Pain at the base of your spine usually comes from the coccyx (tailbone), the sacrum (the triangular bone just above it), or the joints and muscles connecting them. The most common cause is direct trauma, like falling backward onto a hard surface, but prolonged sitting, pregnancy, and joint problems can all produce that deep, localized ache. Most cases resolve with conservative care over weeks to months, though some causes need closer attention.
What’s Actually at the Base of Your Spine
The base of the spine is made up of two structures: the sacrum, a broad fused bone that connects to your pelvis, and the coccyx, which sits below it. The coccyx is typically three to five small bony segments, with four being the most common. These segments connect to the sacrum through a fibrocartilaginous joint that can stiffen or fuse with age. A network of nerves called the coccygeal plexus runs through this area, which is why even minor problems here can produce surprisingly sharp pain.
On either side of the sacrum, the sacroiliac (SI) joints connect the spine to the hip bones. These joints absorb force when you walk, sit, or twist. Pain from the SI joints is frequently mistaken for tailbone pain because it radiates to the same general area.
Trauma and Falls
A backward fall is the single most common cause of tailbone pain. Landing on a hard surface can bruise, dislocate, or fracture the coccyx. The pain is usually immediate, worst when sitting, and can linger for weeks or months depending on severity. You’ll typically feel it as a sharp, focused ache right at the bottom of the spine that intensifies when you lean back in a chair or transition from sitting to standing.
Internal trauma during childbirth is another frequent cause, particularly in difficult or instrument-assisted deliveries. The coccyx sits directly behind the birth canal, and the pressure of delivery can shift or injure it.
Prolonged or Repetitive Sitting
You don’t need a dramatic injury to develop this pain. Sitting for long periods on hard, narrow, or poorly designed surfaces puts repeated low-grade stress on the coccyx. Cyclists, rowers, office workers, and anyone who sits on hard benches regularly can develop gradual-onset tailbone pain without any single triggering event. The onset is often insidious, starting as mild discomfort that slowly worsens over weeks.
If sitting is the culprit, a U-shaped or modified wedge-shaped cushion can help by taking direct pressure off the coccyx. These cushions have a cutout at the back that lets the tailbone “float” rather than bearing your weight.
Sacroiliac Joint Dysfunction
The SI joints are a commonly overlooked source of pain that feels like it’s coming from the base of the spine. SI joint dysfunction can produce deep, one-sided pain in the lower back or buttock that sometimes spreads down the leg. It’s often worse with prolonged standing, climbing stairs, or rolling over in bed.
Diagnosing SI joint pain can be tricky because it mimics other conditions. Clinicians use a set of physical provocation tests to narrow it down. One you can even try at home: sit in a chair, cross the ankle of your painful side over the opposite knee, and gently push your raised knee down while leaning back. If this reproduces your familiar pain in the buttock area, the SI joint may be involved. In a clinical setting, positive responses to at least three provocation tests suggest SI joint dysfunction, sometimes confirmed with a local anesthetic injection into the joint.
Disc Problems at L5-S1
The lowest disc in your spine sits between the last lumbar vertebra (L5) and the top of the sacrum (S1). This disc bears enormous compressive force and is one of the most common sites for herniation. When it bulges or ruptures, it can compress nearby nerve roots, producing pain at the base of the spine that often radiates into the buttock or down one leg.
Back pain combined with shooting leg pain (sciatica) is the classic pattern. The pain tends to worsen with bending forward, coughing, or sneezing. Large herniations at this level can also affect a nerve network that sits in front of the sacrum, which in rare cases causes bladder or bowel symptoms rather than the typical pain pattern.
Pelvic Floor Muscle Spasms
A less recognized cause is spasm of the levator ani muscle, a broad muscle that forms the floor of your pelvis. When this muscle goes into spasm, it can produce sporadic pain in the rectal area and near the tailbone. This is sometimes called levator syndrome, and coccyx pain is considered a variation of it. The pain tends to come and go, often feels like a dull ache or pressure deep in the pelvis, and can be triggered or worsened by sitting. It’s more common than many people realize and often goes undiagnosed because imaging looks normal.
Pregnancy and Hormonal Changes
During pregnancy, your body produces a hormone called relaxin that loosens the muscles and ligaments around the pelvis, back, and abdomen. This loosening is necessary to accommodate a growing baby and prepare for delivery, but it can destabilize the joints at the base of the spine. The result is pregnancy-related pelvic girdle pain, felt across one or both sides of the lower back, sometimes concentrated right at the tailbone.
This effect compounds as the pregnancy progresses and the center of gravity shifts forward, changing posture and increasing the load on the sacrum and coccyx. The pain usually improves after delivery as relaxin levels drop and ligaments tighten again, though women who experience coccyx injury during birth may have a longer recovery.
Other Contributing Factors
Several less common causes can also produce pain at the spine’s base. Degenerative joint or disc disease in the sacrococcygeal joint develops gradually with age. Abnormal coccyx shape or curvature, which varies significantly from person to person, can make the area more vulnerable to pressure. Infections, though rare, can affect the coccyx or surrounding tissue. In some cases, no clear cause is ever identified.
How This Pain Is Typically Treated
Most tailbone and lower sacral pain responds to conservative measures. The standard approach combines avoiding prolonged sitting on hard surfaces, using a coccyx-cutout cushion, applying ice or heat, and taking over-the-counter anti-inflammatory medication. Physical therapy focused on pelvic floor relaxation and gentle stretching can help, especially when muscle tension is part of the picture.
Conservative treatment is usually given at least six months before anything more aggressive is considered. Most people improve significantly within that window. For those who don’t, options include targeted injections to reduce inflammation around the joint or nerves. Surgery to remove part or all of the coccyx (coccygectomy) is a last resort, reserved for cases that have failed everything else. When it is performed, the results can be dramatic: patients in one recent case series went from pain scores of 8 or 9 out of 10 before surgery to 0 or 1 out of 10 within six weeks. Wound healing typically takes about two weeks.
When the Pain Signals Something Serious
Cauda equina syndrome is a rare but serious condition where the bundle of nerves at the base of the spinal canal becomes severely compressed, usually by a large disc herniation. It requires emergency treatment to prevent permanent damage. The warning signs to watch for are numbness in the groin or inner thighs (sometimes called “saddle numbness”), new difficulty urinating or loss of bladder control, bowel incontinence, and weakness in both legs. In a study of 256 patients with cauda equina syndrome, urinary or fecal incontinence was present in about 35% of cases. If you develop any combination of these symptoms alongside your back pain, seek emergency care immediately.