What is the reason for one side waist pain

Unilateral low back pain, consider the following reasons: first, the most common is lumbar muscle strain, more common in young adults, because of long-term sitting, standing and incorrect posture under the work or labor caused by chronic lumbar muscle strain, causing pain; second, side low back pain can also be seen in urinary stones, it is more intense pain, restlessness, but also may be accompanied by fever or urine blood; third, side low back pain may be caused by lumbar arthritis. These are three more common and relatively mild diseases. If we want to find out the real cause of this back pain, there are some more complex and relatively rare diseases, which need to be further examined in the hospital.