Chronic pain
Exam Tips
- In OSCEs, define chronic pain as >3 months and immediately frame assessment as biopsychosocial plus red-flag exclusion.
- Differentiate chronic primary pain (distress/disability not better explained by another diagnosis) from chronic secondary pain (clear underlying condition).
- State that routine long-term opioids are not recommended for chronic primary pain; discuss dependence and overdose risk explicitly.
- Score highly by setting function-based goals (sleep, walking distance, return to work) rather than pain-score-only goals.
- Always screen for depression, anxiety, sleep problems, and medicine misuse; these strongly influence prognosis and treatment response.
Definition
Chronic pain is pain that persists or recurs for longer than 3 months and is an unpleasant sensory and emotional experience linked to actual or potential tissue damage, or resembling it. In UK practice it is assessed using a biopsychosocial model, and may be chronic primary pain (where distress/disability is prominent and not better explained by another diagnosis), chronic secondary pain, or both.
Pathophysiology
Chronic pain reflects peripheral and central sensitisation rather than only ongoing tissue injury. Repeated nociceptive input (for example from osteoarthritis or spinal disorders) can increase dorsal horn excitability, reduce descending inhibitory control (serotonergic/noradrenergic pathways), and promote maladaptive cortical-emotional processing (catastrophising, anxiety, poor sleep), producing persistent pain, hyperalgesia, fatigue, and functional decline. This aligns with nociceptive, neuropathic, and nociplastic mechanisms that frequently overlap in the same patient. See Figure: descending pain modulation and central sensitisation in standard pain-physiology textbook diagrams.
Risk Factors
- Female sex
- Age over 45 years
- Socioeconomic deprivation and unemployment
- Occupations with prolonged standing/repetitive low-level movement or heavy manual work
- Physical inactivity
- Smoking and excess alcohol use
- Obesity
- Multimorbidity
- Psychological distress (anxiety, depression), pain catastrophising, maladaptive coping
- Sleep disturbance
- History of trauma, surgery, or prior chronic pain
- Family history of pain syndromes (for example migraine, fibromyalgia)
- Pregnancy (higher musculoskeletal/neuropathic pain risk)
Clinical Features
Symptoms
- Pain lasting more than 3 months, persistent or fluctuating
- Pain at one site, regional, or widespread (for chronic widespread pain: multiple body regions)
- Disproportionate pain severity relative to identifiable tissue pathology in chronic primary pain
- Functional impairment (reduced mobility, sleep disturbance, difficulty with work/self-care/social participation)
- Emotional distress (low mood, anxiety, frustration, anger)
- Neuropathic descriptors in some patients (burning, shooting, electric-shock pain, allodynia)
Signs
- Variable tenderness and reduced range of movement at affected sites
- Deconditioning (reduced strength/endurance, guarded movement)
- Allodynia or hyperalgesia on sensory examination
- In CRPS: oedema, temperature/colour asymmetry, sweating change, trophic skin/nail change, motor dysfunction
- Usually no focal neurological deficit unless a secondary structural/neurological cause is present
- Possible mood or affective changes on consultation
Investigations
Management
Lifestyle Modifications
- Use a person-centred, shared decision-making plan with clear functional goals
- Promote graded physical activity/exercise programmes (aerobic, strengthening, pacing) as first-line
- Support sleep hygiene, stress reduction, and psychological therapies (for example CBT/ACT-based pain programmes)
- Address smoking, alcohol, weight, occupational ergonomics, and social determinants
- Consider multidisciplinary pain rehabilitation and occupational therapy for persistent disability
Pharmacological Treatment
Antidepressants for chronic primary pain (NICE-supported option in adults)
- Amitriptyline 10 mg at night initially, titrate gradually (commonly to 25-75 mg at night depending on response/tolerability)
- Duloxetine 30 mg once daily initially, increase to 60 mg once daily after 1 week if needed/tolerated
- Sertraline 50 mg once daily (if selected after shared decision-making, particularly with comorbid depression/anxiety)
Use mainly to improve quality of life, sleep, and function; review benefit/harms regularly. Cautions: anticholinergic effects and QT risk with tricyclics; serotonin syndrome risk with serotonergic combinations; duloxetine avoid in severe hepatic impairment and use caution in uncontrolled hypertension.
Simple analgesia/NSAIDs for chronic secondary musculoskeletal pain (condition-specific use)
- Paracetamol 1 g up to four times daily (max 4 g/day in adults)
- Ibuprofen 400 mg three times daily with food (max 2.4 g/day)
- Naproxen 250-500 mg twice daily
Use lowest effective dose for shortest duration; co-prescribe gastroprotection (for example omeprazole 20 mg once daily) when GI risk is present. Contraindications/warnings for NSAIDs: active peptic ulcer, significant renal impairment, severe heart failure, and caution with anticoagulants/CVD risk.
Opioids and other medicines generally not initiated for chronic primary pain in non-specialist care
- Codeine 30-60 mg every 4-6 hours (max 240 mg/day) - avoid routine long-term use
- Tramadol 50-100 mg every 4-6 hours (max 400 mg/day) - avoid routine long-term use
For chronic primary pain, do not initiate opioids, benzodiazepines, antiepileptics (gabapentin/pregabalin), antipsychotics, corticosteroids, ketamine, or local anaesthetics outside specialist indications because long-term benefit is limited and harm (dependence, falls, cognitive effects, overdose, endocrine and bowel adverse effects) is significant.
Surgical / Interventional
- No surgery for chronic primary pain itself
- Offer procedure only for an identified treatable secondary cause (for example joint replacement for severe osteoarthritis, decompression for selected nerve/root compression) after specialist assessment
Complications
- Physical disability and deconditioning
- Depression and anxiety (high comorbidity burden)
- Sleep disturbance and fatigue
- Medicine adverse effects (for example NSAID GI/renal/cardiovascular toxicity; opioid-related constipation, dependence, overdose)
- Problematic opioid or sedative use
- Reduced quality of life, social isolation, work loss, and financial impact
Prognosis
Course is often prolonged (months to years) with stable or fluctuating trajectories; complete remission is uncommon in many syndromes, but clinically meaningful improvement in pain impact and function is achievable, especially in the first 3-6 months of active multidisciplinary management. Worse outcomes are linked to severe baseline pain/disability, widespread pain, long symptom duration, depression/anxiety, poor sleep, catastrophising, multiple comorbidities, and weak social support.
Sources & References
🏥BMJ Best Practice(4)
💊BNF Drug References(2)
- Dihydrocodeine tartrate[management.pharmacological]
- Morphine[management.pharmacological]
✅NICE Guidelines(1)
- Chronic pain[overview]
📖Textbook References(6)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1725)[context]
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 609)[context]
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 610)[context]
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 609)[context]
- Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 609)[context]
- [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 262, 263)[context]