Knights were part of the second estate, the members of the noble class who owned land and were welcome and sometimes required in courts. Since they owned land there was a certain power behind them, and of course, they were the warriors who fought in wars. For a man to become a knight he would have needed to have some wealth already; knights had to acquire their armor, horses, and weapons themselves, and poor-quality armor, weapons, or animals could have easily meant their lives. Medieval times had a fairly cut-and-dry society: the first estate consisted of clergymen like priests, the second estate consisted of the landowners and nobles, and the third estate essentially ensured the first two estates were well cared for. Knights had peasants of the third estate to work on their land. Although this arrangement did leave a certain obligation for the knights to protect and care for the people working on their land, knights are said to have exploited peasants for their labor, rent, agricultural products, and other necessities.
Ultimately, each estate or class had its own very clear and known part to play to keep society in order and functioning like a well-oiled machine. As warriors with noble titles, knights were part of the second estate.