My 74-year-old mother had a hip replacement in January due to a hip fracture. Four weeks after surgery she began experiencing sharp pains in her thigh. This pain makes it very difficult for her to walk. Could you explain why this pain would suddenly appear four weeks after the surgery? Will it eventually go away?

Thigh pain after hip replacement surgery can come from several sources. Thigh pain can result from pressure on a nerve at the spine from a herniated or bulging disc as well as a bone spur. Often this pressure is felt in the thigh instead of the back. Scarring around the sciatic nerve as it courses through the back of the hip adjacent to the surgical site can be another source of pressure on the nerve producing thigh pain. The hip replacement may also be the source of your mother's thigh pain. An artificial hip is typically made up of a socket and a femoral stem component that fits into the center of the femur. Some artificial hips are secured in the femur with cement. There is less likelihood of thigh pain being produced after surgery when cement is used. When cement is not used, the femoral stem component relies on a tight fit. There are small pores on the side of the femoral stem that allow bone to grow into these small spaces, producing a biologic lock. This process is very much like healing a bone fracture. If the pain persists beyond six months, it may mean that the healing process is not complete enough to produce a biologic lock. This process is needed to adequately secure the hip replacement. If not, loosening may occur, resulting in pain. Careful follow-up and X-rays can help determine if the healing process is progressing or if the stem component has become loose.