Red flags
- *CAUDA EQUINA SYNDROME - a surgical emergency, hours not days*
- New urinary RETENTION with overflow incontinence (the most reliable feature)
- SADDLE ANAESTHESIA (S2-S4) - ask directly; patients do not volunteer it
- Faecal incontinence / loss of anal tone
- BILATERAL leg pain, weakness or numbness
- Progressive neurological deficit
- MALIGNANCY
- Age >50 (or <20), known cancer, unexplained weight loss, night pain not relieved by position, failure to improve over 4-6 weeks
- Breast, prostate, lung, thyroid, kidney, myeloma - the bone-seeking primaries
- INFECTION - vertebral osteomyelitis, discitis, epidural abscess
- Fever, rigors, IV drug use, recent bacteraemia/endocarditis, indwelling line, immunosuppression, diabetes, recent spinal procedure
- *Point bony tenderness plus fever - image urgently*
- FRACTURE
- Trauma (or minimal trauma in the elderly), osteoporosis, prolonged CORTICOSTEROID use, age >70
- INFLAMMATORY (axial spondyloarthritis) - not an emergency, but routinely missed for a decade
- Abdominal or vascular catastrophe presenting as back pain
- *RUPTURING AAA - older, vascular risk factors, tearing pain, hypotension, pulsatile mass*
- Aortic dissection, pancreatitis, perforated ulcer, pyelonephritis, renal colic, ectopic pregnancy, retroperitoneal haemorrhage
Differential by mechanism
Mechanical / non-specific (~90-95%)
- Non-specific low back pain - no identifiable pathoanatomic source; the default and the correct label
- Lumbar disc prolapse with radiculopathy - dermatomal pain below the knee
- Facet joint pain - extension and rotation worse
- Spondylolysis / spondylolisthesis - young athlete (pars defect), or degenerative in the elderly
- Lumbar canal stenosis - neurogenic claudication: worse walking DOWNHILL and on extension, relieved by flexion, "shopping trolley sign"
- Sacroiliac joint pain; vertebral compression fracture
Inflammatory
- Axial spondyloarthritis / ankylosing spondylitis
- Psoriatic, enteropathic (IBD) and reactive spondyloarthritis
- SAPHO, diffuse idiopathic skeletal hyperostosis (DISH) (non-inflammatory but radiographically confusing)
Infection
- Vertebral osteomyelitis / discitis - **Staphylococcus aureus commonest*; Brucella, TB (Pott disease)* in endemic/migrant populations
- Epidural abscess - back pain -> radicular pain -> weakness -> paralysis; the progression is the clue
Neoplastic
- Metastasis (breast, prostate, lung, kidney, thyroid), MYELOMA, lymphoma
- Primary bone tumour, intradural tumour
Metabolic / bone
- Osteoporotic vertebral fracture, osteomalacia, Paget disease, hyperparathyroidism
Referred / visceral
- AAA, aortic dissection, pancreatitis, peptic ulcer, renal colic, pyelonephritis, endometriosis, prostatitis, retroperitoneal pathology
Non-organic amplifiers
- Central sensitisation, yellow flags (see history)
Focused history1 exam ›
Characterise the pain
- Onset - sudden (fracture, disc, vascular) vs insidious (inflammatory, tumour, degenerative)
- Radiation - below the knee in a dermatomal pattern = radiculopathy; above the knee is usually referred somatic pain
- Aggravating and relieving - flexion vs extension; relief on sitting/flexion suggests stenosis
- Night pain - unrelieved by position change is the concerning kind
Inflammatory back pain - ASAS criteria (>=4 of 5)
- Age of onset <45
- Duration >3 months
- Insidious onset
- Morning stiffness >30 minutes
- Improvement with EXERCISE but NOT with rest
- Pain waking in the SECOND HALF of the night
- ALTERNATING BUTTOCK pain
Screen every red flag explicitly
- *Bladder and bowel function, saddle sensation, sexual function - ask; do not wait to be told*
- Fever, rigors, weight loss, night sweats
- Known malignancy; prostate/breast symptoms
- Trauma; corticosteroid use; prior fragility fracture
- IV drug use, recent infection, indwelling device, immunosuppression, diabetes
Spondyloarthritis features
- Psoriasis, IBD, uveitis, dactylitis, enthesitis (heel pain), peripheral arthritis, preceding GI/GU infection, family history of SpA
Yellow flags - the strongest predictors of chronicity
- Belief that the pain is harmful or disabling; fear-avoidance
