If you have been relatively healthy all of your life, you probably have not given much thought to how much you put your knees through. You rely on properly functioning knees for everyday activities like walking, sitting, standing, climbing up and down stairs, and even driving. When you add in activities like physical labor, athletics, dancing, or other strenuous pursuits, good knee function is critical to your overall physical performance. Knees help you move, keep you upright, and bear your weight.