Stiffness of the back after squatting and standing may be caused by ankylosing spondylitis, lumbar disc herniation, muscle strain and other reasons. 1. Ankylosing spondylitis: it is a chronic progressive inflammation of the spine, which is mainly caused by heredity and infection. Due to the stimulation of inflammation, patients may have lower back pain, and feel stiffness in the lower back when they get up in the morning or sit for a long time. 2. Lumbar intervertebral disc herniation: mainly due to various causes of lumbar vertebrae with different degrees of degenerative changes, the nucleus pulposus protrudes, leading to the adjacent spinal nerve roots suffer from irritation or compression, resulting in lumbar pain. Patients can appear lumbar activity limitation, stiffness, numbness and other feelings, which can cause squatting and standing after the phenomenon of lumbar stiffness. 3. Muscle strain: such as ligaments around the lumbar spine, muscle long-term incorrect living and working habits of strain, can lead to pain, soreness and muscle stiffness, accompanied by lumbar mobility decline in symptoms, that is, squatting and standing after the phenomenon of lumbar stiffness. There may be other reasons, it is recommended that patients with squatting back stiffness go to the hospital in a timely manner, in accordance with the doctor’s instructions for treatment, to avoid delaying the condition.