Hip replacement surgery is a mature surgery to replace diseased joints with artificial prosthesis, which is not necessarily harmful after surgery. A small number of patients may have complications such as postoperative infection, joint dislocation, unequal length of both lower limbs, and deep vein thrombosis of lower limbs. 1. Postoperative infection: due to the poor resistance of patients, intraoperative infection and other factors may lead to infection after hip replacement, manifested as local redness, swelling and pain, generalized fever, etc., and need to actively control the infection, or even need a second surgery to revise. 2. Joint dislocation: If the postoperative position is not proper or the training is not proper, there is also the possibility of joint dislocation, which is manifested as joint pain and activity disorder, and need to consult the doctor in time for reset. 3. Unequal length of both lower limbs: Due to the measurement difference of the length of femur before surgery, the phenomenon of unequal length of both lower limbs may occur, generally the difference of the length of both lower limbs is less than 3 centimeters, which can be adapted gradually through rehabilitation exercises. 4. Lower extremity deep vein thrombosis: after hip replacement surgery, due to fracture trauma, reduced activity, swelling of the limbs, etc., resulting in slow blood circulation, there is a possibility of deep vein thrombosis of the lower extremities, especially in the elderly, which can be manifested as swelling and pain in the limbs. Patients after hip replacement, daily attention should be paid to the protection of the hip joint, avoid strenuous exercise and excessive weight bearing, also need to prevent the occurrence of osteoporosis.