearing a passive prosthesis, as well as an adaptive framework where researchers can deploy controllers in the simulated transtibial prosthesis, transforming it in a powered transtibial prosthesis. Results show that the amputee model is good for the simulation of transtibial amputees wearing a passive device or an active transtibial prosthesis.