Motor Learning of Knee Joint Kinematics in Patients Within the First Year After ACL Reconstruction

Undergoing anterior cruciate ligament (ACL) reconstruction (ACLR) does not normalize the asymmetric knee biomechanics during gait that are related to the later development of post-traumatic osteoarthritis. ACL rupture and reconstruction have negative neuromuscular implications, disrupting knee joint afferent inputs that may be essential for central nervous system adaptability and motor learning. Here, we examined the ability of patients after ACLR to adapt knee joint biomechanics using a split-belt treadmill locomotor learning paradigm compared with uninjured controls.

Patients after ACLR will be able to adapt and retain their knee joint mechanics, but to a lesser extent than controls.

Cross-sectional study.

Level III.

We examined neuromuscular adaptations (ie, motor learning) using an evidence-based split-belt treadmill adaptation paradigm in 15 patients (20.8 ± 3.5 years old, 9 female), 3 to 9 months after ACLR and 15 control patients. During adaptation, the 2 treadmill belts were split (ie, moving at different speeds) to induce motor learning of new knee joint kinematic patterns. Three-dimensional motion capture was used to record joint kinematics and assess adaptation of knee flexion and extension angles. We also measured quadriceps strength, knee joint proprioception, and other markers of ACLR recovery.

After ACLR, patients showed flexibility in motor patterns for peak knee flexion and extension angles. Our data showed no difference between patients after ACLR and uninjured controls in the extent of adaptation of either kinematic variable.

These data suggest that knee kinematics are malleable during rehabilitation, and demonstrate adaptability in the nervous system for knee joint angles during gait.

Current clinical interventions and evidence-based rehabilitation programs have not been successful in restoring gait mechanics. The current work indicates motor learning-based approaches can modify knee joint kinematics and therefore may be worthy of consideration in future interventions to address poor gait mechanics after ACLR.