The specific reasons for catheterization are as follows: 1. When arthroscopic surgery is performed, it may take a long time and the patient is not able to urinate on his own at this time, so some precautions should be taken, that is, catheterization first. 2. During the procedure, the anesthesiologist may manage the patient’s fluids, that is, there may be a large amount of rehydration. The patient’s urine may increase a lot in a short period of time, and at this time the patient is still not able to urinate on his own, so catheterization is also necessary. 3. Due to anesthesia, it is possible that the patient may become incontinent or retain urine for a period of time, so it is also necessary to catheterize in advance to prevent this type of situation. The urinary catheter can be removed only after the operation, when it is confirmed that the patient is able to urinate on his own.