To analyze the in vivo kinematics and arthrokinematics of chronic ACL-deficient (ACL-D) and unaffected contralateral knees during level walking and downhill running using dynamic biplane radiography. It was hypothesized that ACL-D knees would demonstrate increased anterior translation and internal rotation, and that ACL-deficiency would alter the tibiofemoral contact paths in comparison to the unaffected contralateral side.
Eight participants with unilateral chronic ACL-D without instability symptoms were recruited. The contralateral unaffected knee was considered as control. Kellgren-Lawrence (K-L) grades were determined from ACL-D and unaffected knees. Dynamic knee motion was determined from footstrike through the early-stance phase (20-25% of gait cycle) using a validated volumetric model-based tracking process that matched subject-specific CT bone models to dynamic biplane radiographs. Participants performed level walking at 1.2 m/s and downhill running at 2.5 m/s while biplane radiographs were collected at 100 and 150 images per second, respectively. Tibiofemoral kinematics and arthrokinematics (the path of the closest contact point between articulating subchondral bone surfaces) were determined and compared between ACL-D and unaffected knees. A two-way repeated measures analysis of variance was used to identify differences between ACL-D and unaffected knees at 5% increments of the gait cycle.
Anterior-posterior translations were significantly larger in ACL-D than unaffected knees during level walking (all p < 0.001) and downhill running (all p ae
The results suggest that anterior translation and knee joint contact paths are altered in ACL-D knees even in the absence of instability symptoms. The clinical relevance is that ACL-D patients who do not report symptoms of instability likely still demonstrate altered knee kinematics and arthrokinematics compared to their uninvolved limb.
Case-control study, Level III.