There are many reasons why the joints of the back are crunchy while sleeping, such as cold back, back strain, thoracolumbar disc herniation, spondylitis, and so on. 1. Cold back: If the back suffers from cold stimulation, it will lead to vasoconstriction of the blood vessels in the back, muscle spasm, blood circulation is reduced, and can not provide sufficient nutrition for the muscles and joints, which will lead to the back joints appearing crispy during sleep. 2. Back muscle strain: long-term use of the back to carry out weight-bearing exercise or stooping activities will lead to chronic injury to the lumbar muscles, resulting in oozing, edema and other aseptic inflammation, which in turn affects the joints of the back, so that when you sleep, there is a feeling of numbness in the back. 3. Herniated thoracolumbar intervertebral discs: long-term incorrect posture or stooping will lead to degenerative changes in the thoracolumbar intervertebral discs, the physiological curvature of the thoracolumbar vertebrae is abnormal, which will lead to the discomfort of the back joints when sleeping. 4. Spondylitis: Inflammation of the spinal cord and surrounding tissues may affect the intercostal nerves, causing pain and numbness in the joints of the back due to compression of the intercostal nerves. If the back joints appear obvious tingling sensation when sleeping, it is recommended to immediately go to the orthopedic department of the hospital for consultation and examination and targeted treatment.