Spatiotemporal lower-limb asymmetries during stair descent in athletes following anterior cruciate ligament reconstruction

Purpose: This study evaluated motor control recovery at different times following anterior cruciate ligament reconstruction (ACLR) by investigating lower -limb spatiotemporal symmetry during stair descent performances. Methods: We used a cross-sectional design to compare asymptomatic athletes (Controls, n = 18) with a group of people with ACLR (n = 49) divided into three time-from-ACLR subgroups (Early: <6 months, n = 17; Mid: 6-18 months, n = 16; Late: >= 18 months, n = 16). We evaluated: "temporal symmetry" during the stance subphases (single -support, first and second double -support) and "spatial symmetry" for hip -knee -ankle intra-joint angular displacements during the stance phase using a dissimilarity index applied on superimposed 3D phase plots. Results: We found significant between -group differences in temporal variables (p <= 0.001). Compared to Controls, both Early and Mid (p <= 0.05) showed asymmetry in the first double -support time (longer for their injured vs. non -injured leg), while Early generally also showed longer durations in all other phases, regardless of stepping leg. No statistically significant differences were found for spatial intra-joint symmetry between groups. Conclusion: Temporal but not spatial asymmetry in stair descent is often present early after ACLR; it may remain for up to 18 months and may underlie subtle intra- and inter -joint compensations. Spatial asymmetry may need further exploration.