The biomaterial potential of many calcium phosphates, such as hydroxyapatites and tricalcium phosphates (Ca3(PO4)2, TCP hereafter), have led to much literature attention over the past few decades. The α-TCP phase, which is only metastable at ambient conditions since it has to be quenched from high temperatures, is particularly suited to biomaterial applications. Doping α-TCP with silicon stabilises the alpha phase, and makes synthesis easier. However, the local structural disorder that is introduced as a result of silicon doping is not fully understood, and is critical to furthering understanding of how the alpha structure is stabilised, and how the material interfaces with biological systems. Our aim, therefore, is to use pair-distribution function analysis to study the local structure of silicon-doped α-TCP.