Tailbone pain, medically termed coccydynia, involves discomfort in and around the coccyx, the small bone at the very bottom of the spine. The pain can range from a dull ache to a sharp, stabbing sensation, often worsening with activities like sitting or rising from a chair. While many worry that this pain could signal cancer, primary cancer of the coccyx is extremely rare. The vast majority of tailbone pain results from mechanical issues or trauma. This makes it highly likely that the discomfort is due to benign, non-cancerous causes.
The Overwhelming Majority of Tailbone Pain Cases
Most instances of coccydynia are attributed to direct physical trauma or repetitive microtrauma. A sudden fall can bruise, dislocate, or fracture the coccyx, leading to acute pain. This injury causes inflammation and instability in the ligaments and joints connecting the coccyx to the sacrum.
Repetitive strain from activities involving prolonged pressure, such as cycling or extended sitting on hard surfaces, also causes chronic irritation. For women, injury sustained during childbirth is a common cause, as labor can stretch and strain the ligaments around the coccyx. Females are generally five times more likely to develop coccydynia than males, partly due to differences in pelvic structure.
Non-traumatic causes include degenerative changes in the coccygeal joints, similar to osteoarthritis. Obesity is another factor, as a higher body mass index increases pressure on the coccyx when sitting. A significant number of cases are classified as idiopathic, meaning the exact cause cannot be identified, though issues like hypermobility or hypomobility of the joint are often implicated.
Rare Malignancies Associated with Coccyx Pain
While most tailbone pain is benign, a small number of cases are linked to cancerous growths in the sacrococcygeal region. The most significant primary tumor in this area is a chordoma. Chordomas are slow-growing, malignant bone tumors that arise from remnants of the notochord.
Approximately 40% of all chordomas occur in the sacrococcygeal area, making them the most common primary bone cancer of the sacrum and coccyx. This tumor is exceptionally rare, with an incidence of about one new case per million people per year.
Coccydynia can also be a sign of metastatic cancer, which is cancer that has spread from a different site in the body. Cancers originating in the prostate, breast, lung, or colon are known to metastasize to the bones, including the sacrum and coccyx. Colorectal or cervical cancer can also cause pain referred to the tailbone area due to their proximity to the pelvic nerves.
Warning Signs That Warrant Medical Investigation
Certain symptoms, often referred to as “red flags,” suggest that tailbone pain might be caused by a serious underlying condition, such as a tumor or severe infection. Unlike mechanical coccydynia, which is typically relieved by standing or using a specialized cushion, pain caused by a tumor often persists even when lying down.
These warning signs indicate the need for immediate medical attention:
- Pain that is constant and progressive, steadily worsening over time and not fluctuating with position or activity.
- Night pain severe enough to wake a person from sleep and unrelated to movement.
- Systemic indicators such as unexplained weight loss, fever, or night sweats.
- The presence of a palpable, firm mass near the coccyx that can be felt by the patient.
- New onset of neurological changes, including numbness, tingling, or weakness in the legs.
- Difficulty with bladder or bowel control, which suggests a mass is pressing on nerves in the lower spinal column.
Medical Evaluation and Diagnostic Steps
When a patient presents with persistent tailbone pain, the medical evaluation begins with a thorough history and physical examination. The physical exam involves external palpation of the coccyx to check for localized tenderness, swelling, or a mass. A doctor may also perform a digital rectal examination to assess the coccyx’s mobility and check for masses anterior to the bone.
Initial imaging usually involves a standard X-ray to look for fractures, dislocations, or degenerative changes. Dynamic X-rays may be taken while the patient is sitting and standing to check for abnormal movement of the coccyx. If the initial exam or X-ray suggests a tumor, infection, or soft-tissue problem, more advanced imaging is necessary.
A Magnetic Resonance Imaging (MRI) scan is the preferred next step, as it provides detailed images of soft tissues, nerves, and bones, allowing identification of masses like a chordoma. If the MRI suggests malignancy, a biopsy is performed to obtain a tissue sample. The biopsy is the definitive step to confirm cancer and determine its specific type.