Coccydynia

Coccydynia means pain in the coccyx — the tailbone, the small triangular bone at the very bottom of the spine. It is made up of three to five segments that are usually fused into a single piece, and the uppermost segment meets the sacrum at the sacrococcygeal joint. The name reflects an old observation that the bone, viewed from the side, resembles a cuckoo's beak. Coccydynia is best understood as a symptom rather than a single disease, because many different things can produce the same complaint. Reassuringly, most cases settle — often on their own — and around nine in ten respond to simple, non-surgical measures.

Although small, the tailbone earns its place. When a person sits and leans back, body weight rests on a tripod formed by the two "sit bones" and the coccyx, so the tailbone is one of three points taking the load. It also anchors several muscles and ligaments of the pelvic floor, including the levator ani. The joints between the coccygeal segments vary from person to person — some contain a disc, others a more mobile joint — which partly explains why the bone behaves differently in different people. This load- bearing role is the reason pain is typically brought on by sitting, especially leaning back, and by the moment of standing up.

The single most common cause is a fall onto the bottom; a direct knock of this kind is present in roughly half to two-thirds of cases. Childbirth is another well-recognised cause, particularly difficult or instrument-assisted deliveries, because of the pressure the tailbone takes during birth. There is also a slower-developing form linked to long periods sitting on hard or narrow surfaces, a kind of repeated minor strain.

Beyond injury, the shape and mobility of the bone matter. Some tailbones curve or angle forward more sharply, some are subluxated — slightly out of line at a joint — and some carry a small bony spur at the tip that can rub and irritate the surrounding tissue when sitting. The way the coccyx moves also varies: it may bend a normal amount, bend too far (hypermobility), slip backward when sitting and return on standing (luxation), or barely move at all. Excess movement and slippage are both recognised as abnormal, and a stiff coccyx with a spur is its own pain pattern. Degeneration of the small joints can contribute too.

Tailbone pain is about five times more common in women than in men, partly because of differences in pelvic shape and the effects of childbirth, and carrying extra weight adds to the pressure on the area by changing how the pelvis tilts when sitting. Less often, the pain actually arises elsewhere and only feels as though it is in the tailbone — the lower back, the sacroiliac joints, and the pelvic floor are common sources. In a small number of cases there is a more specific underlying cause, such as infection, inflammation, or a tumour, which is one reason a proper assessment is preferable to self-diagnosis.

The classic pattern is pain that can be pinpointed low down at the tailbone, worse when sitting, worse still when leaning back, and often with a sharp twinge on standing up. Some people notice it during bowel movements. On examination, tenderness directly over the bone is the typical finding, and that local soreness helps distinguish a genuinely sore tailbone from pain referred from elsewhere.

The diagnosis is frequently made from the history and examination alone. When imaging is helpful, plain X-rays are usually the starting point, to check the shape of the bone and rule out other problems. A particularly useful technique is to take X-rays both standing and sitting and compare them, because the trouble often appears only when the bone is under load; this can show whether the coccyx is too mobile, slipping, or too stiff. If those do not explain the pain, an MRI scan can reveal inflammation in and around the bone — and the occasional cyst or tumour — that ordinary X-rays may miss.

Treatment follows a stepwise ladder: begin with the gentlest measures and progress only if needed. Most people never move far up it. The first steps are straightforward and often effective — taking pressure off the area with a wedge-shaped cushion (the type with a cutout at the back, rather than a donut shape, which can press on the wrong spot), adjusting sitting posture, and using simple anti-inflammatory measures. Physiotherapy can help, especially when tight pelvic-floor muscles contribute, and may include hands-on techniques to ease muscle spasm or to gently mobilise a stiff tailbone.

If pain persists, injections may be considered. A steroid and local anaesthetic can be placed at the joint under image guidance, both to relieve pain and to confirm where it is coming from. A small nerve bundle that sits just in front of the tailbone can also be targeted — blocking it, or treating it with pulsed radiofrequency, can reduce pain for several months, though benefit tends to lessen with repeated procedures. A good response to an injection can also help indicate who might do well with surgery if it ever becomes necessary.

Surgery to remove the tailbone, an operation called coccygectomy, sits at the top of the ladder and is used only as a last resort, for people whose pain is genuinely disabling and who have not responded to other measures. The coccyx may be removed partially or completely; removal generally proceeds from the joint with the sacrum downward, a direction that tends to give better results and fewer complications than working from the tip upward. Outcomes are good or excellent in roughly 80 to 90 per cent of carefully selected patients. Results are usually better in people whose pain followed trauma or childbirth than in those whose pain is idiopathic — with no clear cause — or bound up with back problems, and careful selection of who is likely to benefit matters more than the surgical technique itself.

Because the operation sits in an awkward spot, close to the back passage, the main concern is the wound. Reduced blood supply and nearness to the anus mean wound infection is the most common complication, usually superficial and treatable, while serious injury to nearby structures is rare. To address this, a minimally invasive endoscopic coccygectomy has been developed. Using a camera and small instruments, the surgeon works through a much smaller opening, shrinking the incision from around two inches to under a centimetre, and can place it slightly away from the highest-pressure point. The aims are better wound healing, lower infection rates, and a lower chance of injuring structures in front of the tailbone, with magnified views improving precision. This approach is promising but still early in its evidence, reported so far in only a small number of cases.

The thread running through all of these options is the same: match the treatment to the cause, allow time, and remember that for most people the condition improves well before surgery is ever considered.

This page is for general information and education only. It is not medical advice and is not a substitute for assessment by a qualified clinician. Anyone with tailbone pain — and especially anyone with warning features such as spreading pain, changes in bladder or bowel control, saddle numbness, or steadily worsening symptoms — should seek an in-person assessment.

• —NICE — Low Back Pain and Sciatica in Over 16s (NG59)
• —NHS — Spinal Conditions
• —British Association of Spine Surgeons (BASS)

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.