The causes of leg pain are mainly related to vascular lesions in the lower limbs, osteoarthritic diseases, lumbar spine lesions or overwork. 1. Lower limb vascular lesions: If one side of the lower limb has vascular lesions, such as varicose veins or deep vein thrombosis, it will easily affect the local blood circulation, which will lead to the symptom of one leg soreness. 2. Osteoarthritic disease: If there is osteoarthritic disease on one side of the lower limb, such as joint inflammation or degenerative joint disease, it is easy to have the symptom of soreness of one leg. 3. Lumbar spine lesions: when there are changes in the structure of the lumbar spine, such as lumbar disc herniation or lumbar spinal stenosis, etc., it is possible to compress the nerve roots, which may cause abnormal sensory symptoms in one side of the lower limbs, such as one leg soreness. 4. Excessive fatigue: usually, if you carry weight for a long time or exercise strenuously, which leads to excessive fatigue of one leg muscle, it is easy to cause excessive secretion of lactic acid, thus producing the performance of one leg soreness. If the symptoms of a leg soreness is more serious, it is easy to affect the function of the leg, you need to check the cause of the disease, under the guidance of a professional physician targeted treatment, to prevent the symptoms from worsening later.