A sacral stress fracture is a common cause of lower back or buttock pain in runners — and one that’s frequently confused with sacroiliac joint or lumbar spine pain. So how do we diagnose a sacral stress fracture, and how is it managed?
What is a sacral stress fracture?
The sacrum is the triangular bone at the bottom of the spine, connecting the spine to the pelvis through the sacroiliac joints. When the load on the sacrum increases — through a rise in training volume or intensity — the bone fatigues, leading to bone stress. This can affect the body of the sacrum or its wings (the ala).
Sacral stress fracture symptoms
Common symptoms are low back or buttock pain, usually worse during or after impact activity such as a running session. As it worsens, the pain is felt even with gentle walking, and pain at rest or at night signals more severe bone stress. Occasionally, the pain radiates into the lower leg, mimicking sciatica.
Alongside the pain, it’s important to consider the training history — a sudden change in the training schedule, improper footwear, or a change of running surface.
On examination, asking the person to hop is key: pain on hopping increases the likelihood of a stress fracture, while pain-free hopping makes it unlikely. There’s usually tenderness over the sacrum, while examination of the sacroiliac joint, lumbar spine, and hip is often normal — which helps point away from those as the source.
How is a sacral stress fracture diagnosed?
We use MRI to confirm or exclude a sacral stress fracture, looking for bone swelling around a fracture line. X-rays and ultrasound usually cannot detect stress fractures in the sacrum — so a normal X-ray does not rule it out.
Sacral bone stress fracture treatment
Treatment centres on rest from running and prolonged walking. If the pain is severe, you may need crutches for a few weeks.
Rest from running is generally at least six weeks, though the exact time depends on the severity at diagnosis. You can maintain aerobic fitness with non-impact activities such as swimming, cycling, and upper-body weights, alongside focused hip and pelvic strengthening.
An important point on painkillers: it’s best to avoid NSAIDs such as ibuprofen with a stress fracture, as recent evidence suggests they may delay bone healing.
As you return to running, we suggest a gradual walk/run programme, or an anti-gravity treadmill.
In some cases we assess bone health with a DEXA scan (bone density) and blood tests, to exclude conditions affecting calcium metabolism or vitamin D deficiency.
Frequently asked questions about a sacral bone stress fracture
Can you walk with a sacral stress fracture?
In milder cases, walking may not be painful. But you should avoid prolonged walking, or walking for fitness, while the fracture heals — the aim is to offload the bone enough for it to recover.
Can a sacral stress fracture heal on its own?
Yes. Most sacral stress fractures settle with relative rest from impact activity such as running. The bone heals well when it’s offloaded, which is why early diagnosis and a period of reduced loading are so effective.
How is it different from sacroiliac joint or back pain?
This is the crucial distinction, because they’re easily confused. A sacral stress fracture causes buttock or low back pain that worsens with impact and eases with rest, with a positive hop test and a normal examination of the SI joint, spine, and hip. Sacroiliac and lumbar problems usually have their own examination findings and aren’t reliably reproduced by hopping. MRI settles it — and it matters, because the treatments are very different.
Do you need further tests once it’s diagnosed?
Sometimes. Where bone health may be sub-optimal, we consider blood tests — vitamin D, B12, folate, ferritin, bone profile, and inflammatory markers — and a DEXA scan to measure bone density. This is especially relevant in recurrent stress fractures or where RED-S is suspected.
Is shockwave a treatment for a sacral bone stress fracture?
Yes. Recent evidence suggests focused shockwave may help bony healing in stress fractures. We generally recommend 3–5 sessions of high-energy focused shockwave alongside the core treatment, and sometimes more during the return to running.
How long does a sacral stress fracture take to heal?
Rest from running is at least six weeks, and often longer depending on severity, before a graded walk/run return. Most runners recover fully with the right offloading and a progressive return to impact.
Final word from Sport Doctor London about a sacral stress fracture in runners
Bone stress of the sacrum is a common cause of low back or buttock pain in runners, and it’s often mistaken for sacroiliac joint or lumbar spine pain. If you think you might have bone stress in your sacrum, see an experienced sports medicine consultant for a prompt diagnosis — the hop test and an MRI usually settle it quickly.
If you have persistent low back or buttock pain with running, Dr Masci can assess you in London, arrange the right imaging, and guide your recovery. Contact the team here or call +44 (0) 203 488 0350.
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