The left side of the rear waist hurts when pressed, and the common causes are the following: 1. Lumbar muscle strain. Due to prolonged high load activity of the muscles of the lumbar region, or poor recovery after acute injury, coupled with aging and degeneration of the body, resulting in local muscle congestion, edema, inflammatory reaction, will continue to produce pain, and pain will increase when local pressure is applied, and the pain will also increase when moving and standing, and will be relieved when resting. 2, seen in the third lumbar transverse synovial syndrome The third lumbar vertebra is longer, and is the source of much of the pain. The third lumbar vertebra is relatively long and is the stopping point of many muscles and ligaments, which can easily lead to aseptic inflammation of the stopping point of the ligaments and tendons of the third lumbar vertebra after high load activities lead to strain, resulting in pressure pain on one side. 3. The pain is also aggravated by the increased pressure when pressing.