A good implant primary stability is closely associated with long-term success of total hip arthroplasty. Excessive interfacial micromotion around the femoral component after cementless hip replacement is related to aseptic loosening of the stem and affects the primary fixation of the implant. Finite elements (FE) models are able to predict a complete map of interfacial micromotion. However, due to the difficulty to measure implant micromotion directly at the interface, these models lack validation. Recently, a micro-CT based technique was developed to measure interfacial bone-implant micromotion at multiple points around the femoral stem during compression and torsion. In this project, a FE model of interfacial micromotion around a femoral stem will be developed. Compressive and torsional loading will be considered and the results obtained with the FE model will be compared with the available experimental measurements.