This term refers to a condition when the vertebrae due to various causes, are unable to withstand physiological loads. This causes increased movement between the vertebrae. As a result, the spine starts moving in a particular pattern. This also leads to pinching and irritation of nerve roots. Medical conditions like spondylolisthesis, fractures, scoliosis, spinal infection or tumour and degenerative disc disease result in disc instability. Symptoms include significant back pain, sudden stabbing pain, spasm and locking up of the back. Diagnosis after physical exam is confirmed using imaging tests.

If conservative treatment does not help as in many cases, the condition is best treated by spinal fusion surgery. Basically the vertabrae bones which move abnormally are fused together. A brace may have to worn to ensure additional stability. Patient can start walking immediately after surgery and there is no need for prolonged bed rest as often thought. Physical therapy has to be undergone to improve flexibility and strength of spine.