This chapter discusses the sensory cutaneous anatomy of the buttock and outer thigh (and part of the perineum and the pilonidal sinus area). There is a consideration of the landmark anatomy of the piriformis muscle (along with the glutei, obturator internus and gemelli and the quadratus femoris). The component parts of the innominate bone are evaluated with their muscle origins and insertions (along with the embryological separation of the limb compartments as pubic, ischiadic and ilial). The hip joint is discussed as are the operative approaches to the joint from an anatomical access perspective.