Pressure sores are usually caused by unrelieved pressure on the skin. They often develop on skin that covers bony areas. Places on the body that are at risk for developing pressure sores include the back of the head and ears, shoulder, elbow, the lower back and buttocks, hip, and heel. The greater trochanter (say "troh-KAN-ter"), which is the side of the upper thigh, and the inner knees are also at risk.