Increased loading of the lateral knee compartment in the unamputated knee during gait in people with unilateral transfemoral/through-knee amputations.

Aims: People with unilateral transfemoral/through-knee amputations (UTF) are at risk of mechanically mediated contralateral knee osteoarthritis (OA). This study aims to identify the mechanical indicators of the development and progression of unamputated knee OA in the UTF population.

Methods: Level-ground gait data were collected from 14 male traumatic UTF participants and 14 uninjured matched controls using optical motion capture systems and force plates. Inverse kinematics, inverse dynamics, and static optimization musculoskeletal modelling simulations were conducted.

Results: UTF demonstrated higher unamputated ankle plantarflexion angles (by 4.9°, p = 0.012), peak-to-peak pelvic obliquity angles (by 2.9°, p = 0.040), and unamputated limb second peak ground reaction force (by 0.1 body weight (BW), p = 0.002) than controls. The UTF unamputated knee maximum loading rate was 0.9 Nm/kg.s higher than controls (p = 0.002). Additionally, UTF presented higher loading of the lateral compartment of the unamputated knee than controls, as characterized by the first peak (by 0.3 BW, p = 0.033), second peak (by 0.8 BW, p = 0.008), and impulse (by 22.0 BW.s/m, p < 0.001).

Conclusion: Traumatic UTF need to adopt new movement strategies to account for the limb loss. Although beneficial for successful ambulation, these compensatory movement strategies increase joint loading in the unamputated knee, which may increase the risk of OA and soft-tissue injuries. Mitigation strategies need to be proposed to improve ambulatory biomechanics with a view to improving long-term musculoskeletal health, while maintaining optimal functional levels.