Postural control characteristics as reflected by center of pressure measurements in anterior cruciate ligament reconstruction patients at varying post-operative stages: a cross-sectional comparative study.

OBJECTIVE: To compare center of pressure (COP) characteristics and postural control changes in anterior cruciate ligament reconstruction (ACLR) patients across distinct post-operative phases and to establish quantitative evidence for post-operative functional assessment.

METHODS: This cross-sectional controlled study enrolled participants prospectively. One hundred ACLR patients (n = 100) were stratified into five post-operative cohorts: Group A (1.5-3 months, n = 20), Group B (3-6 months, n = 20), Group C (6-9 months, n = 20), Group D (9-12 months, n = 20), and Group E (≥ 12 months; mean ± SD: 16.9 ± 3.3 months, n = 20). A control group of 20 healthy individuals without history of lower limb injury (Group F) was included. All ACLR patients underwent standardized rehabilitation protocols according to institutional guidelines. The Zebris plantar pressure analysis system was used to measure center of pressure trajectory parameters at self-selected comfortable walking speed, including gait line length, single-limb support line length, anteroposterior displacement, and mediolateral displacement. Limb symmetry indices were calculated by comparing the operative and non-operative limbs, and postural control differences across post-operative stages were determined through between-group comparisons.

RESULTS: Gait line length and single-limb support line length were significantly shorter on the operative limb compared with the non-operative limb (P < 0.05), whereas no significant bilateral differences were observed in the control group (P >  0.05). Between-group comparisons revealed significant differences in center of pressure parameters across the post-operative stages (P < 0.05). Gait line length in Groups A through E was reduced by 30.0%, 15.3%, 11.1%, 6.8%, and 2.0%, respectively, relative to the control group. Single-limb support line length demonstrated corresponding reductions of 83.4%, 54.0%, 34.8%, 20.6%, and 16.1%, respectively, from Groups A through E. Anteroposterior displacement in Groups B and C was significantly greater than in the control group, whereas mediolateral displacement in Groups A, B, and C was significantly greater than in the control group (P < 0.01).

CONCLUSION: Patients in the post-operative ACLR cohorts demonstrated abnormal center of pressure parameters and significant functional asymmetry between limbs. Center of pressure parameters across all post-operative timepoint groups were lower than in the healthy control group, indicating that center of pressure-based postural control assessment provides objective quantitative metrics for post-operative functional evaluation.