Related Experiment Video
Updated: Sep 11, 2026
Anterior Cruciate Ligament Transection and Synovial Fluid Lavage in a Rodent Model to Study Joint Inflammation and Posttraumatic Osteoarthritis
Published on: September 2, 2025
Alteration of Subchondral Bone Density Distribution Across the Knee Joint Before and After Anterior Cruciate Ligament
Taku Ebata1, Koji Iwasaki1,2, Dai Sato1
1Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan.
Background:
Anterior cruciate ligament (ACL) injury alters knee kinematics and contact mechanics, increasing posteromedial (PM) loading and the risk of knee osteoarthritis. Because subchondral bone density reflects long-term joint stress, its distribution may indicate chronic loading changes. Previous studies have shown higher proportions of high-density area (HDA%) in the PM tibial subchondral bone of ACL-injured knees than in healthy ones. However, it remains unclear whether ACL reconstruction restores normal tibial subchondral bone density distribution.
Purpose/Hypothesis:
The purpose of this study was to evaluate changes in tibial subchondral bone density after ACL reconstruction. It was hypothesized that reconstruction would reduce the elevated PM HDA% observed after injury.
Study Design:
Case series; Level of evidence, 4.
Methods:
Seventeen patients (7 men, 10 women) who underwent unilateral double-bundle ACL reconstruction were included. Computed tomography-osteoabsorptiometry (CT-OAM) was used to quantify the proportion of the proximal tibial surface occupied by HDA (top 20% of Hounsfield units) within 6 sagittal subregions: anteromedial (AM), centromedial (CM), PM, anterolateral, centrolateral, and posterolateral. The medial ratio represented the percentage of total tibial HDA in the medial compartment. Clinical assessments included side-to-side laxity, pivot-shift test, International Knee Documentation Committee score, Lysholm score, and Knee injury and Osteoarthritis Outcome Score (KOOS).
Results:
Anterior laxity improved from a mean of 3.3 mm (95% CI, 2.5 to 4.0 mm) to 0.4 mm (95% CI, -0.8 to 1.6 mm) postoperatively, and all pivot-shift tests were negative (P < .05). Clinical scores improved significantly. CT-OAM revealed decreased PM HDA% and increased CM HDA% (Holm-adjusted P = .003 and P = .011, respectively). The AM increase was nonsignificant after correction (P = .055). No significant lateral changes were noted. The medial ratio rose from 59.2% to 63.7% (P = .032) and correlated negatively with KOOS Sports (r = -0.561; P = .037).
Conclusion:
ACL reconstruction reduces PM overloading by decreasing PM HDA%, but the increased medial ratio suggests a shift of loading toward the medial compartment, which may relate to poorer sport-specific function.
