SERs (Short External Rotators) of the hip are made up of a number of small muscles that help to rotate the leg outward.  In the posterior approach to the hip (my common approach) I take down the SER tendons and then repair them back to the femur at the end of the operation.  Post op we need to be a bit careful with external rotation but a few months after surgery it is important to work really hard at strengthening these muscles.  Below is an exercise to help improve SER strength.