But dinosaur fossils suggest that it's not that simple. Rothschild said it seems the type of joint has more to do with osteoarthritis than weight. Sauropods have simple hinge joints at the knee that allow the leg only to bend. Humans, on the other hand, are also able to twist the leg bones. One place sauropods were thought to develop arthritis is in the tail.
Many sauropod skeletons have several tail vertebrae fused together.
Instead, modern illustrators and skeleton assemblers now show these dinosaurs carrying their tails high off the ground. Both the Apatosaurus and Diplodocus fossil skeletons on display at the Carnegie feature sections of fused vertebrae. Though both are configured in the old style, with tails dragging behind them, the fused section in each skeleton is above the portion of the tail in contact with the ground. Dawson said some scientists had argued that these dinosaurs used their tails like bullwhips, snapping them to make a loud noise. But again, she noted, the fused sections are nowhere near the tips, where stress would be greatest.