The common clinical causes of weak and achy legs include lumbar spine disease, arteriosclerosis, overwork, anemia, and weaker physique. It is recommended that people with symptoms of related diseases should seek medical treatment. 1. Lumbar spine disease: lumbar disc herniation and lumbar spinal stenosis, there will be spinal cord and nerve root compression, muscle weakness of the corresponding innervated area, the patient will feel the lower limbs are weak and achy, and after the activity, it will lead to obvious pain symptoms. 2. Arteriosclerosis: patients due to lower extremity arteriosclerosis occlusive disease caused by activity will appear pain, usually numbness or feel cold, there are obvious symptoms of weakness, this disease occurs more often in elderly patients. 3. Excessive fatigue: part of the population in the body in frequent strenuous exercise or prolonged physical labor state, limbs easy to excessive fatigue and muscle weakness. It is recommended that such people should take proper rest to ease the discomfort. 4. Anemia: part of the population due to dietary imbalance, disease caused by blood loss and other factors, the body lacks hemoglobin, the oxygen supply to the tissue cells is weak, easy to cause limb weakness, mental depression. 5. Physical weakness: this situation is also known as physical weakness, the body due to underdeveloped muscles or congenital muscle weakness, when ordinary exercise will still cause a serious burden on the limb muscles, clinical manifestations of limb weakness, soreness and pain. This situation requires a gradual approach to exercise recovery. There are more diseases that appear leg weakness, it is recommended that patients with symptoms of leg weakness go to the hospital in a timely manner, do not delay diagnosis and treatment.