The pelvic bone is actually a paired set of bones called the os coxae that comprise the pelvic ring. Each os coxae develops from three bones that grow together called the ischium, illium, and pubis, according to the University of Arkansas Medical School 5. On the backside of the pelvis, the two os coxae meet a portion of the spinal column called the sacrum and form a joint called the sacroiliac joint. The two os coxae wrap around the front to form another joint called the symphysis pubis. Since the pelvis is such a large structure, dysfunction and pain can be caused from a number of different things.

Ankylosing Spondylitis

Ankylosing spondylitis, or AS, is a chronic inflammatory condition that causes stiffening of the spinal joints and other joints of the body 1. The inflammation can actually lead to new bone growth and cause fusing of the joints. According to Spondylitis.org, the hallmark feature of ankylosing spondylitis is its involvement of the sacroiliac joints 1. Many people with AS are diagnosed with the disease when seeking treatment for pain in the sacroiliac region or low back.

Sprain Strain

The sacroiliac joint is a movable joint that is covered by a large number of ligaments and muscles, making it susceptible to a sprain strain injury 3. In this type of injury, the muscles are torn to some degree and the ligaments are either overstretched or torn. Ligaments support or stabilize the joint and, when injured, can lead to joint instability and other symptoms. Sprain strain injuries usually are caused by some sort of trauma such as a sports injury, automobile accident or slip and fall accident 3.

Fracture

With a severe traumatic injury, it is possible to fracture the pelvic bone in a number of different locations. In some cases, a severe muscle strain may actually cause an avulsion fracture where the muscle is pulled away from the bone and fractures a piece of the pelvis in the process. Growing teens, especially those involved in sports, and elderly people with osteoporosis are two groups that are especially susceptible to pelvic bone fractures, according to the American Academy of Orthopedic Surgeons 4. A broken pelvis is very painful and is likely to be swollen and bruised, but usually heals well with surgical care.

Cancer

According to the National Cancer Institute, chondrosarcoma and Ewings sarcoma are two bone cancers that most commonly occur in the pelvis 2. Primary bone cancer, or the type of cancer that begins in the bone, is rare, but cancer from other organs can spread to the pelvic bone and cause pain and become life-threatening.