Sudden bending flash waist, the common causes are as follows: First, muscle strain: sudden bending can lead to acute strain of the lumbar muscles, the patient will have the feeling of flash waist, at the same time, there will be lumbar pain, lumbar spine activities are limited, generally rest for a few days, that is, you can make the clinical symptoms to get complete relief. Second, joint dislocation: sudden bending can make the lumbar spine small joints transient dislocation, lumbar spine small joints in a short period of time after the rapid self-replacement. If there is no self-replacement, the pain symptoms will be extremely severe. This usually indicates that the patient has a long-term lumbar joint disorder, and a CT scan of the lumbar spine can confirm the diagnosis. Early bed rest and lumbar spine manipulation can relieve the clinical symptoms. Therefore, the sudden bending of the waist flash symptoms should be diagnosed and treated in a timely manner.