Altered Brain Activity During Joint Loading After Anterior Cruciate Ligament Reconstruction

Abstract

Following an anterior cruciate ligament rupture, many patients that undergo surgical intervention (ACLR) fail to return to pre-injury levels of physical activity due to repetitive “giving-way” episodes. This functional joint instability may result from an insufficient neural processing responsible for neuromechanical links between the ACL and central nervous system. It remains unclear how the brain of the ACLR patients perceives mechanical loading compared with healthy controls. PURPOSE: To examine brain activity differences between ACLR patients and healthy controls during knee loading. METHODS: Seventeen healthy control (CON: 26.9±5.6yrs, 69.6±1.2kg, 166.3±7.7cm) and seventeen ACLR patients (ACLR: 22.29±3.8yrs, 67.8±18.7kg, 164.5±10.4cm) volunteered. Somatosensory cortical activity was measured using event-related desynchronization (ERD: % decreased power; ERD1, ERD2, ERD3) from electroencephalography (EEG) during each second of an anterior knee loading (3sec) at constant force (45N/sec). Comparisons were made using 2-way ANOVAs with one within factor (limb, 2 levels) and one between factor (group, 2 levels). RESULTS: A significant limb by group interaction was observed for ERD1 (F[1,32] = 8.280, p = .007). The reconstructed knee in the ACLR showed greater increased cortical activity than the matched limb in the CON (36.4±11.5 vs. 25.3±13.2%, p = .013), while the uninjured knee in the ACLR was similar to the CON’s matched limb (25.1±14.2 vs. 28.0±11.5%, p = .506). Additionally, the ACLR showed greater increased ERD1 in the reconstructed limb when compared to the uninjured limb (36.4±11.5 vs. 25.1±14.2%, p = .006). No significant interactions or main effects were observed for ERD2 and ERD3. CONCLUSION: Following an ACL rupture, the injured leg exhibits increased brain responses during early loading compared to the uninjured knee, as well as the matched limb of healthy controls. This may indicate protective neural adaptation in the brain to compensate the altered proprioceptive input from the injured knee, such that reorganized somatosensory cortex activity can optimize neuromuscular control needed for maintaining functional joint stability. Future studies should explore whether this neural adaptation improves joint health and junction after an ACL injury.