Everyone knows that sitting for a long time can harm the waist, but did you know? Sitting for a long time can also harm the knees. Fan Meng, Deputy Director of Orthopedics at Tianjin First Central Hospital, said in an interview with People's Daily Online that many people believe that sitting is "nurturing" their knees. In fact, prolonged sitting can affect the blood circulation of the knee joint, reduce the nutrient transmission of the joint synovial capsule, and over time can cause muscle atrophy around the knee joint, resulting in knee joint injury and pain. Fan Meng said that the knee joint, as an important component supporting upright walking in the human body, once damaged, not only affects motor function, but also affects quality of life. It is recommended to get up and move around every 30 to 45 minutes of sitting to promote blood circulation in the lower limbs. Fan Meng and orthopedic medical staff bring four training exercises to help you stay away from knee pain and prevent knee injuries. Action 1: Sitting in a chair with legs straight up, moving your body forward, keeping your waist straight, and placing your hands in front of your thighs; Lift your right leg, try to straighten it as much as possible, tilt your toes upwards, and keep your knee joint straight for 10 seconds before putting it down; Perform the same action with the opposite leg. Do each leg 20 times. Action 2: Sitting in a chair with knees extended and bent, moving your body forward, keeping your waist straight, and placing your hands in front of your thighs; Lift the right leg, bend the knee joint as much as possible, straighten the leg, tilt the toe upwards, and keep the knee joint straight for 3 seconds before lowering it down; After doing 10 times, switch to the opposite leg and do the same action. Do each leg 20 times. Action 3: Stand on tiptoe, with the toes facing forward and shoulder width apart; Stand on tiptoes, exert force on the soles of the feet, with the front foot as the negative focus. Keep the lower limb muscles still and hold for 10 seconds before releasing. Do 20 times. Action 4: Stand in a slightly bent knee position, with the toes facing forward and shoulder width apart; Mild forward flexion of both knees, with the front of the knee joint level with the toes, not exceeding the toes, and not tilting inward or outward; Keep the lower limb muscles firmly still, keep the upper body upright, and stand up after 20 seconds. Do 20 times. (Lixin News Agency) (Reporter Yan Yan)