I'm not totally sold that there isn't knee articulation there. Hasbro's tricky when it comes to armored figures, so I'm not going to hollar before I'm hurt on that one just yet... I agree though, the ankle joints are apparant, and if they're there without knees, that's always been a pet peeve of mine with Hasbro.
They did it with Sora Bulq, Neimoidan Warrior, Heir to the Empire Luke, and others. It's really some terrible decision-making by Hasbro designers, and something I believe's been addressed in Q&A... If it hasn't, it ought to be anyway.
And yet, Commander Cody got knee joints, but they sculpted his ankles in such a horribly pre-posed fashion that he turned out to be one figure that really needed those points of articulation. Same with the Training Fatigues Clonetrooper out now... Go figure.