# Analysis of Spatiotemporal Gait Variables before and after Unilateral Total Knee Arthroplasty
## 1 Introduction  
Knee osteoarthritis (KOA) is the degenerative disease that causes the greatest loss of mobility in the elderly [1]. In Portugal, the prevalence is about 15.8% in females and 8.6% in males [2]. Patients with KOA have limited mobility, reflected as a reduced range of motion and functional impairment [3]. The risk of developing knee osteoarthritis involves a complex interaction between intrinsic factors, such as bone density and morphology, sex hormones, and trauma, and mechanical factors, such as joint overload. However, the greatest risk factors are age and obesity, the increasing rates of which in the populations of developed countries make the increase in knee osteoarthritis an expected phenomena [4].  
TKA is the key surgical treatment for severe KOA because it effectively reduces pain and functional impairment, improves quality of life, and enables autonomy in daily activities [5; 6]. Despite reports of gait improvement after TKA, it also has been suggested that those are not sufficient to accomplish values comparable to healthy age-matched subjects [1; 6; 7; 8; 9; 10], raising the need to better understand the nature and extent of these gait improvements [9; 11; 12].  
However, after unilateral TKA, altered gait mechanics, including increased joint loading and reduced knee flexion excursion, may contribute to the progression of contralateral KOA. After TKA, individuals often favor the contralateral limb during weight-bearing tasks, potentially leading to increased forces and adduction moments at the contralateral knee [10; 13; 14]. This increased dependence on the contralateral knee may be a contributing factor to the radiographic progression of KOA in that knee. Further exploration is warranted to fully understand these dynamics and develop strategies to mitigate the risk of contralateral KOA progression [1; 10].  
Gait analysis has become an important tool for evaluating KOA and TKA patients, as it provides objective measures of kinematic and kinetic parameters that relate to the patient's functional capacity [9]. Spatiotemporal parameters, such as gait velocity and cycle length, and the duration of its phases, are easily obtained and provide valuable insights into gait patterns. While spatiotemporal and kinematic gait parameters are generally believed to improve in the medium to long-term following TKA [6; 8; 15; 16; 17], the incomplete recovery of normal knee joint function and impaired gait pattern are often reported when compared to asymptomatic controls [1; 7; 9; 10; 14; 18; 19]. Specifically, studies have shown that KOA patients exhibit slower walking velocity, shortened step length, and lower cadence than healthy individuals [3; 6; 15; 18; 20]. However, improvements in stride time and length were reported after TKA [21]. Nevertheless, knowledge gaps and limitations in post-TKA gait assessment research have been previously identified, and few published works have studied the effect of TKA on the gait parameters of the non-surgical limb [17].  
TKA outcomes are influenced by multiple factors [10], making essential a comprehensive post-TKA assessment that considers both general improvements and biomechanical adaptations. While evidence regarding the effect of TKA in the surgical and non-surgical limb is available [1; 22], the effect of limb dominance is a less explored aspect that deserves analysis, as it can guide rehabilitation strategies and improve postoperative care. Thus, the aims of this study were (a) to evaluate the spatiotemporal gait variables of patients before (pre-) and after (post-) TKA surgery, and (b) to investigate the influence of the surgical side dominance on these variables.