This term refers to a condition when the vertebrae due degeneration, 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 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. The condition is best treated by spinal fusion surgery performed with anterior, posterior or combined approach. Three months are required for the bones to fuse together. A brace may have to worn to ensure stability. Physical therapy has to be undergone to improve flexibility and strength of spine.