Relation between genu and genomos

Greek gnomon is a carpenter's square, i.e. a right angle. Right means straight up, square, correct, the strong arm, a legal privilege. The common meaning to all those things is strength. You have a right to life, but only if you are strong enough to cling to it. You have a right to the space you occupy, but only if you are strong enough to defend it. You have a right to own property, but only if you can guard it from all attackers. You may obtain the services of a champion to defend your rights, or create a government for that purpose, but of course the champion's loyalty might become a concern, and governments always eventually renege on the contract.

There is no relation to a knee. Latin genu is a separate word with it's own declensions. Genomos is descended from genomus, related to gnoma, knowledge.