The causes of sudden leg pain include lumbar disc herniation, osteomyelitis, leg trauma, skin infection, muscle strain and so on. 1. Herniated lumbar intervertebral discs: Herniated lumbar intervertebral discs can cause lumbar and leg pain by stimulating the sciatic nerve when bending or exercising, which can be relieved when resting if the symptoms are not serious. 2. Osteomyelitis: Osteomyelitis of femur or tibial fibula caused by purulent bacteria can lead to local pain, pressure pain and generalized fever and other symptoms. 3. Leg trauma: When walking in the jungle or other complex environments, one may inadvertently cut the leg with grass or cut the leg with steel wire, thus causing leg pain. 4. Skin infections: Mosquito bites on the skin of the legs can cause a localized inflammatory reaction leading to localized pain. 5. Muscle strain: improper or excessive exercise can strain the leg muscles, resulting in leg pain. Sudden leg pain may also have other pathologic factors, such as lower extremity vascular disease, etc., it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.