Inter-joint coordination and coordination variability during gait differentiate copers from noncopers in males with anterior cruciate ligament deficiency.

Anterior cruciate ligament deficiency (ACLD) leads to knee instability and altered gait patterns. Individuals with ACLD can be classified as copers or noncopers. Lower-limb coordination and coordination variability may reflect compensatory strategies and risks of secondary injury. This study aimed to compare lower-limb coordination and coordination variability between copers and noncopers with ACLD during gait. Forty-two males with ACLD (22 copers, 20 noncopers) and 26 age-matched healthy controls participated. Kinematic data during walking were collected using an eight-camera motion capture system at 120 Hz. Coordination patterns and coordination variability during gait subphases were analyzed using vector coding for hip-knee, knee-ankle, and hip-ankle couplings in the sagittal plane. The only significant difference in coordination pattern was found for the hip-ankle coupling during swing, where copers showed higher frequency than noncopers (p = 0.038, d = 0.3). For coordination variability, noncopers had higher hip-ankle variability during initial contact/loading response than controls (p = 0.0064, d = 0.95). Copers and controls did not differ significantly. These findings suggest that inter-joint coordination and its variability during gait differ between copers and noncopers in males with ACLD and may have potential as a complementary clinical tool to inform neuromuscular retraining strategies prior to return to high-level activities.