Swimming is indeed the best, but limited by the venue and time, it is not always performed. Hiit, high-intensity aerobic interval exercise can be carried out, and the fat reduction efficiency is also good. Find some action combinations that don't hurt your knees and are more willing to do on some apps, and start to move. Besides, if the knee is not good, the leg can't move at all. Use and waste, exercise properly. My knee is not so good either. I usually run two laps to warm up, and then do a few hiit exercises quickly.