- Catastrophising, low mood, poor coping
- Work dissatisfaction, compensation or medicolegal claim
- Passive expectation of treatment, prolonged rest, prior prolonged episodes
- *Identify these at the FIRST consultation - they matter more than the imaging*
Focused examination
Look
- Posture, gait, loss of lumbar lordosis, scoliosis or kyphosis, skin (psoriasis, zoster, surgical scars)
Feel and move
- Point bony tenderness (fracture, infection, metastasis) vs diffuse paraspinal tenderness
- Lumbar flexion, extension, lateral flexion, rotation
- Schober test - mark 10 cm above and 5 cm below L5; <5 cm increase on flexion = restricted**
- Chest expansion <2.5 cm - axial spondyloarthritis
- Sacroiliac tests - FABER, sacral compression
Neurological - the part that cannot be skipped
| Root | Motor | Reflex | Sensory |
|---|---|---|---|
| L3/L4 | Knee extension, hip flexion | KNEE jerk | Medial shin |
| L5 | *Dorsiflexion (foot drop), EHL, hip abduction* | None | Dorsum of foot, great toe web |
| S1 | Plantarflexion (test toe-walking), eversion | ANKLE jerk | Lateral foot, sole |
- Straight leg raise (30-70 degrees) - sensitive for L5/S1 radiculopathy; CROSSED SLR is specific
- Femoral stretch test for L2-L4
- *UPPER motor neuron signs (hyperreflexia, upgoing plantars, clonus) = a lesion above the conus - image the whole spine*
- *PR examination for anal tone and saddle sensation if ANY cauda equina feature*
- Post-void bladder scan: >200 mL residual supports retention**
Do not forget
- Abdominal palpation for an expansile mass; femoral and distal pulses - AAA
- Breast, prostate, lymph nodes, skin if malignancy is suspected
- Temperature, injection sites, murmur - infection
Investigation strategy
The default is NO IMAGING
- *Imaging is not indicated for acute non-specific low back pain without red flags*
- Degenerative change, disc bulge and facet arthropathy are present in most asymptomatic adults over 40 - reporting them causes harm: worse outcomes, more surgery, more opioids
- Explicitly discuss why a scan is not being ordered - the Clinical Care Standard makes this a quality indicator
Image when a red flag is present - and choose the right test
| Suspicion | Test |
|---|---|
| *Cauda equina* | *URGENT MRI whole spine - same day, before or alongside surgical referral* |
| Infection (discitis, epidural abscess) | Urgent MRI with contrast + BLOOD CULTURES x2 before antibiotics, CRP, ESR |
| Malignancy / cord compression | MRI whole spine; plus myeloma screen |
| Fracture | X-ray first; CT if X-ray normal and suspicion persists; MRI to date the fracture (marrow oedema) |
| Axial spondyloarthritis | X-ray SI joints, then MRI SI joints (STIR - bone marrow oedema); HLA-B27, CRP |
| Radiculopathy failing 6 weeks of conservative care, or progressive deficit | MRI lumbosacral spine |
Bloods - only if a red flag
- FBE, CRP, ESR (normal inflammatory markers make infection and inflammatory disease less likely but do not exclude them)
- Calcium, ALP, phosphate; EPG/SFLC and urinary Bence-Jones for MYELOMA; PSA
- Blood cultures before antibiotics in suspected spinal infection
- HLA-B27 if inflammatory back pain (prognostic; ~8% of the population is positive)
- CT-guided or open biopsy for suspected discitis before antibiotics, unless the patient is septic
Management
A. Red flag present -> treat the cause
- Cauda equina - urgent neurosurgical referral and decompression; delay beyond 24-48 h substantially worsens bladder and sexual outcome
- Epidural abscess / discitis - blood cultures, biopsy where possible, then IV antibiotics (flucloxacillin, or vancomycin if MRSA risk); neurosurgical review
- Metastatic cord compression - dexamethasone immediately, urgent MRI, radiation oncology/neurosurgery
- Osteoporotic fracture - analgesia, mobilisation, osteoporosis assessment and treatment (this fracture is the sentinel event)
- Axial spondyloarthritis - NSAIDs + exercise, then TNF or IL-17 inhibitor; rheumatology referral
B. Non-specific acute low back pain - the evidence-based script
### 1. Education and reassurance (the most effective intervention)
- "Serious disease is excluded. The natural history is good."
