Soreness in the left leg may be related to physiological factors such as overwork and damage to muscle tissues, as well as pathological factors such as calcium deficiency, lumbar disc herniation, rheumatoid arthritis, arteritis and varicose veins. 1. Physiological factors (1) Fatigue: If heavy physical labor is performed or the labor is too long, resulting in excessive accumulation of local lactic acid, it will make the left leg sore, and proper rest is needed to relieve it. (2) Muscle tissue damage: If the muscle tissue is damaged during exercise, soreness will also occur. This is a normal stress manifestation of the human body. 2. Pathological factors (1) Calcium deficiency: when the patient is deficient in calcium and the blood calcium decreases, the calcium intake in the bones will be insufficient, and the lack of calcium in the bones may trigger symptoms such as leg pain and weakness. (2) Lumbar intervertebral disc herniation: mainly caused by disc degeneration, injury, abnormal development of lumbar vertebrae, etc. It often shows lumbar pain, radiating pain in the lower limbs, numbness, weakness, etc., which may lead to the appearance of left leg pain. (3) Rheumatoid arthritis: mainly caused by autoimmunity and heredity, it often shows stiffness, swelling and pain in the joints, which may lead to left leg pain. (4) Arteritis: Arteritis of the left leg may cause clinical symptoms of left leg pain because of insufficient blood supply to the left leg. (5) Varicose veins: Varicose veins in the left lower extremity can cause swelling and soreness in the left leg due to impaired blood circulation. Therefore, if you have left leg pain, if it does not get better or worsens significantly, it is recommended to consult a doctor as soon as possible to find out the cause.