The phenomenon of knee pain in the middle of pregnancy is more common, and its causes are mainly the following: First, the patient is deficient in certain trace elements such as calcium, the lack of calcium is likely to lead to the lack of stability of bone tissue, which leads to the phenomenon of pain. Second, endocrine disorders, easily lead to the ligaments and tendons at the knee become relaxed, the ability to protect the joints is reduced, thus causing pain. Third, the fetus in the middle of pregnancy has grown larger and will have a certain weight, which will lead to increased pressure on the knee joint, and the ligaments will have a certain strain, resulting in pain. During this period, patients should pay more attention to rest, regularize their work and rest time, avoid staying up late and get enough sleep. Eat a diet rich in calcium to replenish the nutrients and vitamins needed by the body. Pay attention to the warmth of the knee, avoid getting cold, and do not stand for a long time during pregnancy, which will help to relieve the knee pain.