Biomechanical modelling approaches which can accurately estimate musculoskeletal functions have offered unique insights into the locomotion of extant animals, which in turn can provide the basis for simulating extinct animal movement. We tested whether Nile crocodiles, which use a variety of limb postures during movement, adopt limb orientations that optimise the moment arms or moment-generating capacities of their muscles during different postures ranging from high walks to more sprawling gaits. We followed a rigorous process in which crocodile dissection data (muscles’ architectural properties) were collected, three specimens were CT-scanned (for segmental mass/inertial properties and skeletal structure; and contrast staining for muscle visibility), muscle lines of action were generated in Rhinoceros 4.0 and inverse simulations were computed in OpenSim 3.3, with kinematic data from experimental XROMM (biplanar fluoroscopy) and kinetic data informed by single-limb force platforms. Results did not fully support the hypothesis that optimal poses are used during different locomotor behaviours. We infer a biomechanical trade-off between executing different postures, meaning that the hindlimb’s leverages are not optimised for any single posture or behaviour. Our model provides 3D estimates of muscle actions in extant crocodiles for comparison with and reciprocal illumination from extinct archosaurs, for reconstructing locomotor evolution.