BackgroundGait initiation (GI) is an important functional task related to balance and gait performance. In addition, it has predictive importance for falls and postural instability in patient with multiple sclerosis (MS). However, it is uncertain how GI is affected in patients in the early stage of MS (Expanded Disability Status Scale (EDSS) ≤3). In this study, it was aimed to investigate the anticipatory postural adjustments (APAs), posterior center of pressure (COPap) displacement, and spatiotemporal variability during GI in patients with and without functional loss in the early stage of MS. MethodsForty-four participants (31 MS patients and 13 healthy subjects) involved in this prospective cross-sectional study were divided into three groups: Group-I: Patients without functional loss (EDSS 0 to 1.5) (n = 14), Group-II: Patients with functional loss (EDSS 2 to 3) (n = 17) and Group-III: Healthy subjects (n = 13). Electromyographic activity of the bilateral tibialis anterior (TA) and gastrocnemius medialis (GM) and COPap displacement were recorded during the postural phase of GI. Additionally, spatiotemporal parameters were recorded within the first three steps, and the coefficient of variation was calculated with 40 walks for variability. ResultsThere were significant differences in the Kruskal-Wallis tests of variables (p<0.05). Group-I demonstrated smaller APAs magnitudes in TA [stance (p = 0.01), swing (p = 0.01)], GM of swing limb (p<0.0001), and smaller COPap displacement (p<0.0001) compared to group-III. Group-II demonstrated smaller APAs magnitudes in all muscles (p<0.0001) compared to group-III and the smallest COPap displacement (p<0.0001). Group-I showed a significant increase in stride width variability compared to group-III (p = 0.01). Group-II showed a significant increase in several variabilities [first stride length (p<0.0001), second stride time (p<0.0001), first double support time (p<0.0001), stride width (p<0.0001)] compared to group-III. ConclusionPatients in the early stage of MS had impairment in both the postural and locomotor phases of GI with more obvious in the patients with functional loss. The results indicate that MS patients without functional loss have difficulty initiating gait. Although there is no functional loss, the patients have a risk of falls, postural instability, and gait impairment due to their inability to initiate gait effectively. As a result, rehabilitation is necessary even if there is no functional loss in patients with MS.