Back Pain History OSCE, Red Flags, Cauda Equina, and Differentials

Why Back Pain History Is High-Yield

Back pain is one of the most common presenting complaints in both primary care and A&E. The history determines whether a patient has simple mechanical pain, inflammatory arthropathy, or a potentially life-threatening sinister cause such as malignancy, infection, or cauda equina syndrome. Missing red flags in an OSCE is an automatic mark loss.

The Core Classification

Before asking about symptoms, have this framework in mind:

SOCRATES for Back Pain

Site:

• "Where exactly is the pain? Can you point to it?"
• Localised lumbar vs thoracic vs cervical
• "Does it spread anywhere?" (radiation to buttock, leg, groin)

Onset:

• "Did it come on suddenly or gradually?"
• Sudden onset after lifting suggests disc herniation
• Gradual onset in a young person with morning stiffness suggests ankylosing spondylitis
• Insidious onset in an older patient with weight loss: red flag for malignancy

Character:

• "What does the pain feel like? Is it a dull ache, a sharp stabbing pain, or a burning sensation?"
• Radicular pain (shooting, burning, electric): suggests nerve root involvement
• Dull ache: typical of mechanical or inflammatory

Radiation:

• "Does the pain go down your leg?"
• Below the knee = true sciatica (L4-S1 nerve root compression)
• Into buttock only = referred pain, less likely discogenic

Severity: 0-10 pain score.

Timing:

• "Is it there all the time or does it come and go?"
• "Is it worse at any particular time of day?"
• Worse in the morning and improves through the day: inflammatory
• Worse with activity and better with rest: mechanical
• Constant, not relieved by rest, worse at night: sinister

Red Flags, Never Skip These

Inflammatory Back Pain: Ankylosing Spondylitis

If the patient is young (under 40), male, with insidious onset, ask:

• "How long does your stiffness last in the morning?" (over 30 minutes is inflammatory)
• "Does exercise or moving around help?" (inflammatory back pain improves with activity)
• "Have you had any eye problems, redness or pain in your eyes?" (uveitis in seronegative arthropathies)
• "Any skin problems?" (psoriasis in psoriatic arthritis)
• "Any bowel problems like bloody diarrhoea?" (IBD-associated arthropathy)
• "Any family history of joint disease?"

Sciatica and Radiculopathy

If pain radiates below the knee:

• "Does it follow a particular path down the leg?"
• "Is there any numbness or tingling?" (paraesthesia suggests nerve root irritation)
• "Any weakness in the leg or foot?" (foot drop: L4/L5)
• Straight leg raise is positive at less than 60 degrees in L4/L5/S1 radiculopathy

Past Medical History

• Previous back surgery or procedures
• Osteoporosis (DEXA scans, previous fractures)
• Cancer history (breast, prostate, lung, renal, thyroid: all metastasise to spine)
• Rheumatological conditions

Social and Functional History

• Occupation: heavy lifting, desk job, vibrating machinery
• Driving: how long, and whether it affects symptoms
• Impact on daily life: "What can't you do now that you could do before?"
• Mood: chronic pain is a major driver of depression

Frequently Asked Questions

"What are the features of cauda equina syndrome and why is it a surgical emergency?"

Cauda equina syndrome occurs when nerve roots of the cauda equina (below the level of L1/L2) are compressed, most commonly by a large central disc herniation. Key features are: bilateral sciatica, saddle anaesthesia (numbness in the perineum, inner thighs, buttocks, and genitalia), bladder dysfunction (usually urinary retention with overflow incontinence, occasionally urgency or frequency), bowel dysfunction (loss of anal tone, faecal incontinence), and bilateral lower limb weakness. It is a surgical emergency because delayed decompression beyond 48 hours significantly worsens outcomes for continence and motor function. Any suspicion requires emergency MRI spine and same-day surgical review. In an OSCE, always ask about saddle anaesthesia and bladder/bowel symptoms in any back pain history.

"How do you distinguish mechanical back pain from inflammatory back pain on history?"

Mechanical back pain is the most common type and is characterised by: onset often related to activity, lifting, or poor posture; pain that worsens with movement and physical activity; pain that improves with rest; stiffness lasting less than 30 minutes in the morning; age of onset typically 30-60 years; and no systemic features. Inflammatory back pain, most classically seen in ankylosing spondylitis and other seronegative spondyloarthropathies, presents differently: insidious onset before age 40; morning stiffness lasting more than 30 minutes; improvement with exercise and movement rather than rest; pain that is worse at rest and may wake the patient at night in the second half of sleep; associated features including uveitis, psoriasis, and inflammatory bowel disease; and HLA-B27 positivity in over 90% of ankylosing spondylitis cases.

"Which cancers most commonly metastasise to the spine and what features would alert you?"

The cancers most likely to metastasise to the vertebral column are, in order of frequency: breast, prostate, lung, renal cell carcinoma, and thyroid (mnemonic: BLT with Relish and Pickle, or more simply, Breast, Lung, Thyroid, Kidney, Prostate). Features that should alert you to spinal metastasis: age over 50, known history of malignancy, thoracic location (uncommon in mechanical pain), pain that is constant and not relieved by rest or positional change, pain that is worse at night and wakes the patient from sleep, associated systemic features of unexplained weight loss, fatigue, anorexia, or night sweats, and pain that has been progressively worsening over weeks to months without injury. The absence of a prior cancer diagnosis does not exclude metastasis, many patients present with back pain as the first manifestation of an occult malignancy.

"What investigations would you request for a patient with back pain and red flags?"

Initial investigations depend on the suspected cause. For all patients with red flags: FBC (infection or anaemia of malignancy), CRP and ESR (elevated in infection, inflammation, malignancy), calcium (hypercalcaemia in bony metastases or myeloma), LFTs, and PSA in older males (prostate cancer). Urine dipstick (infection or Bence Jones proteins in myeloma). Urgent MRI spine is the investigation of choice for suspected cauda equina syndrome, spinal cord compression, spinal infection (discitis or epidural abscess), or malignancy. Plain X-ray of the spine is useful for fracture and later-stage inflammatory spondylitis (sacroiliitis, bamboo spine) but will miss early changes. CT is useful for bone detail when MRI is unavailable or contraindicated.