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.
Study aid only. These notes are written with the help of AI. Not for guiding clinical decisions.