The two main reasons for the swelling and pain on both sides of the back are the following two: 1. Due to overworking of the muscles and soft tissues such as ligaments at the sacroiliac joints of the back, strain will occur, which will produce more lactic acid and metabolites such as inflammation locally, which will stimulate the peripheral nerves around the area, and the feeling of swelling and pain will occur. 2. Due to the cold in the lumbosacral area, the muscles and ligaments become more tense and fatigued. Blood circulation will also slow down, and metabolites will gradually increase, which also tends to aggravate the feeling of distension and pain. Therefore, after this situation, you need to keep the lumbar area relaxed, try to place soft pillows behind the thighs on both sides when lying down, and keep the knee and hip joints flexed, so that the muscles and ligaments of the lumbar area can be in a relaxed state. You can also pay attention to the warmth of the lumbar and lumbosacral area, not to be cold, you can use a warm water bag hot compress, you can also apply the blood circulation, swelling and pain relief cream, can effectively relieve the symptoms.