- *Stay active and continue usual activities, including work - bed rest delays recovery*
- Provide a written plan and a reason to return (red flag safety-netting)
### 2. Physical
- Remain active; early return to normal activity and work
- Heat; physiotherapy or structured exercise if not improving by 2-4 weeks
- Manual therapy - modest, short-term benefit only
### 3. Analgesia - regularly, not on demand
- Paracetamol (evidence is weak, but it is safe - first step)
- NSAIDs - the most effective simple analgesic; shortest effective course, with GI/renal/cardiovascular caution
- Opioids - only in carefully selected patients, lowest dose, shortest duration, with a stop date
- *AVOID: gabapentinoids, benzodiazepines and antidepressants for acute low back pain* - the Clinical Care Standard recommends against all three
- Muscle relaxants - limited and short-lived benefit, sedation
### 4. Review
- Reassess at 2-4 weeks; escalate if not improving or if new red flags appear
- Address yellow flags early - psychologically informed physiotherapy, CBT, graded activity
C. Radiculopathy
- Most settle with conservative management over 6-12 weeks
- Epidural corticosteroid injection - short-term relief of leg pain only
- Surgery (discectomy) if progressive neurological deficit, cauda equina, or disabling radicular pain failing 6-12 weeks - faster relief, but similar outcomes at 1-2 years
D. Chronic (>12 weeks)
- Multidisciplinary biopsychosocial rehabilitation
- Duloxetine may help; avoid opioids
- Fusion surgery for non-specific back pain has poor outcomes
Traps
- *Not asking about bladder, bowel and saddle sensation.* Cauda equina is missed by omission, not by misinterpretation
- *"The MRI was normal, so it isn't serious." - a plain X-ray is normal in early discitis, early metastasis and most fractures in the first 2 weeks*
- *Imaging without a red flag* - incidental degenerative findings generate fear, further imaging, injections and surgery, and predict a worse outcome
- Attributing pain to a disc bulge seen on MRI - present in most asymptomatic adults
- *The elderly patient with "new back pain" and vascular risk factors* - palpate the abdomen; think AAA and dissection
- Missing inflammatory back pain in a young adult - average diagnostic delay in axial SpA is still 5-8 years; the discriminator is improvement WITH exercise and NOT with rest, plus night pain in the second half of the night
- Missing myeloma - "osteoporotic" vertebral collapse in a man, or with anaemia, raised ESR, renal impairment or hypercalcaemia
- Normal CRP does not exclude spinal infection or malignancy
- *Prescribing an opioid at the first visit* - the strongest modifiable predictor of long-term opioid use
- Ignoring yellow flags - they predict chronicity better than any imaging finding
- Forgetting that a fragility fracture mandates osteoporosis treatment - the commonest missed secondary prevention opportunity in medicine
- Herpes zoster before the rash appears - dermatomal burning pain with allodynia
Talk track
1. Exclude the emergency first
- "My first job is to exclude cauda equina syndrome, so I ask specifically about urinary retention, saddle numbness and bowel control, and I examine anal tone and perianal sensation. If any of those are present this is an urgent MRI and a neurosurgical call today."
2. Then work through the red flag categories
- "I screen systematically for infection, malignancy, fracture, inflammatory disease and a vascular cause - so, fever and injecting drug use, weight loss and known cancer, trauma and steroids, inflammatory features, and in an older patient I palpate the abdomen for an aneurysm."
3. Name the diagnosis positively
- "In the absence of red flags this is non-specific low back pain, which is a positive diagnosis, not a failure to find something. Ninety per cent settle substantially within six weeks."
4. Justify not imaging
- "I would not image. The Australian Clinical Care Standard specifically recommends against it without red flags, because degenerative change and disc bulges are near-universal over forty and reporting them leads to worse outcomes, more opioids and more surgery. I would explain that to the patient rather than just refusing the scan."
5. Management is activity, not rest
- "Education and reassurance, staying active and at work, regular simple analgesia - NSAIDs if there is no contraindication. I would avoid gabapentinoids, benzodiazepines and antidepressants, and I would be very cautious with opioids, with a stop date if I used one."
6. Look for what predicts chronicity
- "At the first visit I also assess yellow flags - fear-avoidance, catastrophising, work issues - because those predict who becomes chronic far better than anything on a scan, and they are what I would target with a psychologically informed rehabilitation program."
7. Safety-net
- "I give a written plan, review at two to four weeks, and tell the patient exactly which symptoms mean they come back the same day.
8 of 8 sections written · drafted 2026-09-11