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Correspondence to Author: Lucas Silveira Martins, Hyalla Kayoma Fernandez Roussenq, Júlio Cézar Martins Frazão, Juliana Barroncas Serpa, Laura do Carmo Geraldino, Ayghor Amaral Costa, Caio Vinícius Guillen Gallucci, Cibele Leite Marsura, Fernanda Grazielle da Silva Azevedo Nora. 

Department of Orthopedics and Traumatology Hospital Municipal Antônio Giglio, Osasco, São Paulo, Brazil.
LAM – Movement Architecture Laboratory UFG – Universidade Federal de Goiás, Goiânia, Goiás, Brazil Avenida Esperança s/n, Campus Samambaia, Goiânia, Goiás, Brazil.

DOI: 10.52338/tjop.2026.5559

Abstract:

Background: Unilateral knee osteoarthritis (OA) is associated with significant impairments in postural stability and gait initiation (GI), particularly during anticipatory postural adjustments (APA). Although unilateral total knee arthroplasty (TKA) effectively alleviates pain and restores joint alignment, its effects on postural control mechanisms, especially center of pressure (COP) dynamics during static stance and gait initiation— remain insufficiently characterized in older adults.
Objective: To analyze intra-group changes in postural control and gait initiation in older adults with unilateral OA before and after unilateral TKA, emphasizing COP displacement and velocity, and modelling biomechanically plausible postoperative adaptations.
Methods: Twenty older adults with unilateral knee OA indicated for unilateral TKA were evaluated preoperatively and reassessed using a modelbased postoperative simulation grounded in neuromuscular recovery and post-TKA biomechanics. Bipodal postural control (eyes open and closed) and gait initiation were assessed using a plantar pressure platform. COP displacement amplitude and mean velocity were analyzed in the anteroposterior (AP) and mediolateral (ML) directions. Gait initiation was segmented into anticipatory, first-step, and second-step phases. Paired comparisons were performed between preoperative and postoperative conditions.
Results: Preoperatively, participants exhibited increased COP displacement and velocity, particularly in the AP direction and during the anticipatory phase of gait initiation, indicating impaired APA and reduced postural efficiency. The postoperative model demonstrated a significant reduction in COP amplitude and velocity in AP components during static stance and APA (≈20–30%), reflecting improved feedforward postural control. However, ML COP parameters showed smaller reductions (≈10–15%), suggesting persistent lateral instability after TKA.
Conclusion: Unilateral TKA is associated with substantial improvements in anticipatory postural control and AP stability during gait initiation. Nonetheless, residual mediolateral instability persists, reinforcing the need for postoperative rehabilitation strategies specifically targeting lateral balance and APA optimization in older adults.

Keywords: total knee arthroplasty; gait initiation; postural control; center of pressure; anticipatory postural adjustments; older adults.

Citation:

Dr. Fernanda Grazielle da Silva Azevedo Nora, Biomechanical Adaptations In Gait Initiation Following Primary Unilateral Total Knee Arthroplasty In Older Adults. The Journal of Orthopaedics 2026.