First of all, you can squat against the wall. Squatting against the wall means that the back is leaning against the wall, the legs are open, the knees are bent and crouched for half, the included angle between thighs and calves should not be less than 90 degrees, the legs should not be too wide, and the toes should face outwards. In this process, you will feel that your thighs are super tight, and you can stick to it, just three to five times a day. This method can make you exercise your thigh muscles.
Secondly, you can lift your legs high. You can choose to lie flat or prone, straighten your feet and lift up 30 degrees. If you are tired, you can change your other foot. Anyway, you can do it when you have time. This method is what the doctor told me, and it can also exercise the small muscles of the legs.
Muscle is the most important tissue to protect the knee, and the reason why the knee is not good is mostly because of poor muscle strength. Both methods can increase thigh muscles, and the effect is quite fast. Sitting against the wall for a week or two feels that the thigh muscles are much stronger, which may also be because the thigh muscles were weak before. There are also corresponding action instructions on the Internet. You can also check them. Personally, I think it is very useful to exercise muscles to avoid knee injury.