Soreness and weakness of both legs may be caused by over-fatigue, calcium deficiency, lumbar disc herniation, chronic diseases and other reasons. 1. Too much fatigue: due to excessive exercise, excessive workload can lead to muscle strain in both lower limbs, excessive lactic acid secretion, and weakness in both thighs. Generally, the symptoms can be relieved after sufficient rest. 2. Calcium deficiency: It is mainly caused by unbalanced diet and malnutrition, which can lead to the symptom of limpness and weakness of both thighs. 3. Lumbar disc herniation: usually aggravated after bending and working, the reason is that it presses on the nerve root, causing lumbago, lower limb pain, numbness of the knee, and aching and weakness of both legs and thighs. Most patients have a history of repeated episodes of low back pain, accompanied by radiating pain in the lower limbs. 4. Chronic disease: chronic disease people have less activity for a long time, weak body, a little activity will be panting, sore legs. There are many reasons for the weakness of two legs, based on the symptoms of the weakness of two legs can not accurately determine the cause, but also need to be combined with the characteristics of the medical history, other test results in order to make an accurate judgment, it is recommended that the cause of the disease under the guidance of a doctor.