Unlike knee replacements, hip replacements involve the length of both legs, and it is possible that one leg will be longer or shorter after surgery. If the affected leg is longer after surgery, insoles should be placed on the healthy side, and vice versa. Generally, over 90% of patients do not need insoles after surgery. In cases where the difference in length between the two limbs after surgery is within 1 cm, patients rarely experience discomfort and do not need insoles. Only in some special cases where the difference in length is greater than 1 cm, insoles are required. The reason for this is to prevent the lumbar spine from being affected by unequal limb lengths, which can lead to scoliosis, lumbar degeneration, bone and joint pain, lumbar pain, leg numbness, and other symptoms. It is important to know that once the lumbar spine disease is caused by unequal limbs, it is often very difficult to repair. As for how high the insole actually needs to be padded, the general principle is that the difference is how much padding. The measurement method is: when the patient’s legs are not equal, take off the shoes and stand on the floor, put the paper under the bottom of the foot of the side that feels short, and then keep increasing the thickness of the paper until the patient himself feels that the feeling of the two feet on the ground is the same, the thickness of the paper is basically the thickness of the insole. Generally speaking, the height of the insole that the patient needs is 1~3cm. However, it is worth noting that if the patient’s legs are more than 3 centimeters apart, the insole needs to be padded gradually, not 3 centimeters at once. Because these patients are in a long-term state of great difference in the length of the two legs, the lumbar spine is often already affected, if the insoles are high at once, the patient will feel that the short side of the leg has become longer, the waist can not stand. At this time, the patient needs to start with a 1 cm insole, adapt to 4-6 weeks, then increase to 2 cm, and finally gradually transition to the height of the need to pad. As for how long the insoles need to be padded, generally speaking, the greater the difference between the length of the two legs, the longer the insole time. In other words, if the difference between the two legs within 1 ~ 2 centimeters, generally 1 year insoles, the body can accept and adapt to such a gap; the difference between the two legs 2 ~ 4 centimeters, insoles may have to pad a long time, 5 years or even longer is possible, because in a short time, the body is difficult to adapt to such a gap, only until the waist slowly compensate, to gradually adapt; if the two legs length difference of more than 5 centimeters, it is possible to need to pad the insoles for a longer period of time.