This symptom can be caused by a variety of diseases, and the causes of this symptom are: 1, varicose veins in the lower limbs, when varicose veins in the lower limbs appear, it will make the legs feel heavy and difficult to walk; 2, spinal cord cervical spondylosis, when the protruding disc compresses the spinal cord, it will lead to weakness in the lower limbs and unstable walking; 3, cerebrovascular disease, when the cerebral blood vessels are narrowed, resulting in insufficient blood supply to the brain. When the cerebral blood vessels are narrowed, resulting in insufficient blood supply to the brain, there will be symptoms of unstable walking and sunken legs; 4, hypokalemia, when the blood potassium is low, it will lead to muscle weakness, walking with sunken legs, walking difficulties; 5, local cold overexertion, will also lead to walking with sunken legs can not lift the symptoms; 6, lumbar disc herniation, lumbar disc herniation compression of nerves, will lead to walking with sunken legs.