Soreness in the middle of the lower back may be caused by physiological reasons such as exercise and fatigue, or it may be caused by pathological reasons such as lumbar disc herniation and rheumatoid arthritis. 1. Physiological reasons: it may be due to the accumulation of lactic acid in the middle of the lumbar region after strenuous exercise, thus the lumbar soreness, which is a normal physiological phenomenon, generally do not need special treatment, and can be relieved after rest. 2. Pathological causes (1) Lumbar intervertebral disc herniation: when the lumbar vertebrae degenerative changes, the intervertebral disc fibrous ring rupture, the nucleus pulposus tissue protrudes in the back or the spinal canal, so that the spinal nerve root suffers from stimulation or compression, which can produce the symptom of soreness in the middle of the posterior lumbar area, and at the same time, there can be radiating pain and numbness in the lower limbs. (2) Rheumatoid arthritis: its occurrence is closely related to group A streptococcal infection, and the specific pathogenesis has not been fully clarified. When rheumatoid arthritis occurs in the lumbar spine, soreness in the lumbar region will occur due to the stimulation of inflammation. Soreness in the middle of the lower back may be caused by other factors, it is recommended that the patient go to the hospital in time, follow the doctor’s instructions for treatment, to avoid delaying the condition.