Background: Since the fibula is linked to the ankle as well as the knee joint, its importance for knee and ankle disabilities should be investigated. This study evaluates its movement during range of motion of the ankle. Materials and Methods: An instrument, together with the experimental protocol, was devised to determine the relative motion of the fibula in reference to the tibia with motion of the ankle joint on 20 paired lower extremity cadaver specimens. Results: It was demonstrated in all specimens that the fibula had a relative rotation around its longitudinal axis and mediolateral translation with reference to the tibia with ankle motion. The distal end of the fibula rotates more compared to the proximal end. The mediolateral translation of the proximal end of the fibula is rather close to that of the distal end. Although there was no consistent pattern for rotation, dorsiflexion caused lateral translation and plantarflexion caused medial displacement for most of the specimens. Conclusion: A novel, invasive but relatively simple test setup was devised. Movement of the fibula which is important for the kinematics and kinetics of the knee and ankle joints was evaluated by this new device. Clinical Relevance: Evaluation of the fibula movement in normal lower extremities may lead to better understanding of its dynamic function which could have treatment implications for pathological conditions.