Sore legs can be caused by strenuous exercise, venous thrombosis, arthritis and so on. 1. Strenuous exercise: After strenuous exercise, such as long-distance running, lactic acid can accumulate in the body, which can cause leg soreness. 2. Venous thrombosis: Deep vein thrombosis confined to the legs can lead to sudden and severe leg pain. Commonly, such as lower extremity venous thrombosis, blood composition, fluidity and other disorders, resulting in hypercoagulable state of the blood, as well as a variety of reasons for prolonged bed rest, resulting in slow blood flow, blood vessel wall damage. 3. Arthritis: When suffering from arthritis, such as arthritis of hip, knee and ankle joints, there will be inflammatory substances oozing out of the joint cavity, and the inflammatory tingling substances will stimulate the muscles and make the leg muscles feel sore. In addition, leg soreness can also be seen in other diseases, if there is no improvement after resting, it is recommended to go to the hospital in time, a clear diagnosis, targeted treatment.