Special tests library › Red flags
Low back and pelvis red flags
What you cannot afford to miss in low back pain, before any special test.
Most low back pain is musculoskeletal. These are the conditions that are not, or that need referral before treatment, with the features that point to each. Every row carries its source, listed at the foot of the page.
Use with your local protocols. Referral pathways, and how urgently to act, differ between health services and countries: where your local protocol or current guideline differs, follow it. Never delay emergency care to check a protocol.
| Can’t miss | What points to it |
|---|---|
| Cauda equina syndrome1 | Saddle (perineal) numbness, new bladder or bowel change (retention, incontinence, altered sensation), new sexual dysfunction, or bilateral leg symptoms. This is a neurosurgical emergency: refer the patient immediately to an emergency department for MRI. Every patient with low back pain should be asked about these features, with or without leg symptoms. |
| Spinal malignancy2,3 | A past history of cancer is the most informative single red flag. Constant or night pain not eased by position, rest or anti-inflammatory medication, and unexplained weight loss add to the concern. Refer for urgent medical assessment and imaging. |
| Spinal infection3 | Fever or malaise, intravenous drug use, immunosuppression, or a recent spinal injection or operation, together with constant pain. Discitis and epidural abscess are easily missed in the early stages. Same-day medical assessment is required. |
| Vertebral fracture2,4 | Older age (over 70), long-term corticosteroid use, known osteoporosis, significant trauma, or bruising or abrasion over the spine. In fragile bone the trauma can be trivial or absent. The presence of several flags together makes fracture likely. Refer for medical assessment and imaging; the bedside signs are described on the thoracic and chest wall red flags page. |
| Abdominal aortic aneurysm5 | Age over 60 with vascular risk factors (smoking, hypertension, known vascular disease) and back or abdominal pain that does not change with movement or position. A pulsatile abdominal mass, or sudden severe tearing pain, is a surgical emergency: call an ambulance. Otherwise, a suspected aneurysm requires urgent medical assessment rather than physiotherapy. |
| Progressive neurological deficit3 | Weakness that is spreading or worsening between visits, or a new foot drop. Refer urgently for medical or surgical review rather than waiting to see whether it settles. |
| Pars stress fracture in a young athlete6 | An adolescent or young adult in extension-loading sport (fast bowling, gymnastics, dance, weightlifting) with unilateral low back pain on extension. The stork test cannot exclude a pars stress fracture; imaging is required to do so. Continued loading risks progression to a complete defect or slip. |
| Sacral stress or insufficiency fracture7 | Buttock or low back pain with little or no trauma in a patient with osteoporosis or corticosteroid exposure, or in a runner after an increase in training load. It is often mistaken for sacroiliac joint pain. The diagnosis is made by imaging, not by a trial of manual therapy. |
| Inflammatory back pain8 | In back pain of 3 months or more: onset before 40, insidious onset, improvement with exercise, no improvement with rest, and night pain that eases on getting up (four or more of these five features suggest inflammatory back pain). This is not an emergency, but the patient should be referred for rheumatology assessment rather than managed as having mechanical back pain. |
| Hip masquerading as back9 | The buttock is the most common area of referred pain from a painful hip. Groin pain, a limp, and painful or restricted hip internal rotation point to the hip as the source: see hip and groin red flags. |
A red flag raises suspicion; it does not make the diagnosis, and its absence does not rule the condition out. The table is not a complete list of every serious condition, and it is not a clinical protocol. When a red flag is present, act on the referral advice in the row, in line with your local protocols. This page is for registered health practitioners and students and is not clinical advice for patients; see the terms of use.
Last checked against the cited sources: 15 October 2026.
Then the tests: Low back and pelvis special tests, with sensitivity, specificity and likelihood ratios.
Get the book for telling radicular leg pain from referred pain, and knowing when cauda equina means send now
This table opens the chapter ‘The low back and pelvis’ in Rule It In, Rule It Out. The book then works through the questions that matter in this region, with the published figures for each test and how to read them.
Coming in late 2026 as a PDF and a paperback. Join the list to hear when it's out
Sources
- Rider LS, Marra EM. Cauda Equina and Conus Medullaris Syndromes. StatPearls Publishing; updated August 7, 2023. Link
- Downie A, Williams CM, Henschke N, et al. Red flags to screen for malignancy and fracture in patients with low back pain: systematic review. BMJ. 2013;347:f7095. Link
- Finucane LM, Downie A, Mercer C, et al. International Framework for Red Flags for Potential Serious Spinal Pathologies. J Orthop Sports Phys Ther. 2020;50(7):350–372. Link
- Han CS, Hancock MJ, Downie A, et al. Red flags to screen for vertebral fracture in people presenting with low back pain. Cochrane Database Syst Rev. 2023;(8):CD014461. Link
- Chaikof EL, Dalman RL, Eskandari MK, et al. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018;67(1):2–77.e2. Link
- Grødahl LHJ, Fawcett L, Nazareth M, Smith R, Spencer S, Heneghan N, Rushton A. Diagnostic utility of patient history and physical examination data to detect spondylolysis and spondylolisthesis in athletes with low back pain: a systematic review. Man Ther. 2016;24:7–17. Link
- Beit Ner E, Rabau O, Dosani S, Hazan U, Anekstein Y, Smorgick Y. Sacral stress fractures in athletes. Eur Spine J. 2022;31(1):1–9. Link
- Sieper J, van der Heijde D, Landewé R, Brandt J, Burgos-Vargas R, Collantes-Estevez E, et al. New criteria for inflammatory back pain in patients with chronic back pain: a real patient exercise by experts from the Assessment of SpondyloArthritis international Society (ASAS). Ann Rheum Dis. 2009;68(6):784–788. Link
- Lesher JM, Dreyfuss P, Hager N, Kaplan M, Furman M. Hip joint pain referral patterns: a descriptive study. Pain Med. 2008;9(1):22–25. Link
Red flags for other regions: Neck · Shoulder · Elbow · Wrist and hand · Thoracic spine and chest wall · Hip and groin · Knee · Ankle and foot
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