When I say that we Mormons believe that God has a body "like man's," we aren't saying that God is a human being. We believe that His body is perfect in form and immortal. We don't believe He is subject to the physical constraints (gravity being one such constraint) that we mortal beings are. Furthermore, we believe that someday we can become as He is now. The Bible says that man is created "in God's image, after His likeness." Just a couple of chapters later, it says that Adam begat a son, and that this son was "in his image, after His likeness." Most Christians will tell you that in comparing man to God, the word "image" means something entirely different than what it means when it is used to compare Adam and his son. We believe the word means the same thing in both instances. We physically resemble God just as Seth physically resembled Adam.
As to God's knee-caps and His quadriceps, I'm pretty such we have no official statement on the subject. Possibly, though, this little snippet might shed a little bit of light on our perspective. In the Clementine Homilies, which is a Jewish-Christian document based on a second-century source, someone questions the Apostle Peter and asks, "I should like to know, Peter, if you really believe that the shape of man has been moulded after the shape of God." Peter responds by saying, "I am really quite certain, Simon, that this is the case... It is the shape of the just God.... For He has shape, and He has every limb primarily and solely for beauty's sake, and not for use. For He has not eyes that He may see when them; for He sees on every side, since He is incomparably more brilliant in His bod than the visual spirit which is in us, and He is more splended than everything, so that in comparison with Him the light of the sun may be reckoned as darkness. Nor has He ears that He may hear; for He hears, perceives, moves, energizes, acts on every side. Bt He has the most beautiful shape on account of man, that the pure in heart, may be able to see Him, that they may rejoice because they suffered. For He moulded man in His own shape as in the grandest seal, in order that he may be the ruler and lord of all, and that all may be subject to Him."
At any rate, if you ask me about God's appendix, I won't be able to give you an answer. I can only tell you that most Mormons, as deluded as most atheists consider us, are not in any way anti-science. Most well-educated Mormons believe in evolution. I know I do. So I suppose it is possible that God's "knee-capss may at one time have transmitted the contractile force of his quadriceps muscles to his shinbones." I really can't say for sure.
That we are essentially the same species as God is a mainstream LDS doctrine, although I haven't heard it expressed in exactly those words. One LDS leader, however, referred to us as "gods in embryo." So you can see that if I'm out of a limb, so was he. Yes, we're pretty unconventional in that regard, which is why the "real Christians" hate us so.