Inflammation of the bony area (tailbone or coccyx) located between the buttocks is referred to as coccydynia. Coccydynia is associated with pain and tenderness at the tip of the tailbone between the buttocks. The pain is often worsened by sitting.
Coccydynia is often caused by an injury, but may occur seemingly spontaneously. There are many causes of tailbone pain which can mimic coccydynia, including sciatica, infection, pilonidal cysts, and fractured bone.