Center of pressure predicts Intra-limb compensatory patterns that shift demands away from knee extensors during squatting.

The persistence of knee extensor moments deficits following anterior cruciate ligament reconstruction (ACLr) may be attributed to difficulty quantifying inter- and intra-limb compensations clinically. Force plate derived center of pressure (CoPpos) and vertical force (vGRF) may provide valuable information regarding limb and joint loading impairments in this group. This study aimed to determine the: 1) relationship between measures CoPpos and intra-limb extensor moment distribution during a squat, and 2) utility of using CoPpos and vGRF to estimate knee extensor moment deficits post-ACLr. Twenty-four individuals, 142 ± 22.5 days post-ACLr, performed bilateral squats. Ankle (aEXT), knee (kEXT) and hip (hEXT) extensor moments were calculated using three-dimensional kinematics and GRF. Moments, CoPpos and vGRF were identified at peak kEXT. Intra-limb moment distribution was characterized using hEXT/kEXT and aEXT/kEXT ratios. Linear regressions analyzed relationships between CoPpos and hEXT/kEXT and aEXT/kEXT. Stepwise regressions determined if between-limb CoPpos ratio predicted between-limb ratios of hEXT/kEXT and aEXT/kEXT. Stepwise regression determined if between-limb CoPpos and vGRF ratios predicted between-limb kEXT ratio. Results found that CoPpos predicts intra-limb moment distribution (hEXT/kEXT and aEXT/kEXT); more anterior CoPpos related to higher moments at the hip and ankle relative to the knee. In addition, between-limb CoPpos ratio predicts between-limb ratio of hEXT/kEXT and aEXT/kEXT ratios. Together between-limb CoPpos (52%) and vGRF (18%) ratios explained 70% of the variance in between-limb kEXT ratios (R2 = 0.70, p < 0.001). These data suggest that force plate derived CoPpos and vGRF may be important for detection of knee extensor moment deficits in individuals post-ACLr.