The main causes of weak and feeble legs are anemia, poor physical condition, malnutrition, back disorders, hip joint disorders and knee joint disorders. 1. Anemia: anemia, even severe anemia, lower gastrointestinal bleeding, black stools lead to hidden blood loss, anemia, leading to leg weakness. 2. Poor physical condition: Poor sleep and night shifts lead to poor physical condition, which can lead to weakness and tenderness of the legs. 3. Malnutrition: anorexia, malnutrition, and lowered albumin can also cause leg weakness. 4. Lumbar diseases: the nucleus pulposus of lumbar intervertebral disc herniation compresses the nerves innervating the legs, resulting in weakness of the legs. 5. Hip joint disease: osteoarthrosis of hip joint, necrosis of femoral head, tuberculosis of hip joint, septic infection, etc., which leads to the lesion of hip joint, can easily cause leg weakness, not dare to exert oneself, not dare to walk, and so on. 6. Knee joint disease: serious lesions of the knee joint lead to leg weakness. Weakness of legs may also be related to cerebrovascular disease, endocrine diseases, etc. It is recommended to consult a doctor in time to clarify the cause of the disease under the guidance of the doctor.