What Causes Pain Over the Sacrum and Tailbone Area?
Sacrum pain and tailbone pain, sometimes called coccydynia, usually come from sitting for a long time, a fall, childbirth or problems with pelvic alignment. The sacrum joins the spine to the pelvis. So problems above or below it often refer pain to this spot. A standing whole-body scan can show alignment factors that lying-down imaging misses.
Key takeaways
- The sacrum and coccyx sit at the base of the spine, where your spine meets your pelvis.
- Common causes include falls, sitting posture, childbirth and sacroiliac joint problems.
- Pain here can be referred from lower back pain or a rotated pelvis.
- Standing imaging shows how your posture under body weight loads the sacrum. Lying-down scans cannot capture this.
- EOS imaging uses about 90% less radiation than a standard X-ray, around ten times less.
What are the sacrum and tailbone, and why do they hurt?
The sacrum is a wide, triangular bone at the base of your spine. It is made of five fused vertebrae. Below it sits the coccyx, a small set of fused bones commonly called the tailbone. Together they anchor your pelvis. They pass the weight of your upper body into your hips and legs.
The sacrum joins the pelvis on each side through the sacroiliac (SI) joints. So it is affected by how you stand, sit and move. When pelvic alignment shifts, the sacrum follows. The tailbone can then bear pressure it was never designed to handle alone.
How does sacrum and tailbone pain feel?
The pain is usually a dull ache or sharp tenderness right at the base of the spine. It often gets worse when you sit, especially on hard surfaces. It may ease when you stand or walk. Some people feel it on one side only, which can point to an SI joint dysfunction.
When to consider MRI. EOS imaging shows bones, joints and alignment clearly. If your clinician suspects the soft tissues, a disc or a nerve is involved, MRI is usually the better tool. The two scans work well together.
Important. If you have numbness around the saddle area, loss of bladder or bowel control, or sudden weakness in your legs, seek urgent medical care. Contact your doctor or go to your nearest emergency department straight away.
What causes sacrum pain and coccydynia?
Several things can trigger pain at the base of the spine. Some are obvious, like a fall. Others build up slowly over months or years as sitting habits, pelvic alignment or the way your body moves shift.
In many cases, the body is compensating. The chain from your feet through your knees, hips and pelvis all affects how the sacrum is loaded. A problem in one area can make another compensate. So the source of pain and the cause of pain are not always in the same place.
How does a standing scan help with sacrum and tailbone pain?
A standing scan captures your skeleton under load, exactly as it works in daily life. This matters because lying down for a normal X-ray or MRI lets your muscles relax and your pelvis flatten. Alignment problems that only appear when gravity is involved can simply vanish on a lying-down image.
Weight is on. The scan captures your full spine, pelvis and legs in one image while you stand naturally. Pelvic rotation, leg-length differences and sacral tilt all show up because gravity is doing its job.
EOS technology uses about 90% less radiation than a standard X-ray, around ten times less. That makes it practical for a whole-body assessment.
Weight is off. When you lie flat, your pelvis carries no load. A mild tilt or rotation can correct itself. So the image looks normal, even though your symptoms are very real when you are upright.
Lying-down imaging still has clear value for soft tissue and disc problems. But for alignment, it can miss the bigger picture.
ScanAlign standing EOS imaging captures your full alignment from head to feet in a single scan. This lets a specialist see whether a pelvic tilt, an uneven SI joint or a lumbar curve is putting extra pressure on your sacrum.
What helps with sacrum and tailbone pain?
The right approach depends on the cause. ScanAlign is a diagnostic imaging clinic, so we do not provide treatment. But a clear picture of your standing alignment gives you and your clinician the information needed to choose the most effective way forward.
Before you start a treatment, or change the one you are on, it is worth getting a detailed diagnosis. Knowing whether the cause sits in the pelvis, the legs or the spine changes what will actually help.
- Your sacrum or tailbone pain has lasted weeks or months
- Earlier lying-down imaging showed nothing abnormal
- You suspect a pelvic tilt or leg-length difference
- You sit for long hours and the pain is getting worse
- You want a full alignment picture before seeing a specialist
- You have numbness, weakness or loss of bladder/bowel control (seek urgent care)
- Your pain started with a recent high-impact injury (an emergency department may be the right place)
- You need an assessment of soft tissue or discs (MRI is usually better)
- You are under 18
Not sure whether travelling to London for a standing scan is the right next step? Our free video consultation lets you talk through your symptoms with our team before you commit to anything.
Book a free video consultationFrequently asked questions about sacrum and tailbone pain
Sitting puts direct pressure on the coccyx, especially on hard or flat surfaces. If the coccyx is bruised or slightly out of line, or if the ligaments around it are strained, that pressure causes pain. Sitting slumped makes it worse because more weight shifts to the base of the spine.
They are closely related but not the same. Coccydynia means pain in the coccyx (tailbone) specifically. Sacrum pain sits slightly higher, in the wider triangular bone. Because the two bones are connected, the terms are often used together and the pain can overlap.
Yes. When the pelvis tilts or rotates, the sacroiliac joints on each side are loaded unevenly. This imbalance can strain the ligaments around the sacrum and cause pain on one or both sides. A standing whole-body scan can show whether a rotated pelvis is playing a part.
Absolutely. The lumbar spine sits directly above the sacrum. Disc problems, joint stiffness or tight muscles in the lower back can refer pain down into the sacral area. This is one reason why a whole-body view of your alignment is helpful.
It varies widely. A mild bruise may settle in a few weeks. Coccydynia from a fall or childbirth can sometimes last months. If your pain has not improved after several weeks, it is worth checking whether an alignment problem is keeping it going.
No. ScanAlign is a self-referral clinic, so you can book a standing spine and pelvis scan without a letter from your doctor. You start with a free video consultation to make sure it is the right option for you.
EOS uses about 90% less radiation than a standard X-ray, around ten times less. It captures the full body in a single pass while you stand still for a few seconds.
The price for patients travelling from abroad is confirmed during the free video consultation. ScanAlign is a private, self-pay clinic with no hidden fees.
Yes. The sacroiliac joints are where the sacrum meets the pelvis. Inflammation or dysfunction in these joints is one of the most common causes of sacral pain. You can read more about SI joint dysfunction and how alignment imaging can help.
When you lie flat, gravity no longer acts on your skeleton. Your pelvis settles into a neutral position, your muscles relax and mild tilts or rotations can disappear from the image. A standing scan captures your body under real-life load, so alignment problems that cause sacrum pain are visible.
Find out what is behind your sacrum or tailbone pain
A free video consultation lets you talk through your symptoms with our team from home. No referral needed, no obligation.
Book a free video consultationWritten by Abbas Dhami (Specialist Diagnostic Radiographer)
Sources
- NHS. "Coccydynia (tailbone pain)." nhs.uk, 2023.
- Maigne JY, Doursounian L, Chatellier G. "Causes and mechanisms of common coccydynia." Spine, 2000;25(23):3072-3079.
- Illés T, Somoskeöy S. "The EOS imaging system and its uses in daily orthopaedic practice." International Orthopaedics, 2012;36(7):1405-1411.
This page is general information and not a diagnosis.
ScanAlign is the trading name of CoreMed Solutions Ltd and operates under The Harley Street Hospital's CQC licence.