Legs have no strength and weakness, may be caused by strenuous exercise, may also be and lower extremity venous thrombosis, cerebrovascular disease and other related. 1. Strenuous exercise: daily if the amount of exercise is relatively large, after exercise, if there is no stretching exercise, no massage of the leg muscles, may lead to the legs appear soft and weak situation. 2. Lower extremity venous thrombosis: Lower extremity venous thrombosis is the coagulation of blood in the deep venous system of the lower extremities. Lower extremity venous thrombosis will cause bruising of the lower extremities, and the patient will show swelling of the lower extremities and weakness of the legs. 3. Cerebrovascular disease: cerebrovascular disease can cause patients to have weak and achy legs, common diseases include cerebral hemorrhage, cerebral infarction, etc., which often occur in middle-aged and old people. Legs have no strength and weakness, need to go to the hospital in time, patients should not blindly treatment.