Soreness in the upper left leg may be caused by physiological factors such as overexertion, or it may be caused by trauma, lumbar spondylosis, vascular factors and other pathological reasons. 1. Physiological factors: due to prolonged heavy physical labor or exercise, the leg muscles are overworked, local lactic acid and other metabolic products accumulate, resulting in soreness of the leg muscles, which can be relieved by reducing activities and resting more. 2. Trauma: Violence or fall and other factors can cause local muscle or ligament tissue injury, resulting in subcutaneous bruising, swelling and pain in the soft tissues of the leg muscles, and in severe cases, fracture may also occur, such as femur fracture, etc., which requires timely hospital examination and treatment. 3. Lumbar spine lesions: If there are lumbar spine lesions, such as lumbar spondylolisthesis, lumbar disc herniation, lumbar spinal stenosis, intradural tumors, etc., which will lead to narrowing of the spinal nerve root space, and if the left side of the spinal cord nerve root is compressed, it will lead to soreness and pain in the upper part of the left leg. 4. Vascular factors: If there are vascular factors such as narrowing of the left lower limb artery, resulting in blood supply obstacles, ischemic pain in the upper left leg, or due to deep vein thrombosis or varicose saphenous vein in the upper left leg, it will cause the venous blood return is not good, and the symptoms of soreness in the lower limbs. Soreness in the upper left leg may be caused by other reasons, and it is recommended that the patient consult a doctor in time to improve the examination and carry out targeted treatment.