The whole body structure depends on the joints, one of them being the knees, which carry the key function. All activities, such as walking, running, holding in the right posture, jumping, and standing, are being performed by your body thanks to your knees.
Still, over time, knees can become loose and damaged due to some injuries and wounds. Ligaments and tendons can lose their flexibility because they lose their natural lubrication.
However, you have to keep your knees strong, regardless of your age and other factors. They have to always be ready for sudden and fast movements.
The same goes for your tendons and ligaments as well, since the support of your entire body depends on their flexibility and strength.