The influence of task complexity on knee joint kinetics following ACL reconstruction.
BACKGROUND
Previous research indicates that subjects with anterior cruciate ligament reconstruction exhibit abnormal knee joint movement patterns during functional activities like walking. While the sagittal plane mechanics have been studied extensively, less is known about the secondary planes, specifically with regard to more demanding tasks. This study explored the influence of task complexity on functional joint mechanics in the context of graft-specific surgeries.


METHODS
In 25 participants (10 hamstring tendon graft, 6 patellar tendon graft, 9 matched controls), three-dimensional joint torques were calculated using a standard inverse dynamics approach during level walking and stair descent. The stair descent task was separated into two functionally different sub-tasks-step-to-floor and step-to-step. The differences in external knee moment profiles were compared between groups; paired differences between the reconstructed and non-reconstructed knees were also assessed.


FINDINGS
The reconstructed knees, irrespective of graft type, typically exhibited significantly lower peak knee flexion moments compared to control knees during stair descent, with the differences more pronounced in the step-to-step task. Frontal plane adduction torque deficits were graft specific and limited to the hamstring tendon knees during the step-to-step task. Internal rotation torque deficits were also primarily limited to the hamstring tendon graft group during stair descent. Collectively, these results suggest that task complexity was a primary driver of differences in joint mechanics between anterior cruciate ligament reconstructed individuals and controls, and such differences were more pronounced in individuals with hamstring tendon grafts.


INTERPRETATION
The mechanical environment experienced in the cartilage during repetitive, cyclical tasks such as walking and other activities of daily living has been argued to contribute to the development of degenerative changes to the joint and ultimately osteoarthritis. Given the task-specific and graft-specific differences in joint mechanics detected in this study, care should be taken during the rehabilitation process to mitigate these changes.
['Schroeder|Megan J|MJ|', 'Krishnan|Chandramouli|C|', 'Dhaher|Yasin Y|YY|']
D000203:Activities of Daily Living D000328:Adult D000070598:Anterior Cruciate Ligament Injuries D059549:Anterior Cruciate Ligament Reconstruction D001696:Biomechanical Phenomena D005260:Female D005684:Gait D006801:Humans D007719:Knee Joint D008297:Male D018482:Muscle, Skeletal D010329:Patella D017847:Patellar Ligament D011795:Surveys and Questionnaires D013710:Tendons D019415:Torque D016138:Walking
Knee ACL reconstruction Joint torques Stair descent Gait Motion analysis