Lumbar Strain

Acute injury to the paraspinal muscles, fascia and ligaments of the lower back from lifting, twisting, sudden movement, or overuse, with no radiculopathy or serious cause. It is the commonest cause of acute low back pain and the commonest reason for work absence in adults aged 20 to 50 years.

• About 60 to 80% of adults have an episode of low back pain in their lifetime. Most (about 90%) are non-specific or mechanical, and strain is the main cause.
• Risk factors: heavy manual work, repetitive bending and lifting, prolonged sitting, obesity, smoking, poor core strength and fitness, previous low back pain, psychosocial stress and job dissatisfaction, and pregnancy.
• Natural history: about 80 to 90% recover within 6 weeks, with the greatest improvement in the first 2 weeks. Recurrence in 1 year is about 25 to 60%, and about 10% progress to chronic pain.

• Sudden or gradual onset of dull, aching or sharp pain in the low back, sometimes with referred pain to the buttock or posterior thigh (not below the knee), with muscle spasm, stiffness, and pain on bending, twisting, coughing or sitting. Pain eases on lying with knees flexed.
• Examination: tender paraspinal muscles, reduced lumbar range, antalgic posture or scoliosis, and normal neurological findings (power, sensation, reflexes, straight leg raise negative for radicular pain).
• Red flags for serious pathology:
  • Cauda equina syndrome: urinary retention or incontinence, faecal incontinence, saddle numbness, bilateral leg weakness or sciatica (emergency).
  • Fracture: major trauma, age above 70, osteoporosis, long term corticosteroid use.
  • Malignancy: history of cancer, unexplained weight loss, age above 50 with new pain, constant night pain.
  • Infection: fever, immunosuppression, injection drug use, recent surgery or infection.
  • Inflammatory back pain (spondyloarthritis): onset below 40 years, insidious, morning stiffness above 30 minutes, improves with exercise, not with rest, night pain in the second half.
  • Aortic aneurysm: abdominal pulsatile mass, vascular risk, severe pain with hypotension.
  • Progressive neurological deficit.
• Differential diagnosis: lumbar disc herniation with radiculopathy, spinal stenosis, facet joint arthropathy, sacroiliac joint dysfunction, spondylolysis and spondylolisthesis, vertebral compression fracture, spondyloarthritis, infection (discitis, osteomyelitis, epidural abscess), malignancy and metastasis, aortic aneurysm, renal colic, pyelonephritis, pancreatitis, and gynaecological causes.
• Complications: chronic low back pain, recurrent episodes, work disability, depression and opioid dependence.

• Clinical, with screening for red flags and psychosocial risk factors (yellow flags: fear avoidance, catastrophising, depression, job dissatisfaction, compensation issues).
• No imaging is needed for acute non-specific low back pain without red flags, because findings correlate poorly with symptoms and imaging leads to unnecessary interventions. Imaging is considered for red flags, progressive neurological deficit, suspected cauda equina (emergency MRI), pain persisting beyond 6 weeks with failure of treatment, or when surgery or injection is contemplated.
• X-ray for suspected fracture or in older patients with trauma. MRI is the best test for neurological compromise, infection, tumour and disc disease.
• Blood tests (full blood count, CRP, ESR, calcium, alkaline phosphatase, and prostate specific antigen or myeloma screen where relevant) when infection, inflammatory disease or malignancy is suspected. Urinalysis if renal pathology is possible.

• Reassurance and advice to stay active: continue normal activities as pain allows, return to work early with modified duties, and avoid bed rest (more than 1 to 2 days delays recovery).
• Heat: a heat wrap or hot water bottle for 15 to 20 minutes, several times a day, gives short term relief.
• Analgesia (the aim is to keep movement, not to abolish pain):
  • Paracetamol has little proven benefit for acute low back pain on its own, but is safe and may be used 1 g orally 6 hourly (maximum 4 g per day).
  • NSAIDs are the most effective first line drugs: ibuprofen 400 mg orally 8 hourly with food, naproxen 500 mg 12 hourly, or diclofenac 50 mg 8 hourly, for 5 to 10 days at the lowest effective dose, with a proton pump inhibitor (omeprazole 20 mg daily) in at risk patients. Avoid in renal impairment, heart failure, peptic ulcer and from 20 weeks of pregnancy. Topical diclofenac 1% gel 2 to 4 g 3 to 4 times daily is an alternative. Etoricoxib 60 to 90 mg daily is used in patients with gastrointestinal risk and no cardiovascular risk.
  • Muscle relaxants for short periods (up to 5 to 7 days) in severe spasm: tizanidine 2 mg at night increasing to 2 to 4 mg 8 hourly (maximum 36 mg per day, monitor liver function), cyclobenzaprine 5 to 10 mg at night, methocarbamol 1.5 g orally 4 times daily for 2 to 3 days then 1 g 4 times daily, or orphenadrine 100 mg orally 12 hourly. Warn about drowsiness and avoid driving. Diazepam 2 to 5 mg at night for 3 days is an alternative but has a dependence risk.
  • Opioids are not routinely recommended. If pain is severe and not controlled by other measures, give the lowest dose for the shortest time (codeine 30 mg with paracetamol 500 mg to 1 g, up to 3 days, or tramadol 50 mg 6 to 8 hourly for up to 3 to 5 days).
  • Oral corticosteroids, gabapentinoids and antidepressants have no benefit for acute non-radicular back pain.
• Exercise and physiotherapy: start once pain allows (often within 1 to 2 weeks): walking, graded core and trunk stabilisation, hip mobility, and extension and flexion exercises. A structured programme for subacute pain (over 4 to 6 weeks) or recurrent pain. Manual therapy (spinal manipulation, mobilisation) gives modest short term relief.
• Education on lifting technique (bend knees, keep the load close, avoid twisting), ergonomic adjustments, weight loss, smoking cessation, and regular exercise to reduce recurrence.
• Chronic low back pain (over 12 weeks): active rehabilitation, cognitive behavioural therapy, exercise therapy, duloxetine 30 to 60 mg daily, a short trial of tricyclic antidepressant at low dose, and a multidisciplinary approach. Invasive treatment is considered for selected patients.
• Cauda equina syndrome: emergency MRI and surgical decompression.
• Special groups:
  • Pregnancy: paracetamol, heat, exercise, a support belt and physiotherapy. Avoid NSAIDs after 20 weeks, and avoid muscle relaxants.
  • Elderly: higher risk of fracture and malignancy, avoid sedating muscle relaxants and NSAIDs in renal impairment, and assess falls.
  • Adolescents: consider spondylolysis, scoliosis and infection.
  • Anticoagulation: avoid NSAIDs, and use paracetamol and topical agents.
  • Renal and hepatic impairment: avoid NSAIDs and adjust tizanidine.
• Follow up: review at 2 weeks if not improving, and at 6 weeks. Refer to physiotherapy, spinal services or pain clinics for failure beyond 6 weeks, recurrent disabling episodes, red flags, or neurological findings.