Wiktionary
n. An order which (at least mainly) consists of members who receive and/or most have the knighthood, hence constitutes an honorific brotherhood (in modern times often open to both genders, in rare cases a sisterhood) of knights (and/or, as female equivalent, dames). The hierarchical structure, purpose, activities (in many cases rare and mainly ceremonious), titles and insignia vary widely.
Usage examples of "order of knighthood".
And then Sir Launcelot gave him the order of knighthood, and then Sir Gareth prayed him for to depart and let him go.
Take them joyfully, and come with me to Arthur to receive the order of knighthood, for thou dost merit it.
At these words he drew that famous sword, Joyeuse, and, while Ogier and the rest knelt before him, gave them the accolade conferring on them the order of knighthood.
He was Preceptor of the palace's chapter of Albonate Knights, which was a military order founded for the protection of the King's person, and the only order of knighthood in Ile-Rien that still meant more than a courtesy title.
What would you think if I formed a special order of knighthood, for my own knights only.
So recall you always your holy vows to God and your order of knighthood and honor them, lest you forever damn your immortal soul.
The loyalty in this case is of two degrees or commitments: first, to the chosen adventure, but then, also, to the ideals of the order of knighthood.