This study evaluates the biofidelity and response characteristics of the Thor Lx dummy lower extremity prototype. Static and dynamic tests were performed to evaluate its response relative to that of cadavers and the Hybrid lll (45° dorsiflexion ankle and softjoint stop). Static tests determined the ankle joint moment properties, axial stiffness, and the mass and moments of inertia. The three different limbs were subjected to two different types of dynamic tests:​ pure dorsiflexion and a combination of dorsiflexion and axial load. The results show that the response characteristics of the Thor Lx better reflect those of the cadaver limbs, which indicates that the Thor Lx design is an improvement over the Hybrid III. The continuous ankle joint stiffness eliminates joint property discontinuities at the extreme ranges of motion, and the nonconcentric joint locations of the Thor Lx mimic the ankle and sub-talar joints in the human. The Achilles tendon of the Thor Lx serves as passive musculature and increases ankle stiffness in dorsiflexion. A compliant element in the tibia shaft gives more biofidelic tibia axial load characteristics, and the straight shaft eliminates artificial moments created by axial loading. With its design modifications and comprehensive instrumentation package, the Thor Lx is capable of providing a more complete and biofidelic assessment of lower limb response and injury risk.