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, 26 (5), 1406-1413

Kinematics and Arthrokinematics in the Chronic ACL-deficient Knee Are Altered Even in the Absence of Instability Symptoms

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Kinematics and Arthrokinematics in the Chronic ACL-deficient Knee Are Altered Even in the Absence of Instability Symptoms

Chen Yang et al. Knee Surg Sports Traumatol Arthrosc.

Abstract

Purpose: 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.

Methods: 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.

Results: Anterior-posterior translations were significantly larger in ACL-D than unaffected knees during level walking (all p < 0.001) and downhill running (all p ≤ 0.022). Internal rotation showed no significant difference between ACL-D and unaffected knees during level walking and downhill running. Closest contact points on the femur in ACL-D knees were consistently more anterior in the lateral compartment during downhill running (significant from 10 to 20% of the gait cycle, all p ≤ 0.044), but not during level walking. No differences in medial compartment contact paths were identified. Half of the participants had asymmetric K-L grades, with all having worse knee OA in the involved knee. Only 2 relatively young individuals had not progressed beyond stage 1 in either knee.

Conclusion: 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.

Level of evidence: Case-control study, Level III.

Keywords: Anterior cruciate ligament; Arthrokinematics; Biplane radiography; In vivo; Kinematics.

Conflict of interest statement

Conflict of interest The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
The model-based tracking process. Subject-specific CT-based bone models were matched to the biplane radiographs. Tracked motion of the femur and tibia bones was used to determine 3D kinematics of the tibiofemoral joint.
Fig. 2
Fig. 2
The center of closest subchondral bone contact point (black ball) and the migration of the closest contact point (white lines) on the medial and lateral femoral condyle.
Fig. 3
Fig. 3
Tibiofemoral anterior-posterior (AP) translation and internal/external (IE) rotation during walking and running in unaffected and ACL-deficient (ACL-D) knees. AP translations were significantly larger in ACL-D knees than unaffected knees during (a) level walking and (b) downhill running (* = p < 0.05). No differences between ACL-D and unaffected knees were identified in IE rotation during (c) level walking and (d) downhill running (n.s.). Error bars indicate inter-subject standard deviation. However, statistical tests were performed within-subjects (ACL-D vs. unaffected knees).
Fig. 4
Fig. 4
Ground reaction forces (GRFs) during (a) level walking and (b) downhill running. No significant differences between ACL-D and unaffected knees were identified.
Fig. 5
Fig. 5
Contact points (CPs) location in the anterior-posterior direction on the medial and lateral condyle during walking and running. No significant differences between ACL-D and unaffected knees were identified in the medial condyle during walking (a) or running (c), as well as the lateral condyle during walking (b). Contact points were more anterior in the lateral femoral condyle at specific instants of the running (d) cycle (* = p < 0.05).

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