Back pain refers to pain arising from the spine or surrounding muscles, ligaments, joints and other tissues, and it can occur anywhere from the upper back to the lower back. Most back pain is nonspecific, meaning no single anatomical structure can be identified with certainty as the sole pain generator. Common contributors include muscle or ligament strain, altered loading, spinal joint irritation, disc-related disorders and age-related changes.
More specific causes include vertebral fracture, infection, inflammatory spinal disease, malignancy and nerve-root compression. Back pain can be acute, subacute or chronic, and pain intensity does not necessarily indicate the seriousness of the underlying condition. Many episodes improve with time and appropriate activity, but persistent, recurrent or severe symptoms may require assessment.
Mechanical or nonspecific back pain is the most common category. It can arise after lifting, awkward movement, prolonged static posture, increased physical workload or sometimes without a clear precipitating event. Muscles, tendons, ligaments, facet joints, intervertebral discs and other tissues can contribute, but conventional imaging often cannot identify which structure is responsible. Muscle spasm may occur as part of the body's response to pain but is not necessarily the original cause. Factors such as physical deconditioning, sudden changes in activity, occupational demands, sleep problems, stress and previous episodes can influence the persistence of symptoms. The term "mechanical" describes a relationship with movement or loading rather than proving a specific damaged structure.
Intervertebral discs can contribute to back pain through degeneration, annular injury or herniation. Discs consist of a gelatinous nucleus pulposus surrounded by a fibrous annulus and positioned between vertebral bodies. Degenerative disc changes become increasingly common with age and can be present without symptoms, so disc abnormalities on MRI are not automatically evidence of the cause of pain.
A disc herniation can irritate or compress a nearby nerve root, producing radicular pain that may travel into the buttock or leg and may be accompanied by numbness, tingling or weakness. This is commonly called sciatica when the symptoms follow the sciatic distribution, although sciatica is a symptom pattern rather than a specific disease.
Facet joints, sacroiliac structures and spinal muscles can also contribute to pain. Facet joints are synovial joints between adjacent vertebrae and can develop osteoarthritic changes. Their degeneration may coexist with disc degeneration and does not necessarily identify the precise source of pain. The sacroiliac joints connect the sacrum with the pelvis and can produce buttock-region pain in some people, although diagnosis can be challenging. Muscles and connective tissues surrounding the spine provide stability and movement and can become painful following overloading or injury. Because several structures can be affected simultaneously, back pain is often better understood as a multifactorial condition than as one isolated lesion.
Inflammatory conditions can cause characteristic back pain. Axial spondyloarthritis is an inflammatory rheumatic disease affecting the sacroiliac joints and spine and often begins in younger adulthood. Its pain may improve with exercise, worsen with prolonged rest, cause significant morning stiffness and disturb sleep, particularly during the second half of the night. This contrasts with many mechanical pain patterns, although symptoms can overlap. Other inflammatory diseases and infections can also affect the spine. Persistent inflammatory features, especially in a younger person with associated psoriasis, inflammatory bowel disease, uveitis or a relevant family history, can warrant specialist assessment.
Serious but less common causes include vertebral fracture, spinal infection and cancer. Fracture risk increases with osteoporosis, older age and certain medications or medical conditions, and fractures can occur after relatively minor trauma in vulnerable individuals. Spinal infection can produce severe pain, fever or systemic illness, although fever is not always present. Malignancy involving the spine may cause persistent or progressive pain and can sometimes produce neurological compromise. Red flags such as major trauma, known cancer, significant immune suppression, unexplained weight loss, fever, progressive neurological deficits or new bladder or bowel dysfunction change the urgency and scope of assessment.
Psychological and social factors can influence the experience and persistence of back pain without implying that the pain is imaginary or purely psychological. Stress, fear of movement, depression, anxiety, poor sleep and occupational or social difficulties can interact with biological factors and affect pain sensitivity, activity and recovery. Chronic pain can produce changes in the nervous system's processing of sensory signals, sometimes described as nociplastic mechanisms. These mechanisms can coexist with structural pathology. Consequently, chronic back pain is often best approached using a biopsychosocial framework that considers tissue health, nervous-system processing, physical activity, sleep, mood and social context rather than assuming a single anatomical lesion explains every symptom.
Assessment begins with history and examination and does not automatically require imaging. Imaging is generally more useful when serious pathology is suspected, neurological deficits are present, symptoms persist despite appropriate management, or a specific structural diagnosis would alter treatment. MRI is particularly useful for evaluating nerves, discs, spinal cord and certain infections or tumours, whereas X-rays are useful for fractures and some structural changes.
Management commonly involves remaining appropriately active, exercise and rehabilitation, education, and selected medicines according to the cause and individual circumstances. Urgent medical assessment is required for new severe neurological deficits, saddle-area numbness, new loss of bladder or bowel control, suspected spinal infection or fracture, or other symptoms suggesting serious disease.
