Background <p>To recover lower-limb motor function is a primary goal for rehabilitation after anterior cruciate ligament (ACL) reconstruction. Although quantitative testing and questionnaire evaluation provide a lot of valuable information, functional magnetic resonance imaging (fMRI) provides a powerful method to preliminarily explore the neural recovery process of novel rehabilitation interventions. In this case, we aimed to investigate changes in functional connectivity (FC) of motor imagery-based brain-computer interface (MI-BCI) combined with tDCS intervention in early post-ACL reconstruction rehabilitation, monitored via resting-state fMRI.</p> Case presentation <p>A 38-year-old man patient who underwent left ACL reconstruction received MI-BCI combined with tDCS intervention 5sessions/peek for 4 weeks. before and after the intervention, the resting-state fMRI was assessed. Seed-based analysis was performed using the primary motor cortex (M1) and supplementary motor area (SMA) as the seeds, representing the sensorimotor network (SMN). The results showed increased connectivity between the SMN and specific motor-related (e.g., precentral gyrus, postcentral gyrus, pallidum and paracentral lobule) and sensory information processing areas (e.g., calcarine, lingual gyrus, calcarine, thalamus, posterior cingulum). In addition, decreased FC between both M1 and the bilateral precentral gyrus was observed, and the FC between the left M1, SMA, and the right frontal midline regions was also reduced.</p> Conclusions <p>Our preliminary results showed that MI-BCI combined with tDCS could be an effective method to recovery the lower-limb motor function and promote neural remodeling of an ACL reconstruction patient in early stage. Alterations of the SMN functional connectivity after intervention seems to partially explain the neural remodeling process, if applied on a large sample sizes, could provide more information about specific motor area.</p>