The common causes of postoperative weakness of legs and feet after rectal surgery in the elderly include decline in physical fitness in old age, muscle atrophy, side effects of postoperative radiotherapy, electrolyte disorders, etc. It is necessary to find out the cause of the disease and actively treat the disease in a timely manner. 1. muscle atrophy: too old, the decline of body functions is a normal phenomenon, muscle atrophy leads to weakness of both lower limbs, can strengthen nutrition, adjust the dietary structure, high protein diet, etc., and strengthen the functional exercise, can improve the symptoms. 2. Side effects of postoperative radiotherapy: radiotherapy after rectal surgery may lead to weakness of both lower limbs, and there is no good clinical solution. Postoperative complications are normal phenomenon, but should not be taken lightly, symptoms, need to consult a doctor in a timely manner, a clear diagnosis, identify the cause of the disease, under the guidance of the doctor active treatment.