Figure 11.6 in Rex, sit: digital modeling of Tyrannosaurus rex at rest

Figure 11.6. With the body mass supported by the pubic boot, the hind limbs appear to have been able to shift from (A) a sitting position (with hip flexed) to (B) kneeling on one knee or (C) both knees, without having to lift the body weight off of the pubic boot. Although the axislike insertion of the femur head within acetabulum suggests little femoral abduction was possible, there was likely sufficient flexibility to provide lateral stability. Moreover, the posterolateral angulation of the acetabular axis caused the knees to splay with femoral protracted, again aiding stability against lateral tipping in addition to clearing the rib cage as necessary in locomotion.