I'm trying to figure out the anatomy and body posture of juvenile Deinonychus in full speed running/jumpin motion.

I was wondering how big the range of motion is in Deinonychus' hip joint. Are they somewhat restricted in retroflexion as in birds, or would they be able to bend their legs back as far as in the picture below?

PS: Are the limb-head-body proportions actually plausible for a juvenile?

Post's pictures

12200879_10152991654961324_1231212387_n.jpg, 59.62 kb, 960 x 720

No one has done this work specifically (in fact I'm not sure there's a good femoral head and axcetabulum of an adult Deinonychus anyway) and in any case range of motion studies in extinct taxa are fraught with problems as so much of the key informnation (like ligaments) simply isn't there. What would would predict from bones alone is often not a good match for what we know animals can and can't do, so it's of limited value. I would say your picture looks reasonable and that's about the best available.