Common causes of sudden leg soreness include too much exercise, herniated lumbar disc, osteoarthritis of the knee, and cold legs. 1. Excessive exercise: this can lead to increased muscle oxygen consumption and insufficient oxygen uptake, resulting in a large amount of lactic acid production, and the accumulation of lactic acid will produce a feeling of soreness. 2. Lumbar disc herniation: because the herniated nucleus pulposus compresses the nerve root, causing radiating pain in the lower limbs, which can also turn into soreness. 3. Osteoarthritis of the knee joint: it is a degenerative change that occurs in the knee joint, which can be accompanied by bone destruction, synovial inflammation, etc., and can also cause soreness in the lower limbs. 4. Cold legs: causes vascular contraction in the lower limbs, which leads to ischemia and hypoxia in local tissues, resulting in soreness and pain. The causes of sudden leg soreness are more varied, and may also be related to vascular diseases, gout, tumors and other diseases. If the symptoms continue to be unrelieved, it is recommended to consult a doctor in time to clarify the cause of the disease and carry out targeted treatment.