In total hip arthroplasty, cup anteversion is an important factor in stability. Lewinnek's safe zone and functional anteversion are often used to assess appropriate orientation. However, these approaches do not consider the effect of the spinopelvic chain and lumbar mobility when in the seated position. This study will measure functional anteversion when standing and sitting with patient-specific computer models and define a quantitative relationship between the change in functional anteversion and spinopelvic parameters. This will challenge the historical paradigm of the safe zone and provide a tool to define anteversion based on a patient's mechanics and reduce risk of dislocation.