There are many causes of lumbar stiffness, such as muscle strain, intervertebral disc herniation, lumbar sprain and so on. 1. Muscle strain: due to muscle strain damage in the lumbar region, local swelling, edema, pathological changes in the lumbar fascia, tissues, etc., which may cause lumbar stiffness. 2. Intervertebral disc herniation: degenerative lesions of lumbar intervertebral discs, due to the herniation of the nucleus pulposus, resulting in the dura mater and nerve roots being squeezed, and the lumbar muscles being tense and spasmodic, leading to lumbar muscle stiffness. 3. Lumbar sprain: lumbar sprain, damage to the lumbar muscles, lumbar soft tissue edema, oozing, etc., which can be clinically manifested as lumbar stiffness. There are many reasons for the hardening of the waist, you need to go to the hospital for specialist examination, under the guidance of the physician symptomatic treatment, to avoid further aggravation of the condition.