The symptoms of weak legs after coitus are mainly caused by improper movements during coitus, or too strenuous movements during coitus, or keeping the same position for a long time. If the posture is not correct or keep the same position for too long, coupled with the coital activities are very violent, may affect the blood flow of the legs, the blood supply of the legs if insufficient, there will be a distal nutritional deficit, so a large number of lactic acid buildup, there will be the symptoms of leg weakness and acidity. Therefore, when having intercourse, pay attention to the combination of work and rest, pay attention to the correctness of the posture, and do not keep the same position for too long in the same room, so that the damage to the body is very big. Other reasons, from the perspective of traditional Chinese medicine, may be due to heavy damage to kidney qi leading to lumbar and knee weakness, which can be treated by using drugs to tonify the kidneys and strengthen the bones. If there is no relief within a short period of time, you must go to a regular hospital in time.