Sudden intense back pain is commonly caused by a muscle spasm, a strained ligament, or a disc problem after lifting, twisting, or an awkward movement. This kind of pain, while alarming, often improves over days to a few weeks with gentle activity and pain relief.
Less commonly, sudden severe back pain has a serious cause. In older adults or those with weak bones (osteoporosis), it can be a spinal compression fracture, sometimes after minimal force. Rarely, sudden severe back or abdominal pain can be due to a problem with a major blood vessel (such as an aortic aneurysm) or a kidney stone, and back pain with fever can indicate infection.
Seek urgent care or call your local emergency number if sudden severe back pain comes with fainting, a tearing sensation, chest or abdominal pain, breathlessness, numbness in the groin, leg weakness, loss of bladder or bowel control, or fever, or if it follows major trauma. For sudden pain without these features, gentle movement and pain relief usually help, and a doctor can advise if it does not settle.