A bruised tailbone can be caused either by an abrupt trauma, such as a fall, or by a less severe but repetitive injury to the area, such as caused by regular cycling or horseback riding. The tailbone is the common name for the coccyx, the fused bone at the base of the spine. As it is a relatively superficial bone, meaning that it lies close to the skin and is unprotected by dense layers of muscle and fat, it is susceptible not only to bruises but to fractures. Women are more likely to suffer a broken or bruised tailbone as the female pelvis is spread wider than the male pelvis, leaving the coccyx vulnerable. In addition, women can suffer a tailbone injury during childbirth due to the strain of the baby exiting the birth canal.
Made up of anywhere from three to five vertically fused vertebrae, the coccyx is widest at the top and tapers toward the bottom, forming a triangle. It is found at the bottom of the vertebral column beneath the sacrum and between the hipbones at the back of the pelvis, and it can be felt between the buttocks. When seated and leaning back slightly, the tailbone forms a kind of tripod with the paired ischium bones on the bottom of the pelvis, allowing a person to maintain her balance in this position.
As the coccyx is the bone upon which much of a person’s weight rests when sitting, a fall backward into a seated position can easily injure this bone. A bruised tailbone, while not necessarily a severe injury, can be extremely painful, cause visible discoloration, and be slow to heal. In addition to limiting one’s ability to sit and/or walk, this injury can make bowel movements extremely painful and therefore interfere with normal functioning.
Any form of direct trauma to the area can cause a bruised tailbone, from a fall backward to a blow to the posterior pelvis, as may be caused by a contact sport like football or rugby. Similarly, a milder but repetitive trauma can result in a bruised tailbone. The stress of cycling, riding a horse, or other seated activity placing too much pressure on the coccyx can cause bruising. Lastly, giving birth or even just carrying pregnancy weight can lead to this injury in women, whether from spending time sitting with so much extra weight on the tailbone or from the stress of labor itself.