Anterior Tibial Subluxation Across Knee Flexion Angles and Loading Conditions Is Greatest at Maximal Extension
Ryo Murakami, Shuji Taketomi, Kenichi Kono, Takashi Kobayashi, Takahiro Arakawa, Tomofumi Kage, Kohei Kawaguchi, Ryota Yamagami, Shoji Konda, Teruya Ishibashi, Takaharu Yamazaki, Sakae TanakaBackground:
Anterior tibial subluxation (ATS) is well-recognized as a clinically relevant marker of anterior cruciate ligament (ACL) deficiency and knee instability. However, ATS is assessed using various image modalities under different knee flexion angles and loading conditions, making interpretation and comparison across studies difficult.
Purpose/Hypothesis:
The purpose of this study was to examine the effects of knee flexion angle and weightbearing (WB) on ATS and to compare ATS between normal and ACL-deficient knees under WB and non-WB (NWB) conditions. The hypothesis of this study was that ATS varies according to knee flexion angle and loading condition and differs between normal and ACL-deficient knees.
Study Design:
Cross-sectional study; Level of evidence, 3.
Methods:
A total of 40 knees (20 normal, 20 ACL-deficient) were evaluated using fluoroscopic imaging during squatting (WB) and active assisted knee flexion (NWB). A 2-dimensional/3-dimensional registration technique was used to measure medial and lateral ATS values across knee flexion angles. A linear mixed-effects model was used to evaluate the effects of group (normal vs ACL-deficient), loading condition (WB vs NWB), and knee flexion angle.
Results:
Medial ATS was significantly greater in ACL-deficient knees than in normal knees across all flexion angles under both WB and NWB conditions (
Conclusion:
Both medial and lateral ATS change according to knee flexion angle and loading condition, with the greatest between-group differences observed at maximal knee extension, particularly in the medial compartment. Therefore, assessment at maximal knee extension may improve the detection of increased ATS in ACL-deficient knees and enhance clinical assessment.