Back Pain: Most Common Cause, Red Flags & Recovery Tips

Common Causes

References

Sources cited on this page. PubMed links open the original abstract.

1. Walker BF. The prevalence of low back pain: a systematic review of the literature from 1966 to 1998. J Spinal Disord. 2000;13(3):205–217. PMID 10872758 · doi:10.1097/00002517-200006000-00003
2. Maher C, Underwood M, Buchbinder R. Non-specific low back pain. Lancet. 2017;389(10070):736–747. PMID 27745712 · doi:10.1016/S0140-6736(16)30970-9
3. Qaseem A, Wilt TJ, McLean RM, Forciea MA. Noninvasive Treatments for Acute, Subacute, and Chronic Low Back Pain: A Clinical Practice Guideline From the American College of Physicians. Ann Intern Med. 2017;166(7):514–530. PMID 28192789 · doi:10.7326/M16-2367

Red flag symptoms that need urgent investigation

The vast majority of back pain is mechanical, caused by muscle strain, disc irritation, or postural stress, and resolves with analgesia and physiotherapy.² But a small proportion signals something serious. UK NICE guidance (NG59) identifies the following "red flags" that warrant urgent investigation:

• Cauda equina syndrome: New onset of bladder or bowel dysfunction (inability to pass urine, incontinence, or reduced urinary sensation), saddle anaesthesia (numbness around the inner thighs and buttocks), or bilateral leg weakness. This is a surgical emergency, delay risks permanent paralysis.
• Cancer: Back pain in someone with a personal history of cancer (especially breast, prostate, kidney, lung, thyroid, all common sites for spinal metastases), unexplained weight loss, or pain that is worse at night or at rest (mechanical pain typically improves with rest).
• Infection (discitis / vertebral osteomyelitis): Back pain with fever, recent urinary tract or skin infection, intravenous drug use, or immunosuppression. ESR and CRP are the most sensitive initial blood tests.
• Fracture: Sudden severe back pain after minimal trauma in an older adult or a patient on long-term steroids, suspect osteoporotic vertebral fracture.
• Inflammatory back pain (axial spondyloarthritis / ankylosing spondylitis): Onset before age 45, morning stiffness lasting more than 30 minutes, improves with exercise, associated with iritis or psoriasis. CRP, HLA-B27 antigen, and MRI sacroiliac joints are key investigations.

Blood tests used in back pain investigation

For uncomplicated mechanical back pain, no blood tests are routinely needed. Blood tests are ordered when red flags are present or when the pain is not improving as expected:

• FBC: Anaemia plus back pain can indicate multiple myeloma (a cancer of plasma cells in bone marrow) or metastatic disease. A raised white count suggests infection.
• ESR and CRP: Elevated in infection, inflammation, and cancer. An ESR above 50 mm/hr in an older patient with new back pain warrants prostate-specific antigen (PSA) in men and whole-spine MRI regardless of gender.
• Protein electrophoresis and serum-free light chains: The primary screening tests for multiple myeloma, looking for an abnormal paraprotein band.
• PSA (prostate-specific antigen): In men over 50 with back pain, a raised PSA can identify prostate cancer with spinal metastases.
• Calcium: Hypercalcaemia can cause bone pain; it occurs in primary hyperparathyroidism and malignancy (especially myeloma and bone metastases).
• HLA-B27: Present in 90% of people with ankylosing spondylitis, though it is also found in 8% of the general population, use in combination with clinical features, not in isolation.

Scans and when they add value

For mechanical back pain without red flags, X-ray and MRI are not routinely recommended in the first 6 weeks, they rarely change management and often reveal age-related "incidental" findings that can falsely alarm patients. MRI is the investigation of choice when cauda equina syndrome, infection, malignancy, or inflammatory disease is suspected, or if conservative treatment has failed after 6 weeks.