The causes of left leg soreness and weakness include excessive exercise, lumbar disc herniation, deep vein thrombosis, etc. General treatment, medication and surgery should be chosen according to the causes. 1. Excessive exercise: For the left leg soreness and weakness caused by excessive exercise and large accumulation of lactic acid, it can be effectively relieved after a period of time by resting and massaging the leg. 2. Herniated lumbar disc: For herniated lumbar disc caused by compression of nerve root, rest should be paid attention to, and oral ibuprofen and other non-steroidal anti-inflammatory drugs can be taken as prescribed by the doctor; if the conservative treatment is ineffective, lumbar spine surgery can be chosen. 3. Deep vein thrombosis of the left lower limb: it is one of the most common causes of lower limb pain, which requires bed rest, elevation of the affected limb, and oral rivaroxaban, sodium heptaphylloside and other medications; for those who are in serious condition or those who are ineffective in conservative treatments, they can choose surgical treatments. Soreness and weakness of the left leg may have other causes, if the symptoms are not relieved, it is recommended to consult a doctor to clarify the cause of the disease and standardize the treatment under the guidance of the doctor.