God’s intention for His Son is to exalt Him above all creation! He humbled Himself more than any one ever and now he will experience God’s promise of exaltation more than anyone ever. God gave Him a name that was 
above every other name (Philippians 2:9) and then the text continues that the exaltation will be of such that “…at the name of Jesus every knee should bow, in heaven and on earth and under the earth” (Philippians 2:10). This is universal Lordship! This is universal subjugation of all things, and all people, and all beings to the person of Jesus Christ. It does not imply, as some argue, “universal salvation.” One day, every human being will face the Lord Jesus. Those who have worshiped Him in this life will rejoice as they proclaim his sovereignty and universal right to reign. Those who have rejected Jesus will also acknowledge His universal right to rule yet there probably won’t be much rejoicing for them (Gross understatement!).
Every knee will bow. “Those in heaven” probably refers to the heavenly angels! It might also refer to those saints who have passed away and have joined Christ in Paradise. They will surely rejoice with all the rest of the believers. “Those on the earth” probably refers to those who are alive at His coming to meet the believers of the church age at the time of the rapture. “Those under the earth” according to most commentators, most likely refers to the fallen angels. Yet, I’m not certain that it doesn’t also refer to the unredeemed of every age. But regardless of the specifics of these three phrases, I’d suggest they are put together to focus on the fact that everyone and everything you can imagine will be included. There are no exceptions to whom or what will acknowledge the Lordship and Kingship of Jesus. Everyone will!
As a boy growing up in the Catholic Church I learned how to genuflect. As an altar boy I did it a lot. It was rather an insignificant gesture and I did it because I was taught to do it. But, really, that’s our physical bowing or bending of the knee to God. Thomas Aquinas, the most famous Catholic theologian, said, “Just as prayer is primarily in the mind, and secondarily expressed in words, so too adoration consists chiefly in an interior reverence of God, but secondarily in certain bodily signs of humility; thus when we genuflect we signify our weakness in comparison with God.” In the New Testament there are two words for “worship.” One means to bow the head and the other means to bow the knee. The significance is worship. We don’t bow the knee before the President. We don’t bow the knee before any institution, before the altar of technology, before any program or before our salaries. God alone is worthy of our worship. We bow and bend before God and God alone. My wife and I found that bending the knee and bowing our heads, when we prayed together brought radical healing to our relationship. It’s humbling and healing to get down on our knees and bow our heads in prayer.