Soreness on one side of the waist may be related to lumbar muscle strain, unilateral kidney disease, gynecological disease and so on. 1. Lumbar muscle strain: commonly found in long-term heavy manual laborers, may habitually one side of the waist to exert force, frequent lumbar activities, long-term in the state of strain, thus appearing lumbar muscle soreness. 2. Unilateral kidney diseases: for example, hydronephrosis, which may be caused by stones blocking the junction of ureter and renal pelvis, resulting in urine retention, which cannot be discharged smoothly, and hydronephrosis, which may also cause unilateral lumbar soreness and swelling. 3. Gynecological diseases: for example, unilateral inflammation of the fallopian tube, usually accompanied by uterine inflammation, through the endometrium of the uterus upward spread to the fallopian tube, causing the mucous membrane of the fallopian tube is swollen, appearing in one side of the waist soreness and distension of the situation. Soreness on one side of the waist can also be seen in other causes, it is recommended to consult a doctor in a timely manner, follow the doctor’s instructions to carry out relevant examinations, with the help of the doctor to clarify the causes, and targeted treatment or therapy.