This lever model could be too simple as there are different loads and efforts acting on these levers in the course of a step cycle. Did you consider body weight as a major load acting on all hindlimb bones or only loads related to propulsion or to the elevation of the limb? Further point: Efforts (E) might be applied through muscles.

Have you considered the fact that multijoint muscles act as part of closed kinematic chains? Levers are open kinematic chains, so modeling the joints solely as levers may not be appropriate.

Michael- I have not consider body weight, but instead propulsion loads, so the femur, tibia and pes. To give greater accuracy, how would I factor in body weight. Could you elaborate on your further point perhaps? Does this mean that muscle size is more important?

Stephen - Would this not be a better example of Functional kinematic chains as within human locomotion, one foot swings while the other stabilises, surely this would also be apparent in quadrupeds?

Thank you

Closed kinematic chains potentially exist wherever and whenever multijoint muscles exist. This would pertain to all species. It is well described as functioning in fishes, amphibians, horses, crustaceans, etc. It is also exemplified in the cruciate ligaments of the knee, from reptiles to mammals, including the human animal. I am not sure why we do not pay more attention to it.

I assume that these are closed chain kinetics.  If the vertical ground reaction force is known and joint kinetics (moments) are known then you could calculate mechanical advantage (in sagittal plane) by calculating the moment arms using the joint moment divided by the vertical ground reaction force for each joint and compare moment arms between the joints.  I understand that this may not be experimental data, but this method should work with experimental data.

There is a lot going on here during   normal gait.  Remember that the hamstrings are working during terminal extension to decrease loading forces (1) and there is a kinetic loading of the primary pelvic ligaments to drive counter rotation of the trunk to decrease loading to the femoral head. (2)  This is in the area of biotensegrity of which Steve is the expert.

1.  DonTigny, RL: Terminal extension exercises for the knee. Phys Ther 52:45, 1972

2. DonTigny, RL: Technical Report

Researchgate.com

DOI: 10.13140/RG.2.2.29972.50561

The Sacral X Axes; Location, Structure, Movement, Kinetic Loading, Function,

Biotensegrity Technology and Pathology. The essential pieces of the low back pain puzzle.