2025 ISAKOS Biennial Congress Paper
Knee Pathomechanics and Anterior Cruciate Ligament Anatomy of Females Compared to Males: In-Silico Analysis of 168 Matched Anterior Cruciate Ligament-Injured and Uninjured Individuals
Andrew Pechstein, PhD, New York UNITED STATES
Mitchell Wheatley, PhD, Long Island City, New York UNITED STATES
Mark Amirtharaj, MD, New York, NY UNITED STATES
David Shamritsky, MEng, New York, NY UNITED STATES
Michael Parides, PhD, New York, NY UNITED STATES
Carl W Imhauser, PhD, New York, NY UNITED STATES
Thomas L. Wickiewicz, MD, New York, NY UNITED STATES
Andrew D. Pearle, MD, New York, NY UNITED STATES
Bruce D. Beynnon, PhD, Burlington, VT UNITED STATES
Danyal H. Nawabi, MD, FRCS(Orth), New York, NY UNITED STATES
Hospital for Special Surgery, New York, New York, UNITED STATES
FDA Status Not Applicable
Summary
In computational knee models of 168 young, ACL-injured and uninjured athletes, ACL force under pivoting loads scaled by ACL cross-sectional area (CSA) (N/mm2) was 116% higher in injured females compared to healthy males; subgroup analysis showed geometry-driven ACL force was a key difference between injured and uninjured females and a combination of ACL force ACL CSA may be more critical in males.
Abstract
Background
Noncontact ACL injuries are common in young athletes, especially females. Multiple, sex-specific anatomic risk factors for ACL injury have been identified including lateral tibial slope, tibial spine geometry, and others. These geometric features influence tibiofemoral kinematics and ACL force. Also, ACL cross-sectional area (CSA) may influence ligament strength, and has been linked to injury risk. Unfortunately, the pathomechanics of male and female knees under pivoting loads are understudied and the role of both geometry-driven ACL force and ACL CSA is unclear. We developed computational models from a unique clinical data set to investigate how computational estimates of ACL force and measurements of ACL CSA combine to influence knee pathomechanics in young, male and female athletes.
Research Question: Does a combined measure of ACL force, as estimated under pivoting loads in computational models, scaled by subject-specific measures of ACL CSA differ between uninjured and injured male and female athletes?
Methods
With IRB approval we used MRI data from the uninjured knee of 168 high-school and college-athletes (120 females, 48 males), including cases with first-time noncontact ACL injury and uninjured controls matched 1:1 by sex, age, and sports team. We built computational knee models for each participant using 3D renderings of individuals’ tibiofemoral bone, articular cartilage, and meniscal geometries, then identified ligament attachments. Tissue stiffnesses and ligament slack-lengths were standardized. A pivoting load, including axial compression (100N), a valgus moment (8Nm), and an anterior force (30N) was applied sequentially to the tibia with the femur fixed at 15° flexion and the tibia free to move in all remaining directions. The model output was ACL force (N) at peak applied loads. ACL CSA was measured from uninjured-knee-MRI scans of participants at one-third the distance from the tibial to femoral insertion. ACL force was scaled by ACL CSA (N/mm2) and was evaluated between groups using one-way ANOVA with post-hoc pairwise-comparisons using a Bonferroni-Holm correction (α=0.05).
Results
ACL-injured females exhibited 116% greater ACL force scaled by ACL CSA compared to uninjured males (+1.9N/mm2, p<0.0001). ACL force scaled by ACL CSA was 59% greater in ACL-injured males compared to uninjured males (+1N/mm2, p=0.04) and was 35% greater in ACL-injured females compared to uninjured females (+0.9N/mm2, p=0.0015).
Discussion
ACL-injured females exhibited 2.2-fold greater ACL force scaled by ACL CSA than uninjured males, which highlights the large difference in non-modifiable-anatomy-induced ACL loading across the clinical spectrum from uninjured males to injured females. Scaling our estimates of ACL force by ACL CSA led to larger differentiation between injured and uninjured males (59% difference, p<0.0001) compared to ACL force alone (25% difference, +19N, p=0.196). This differentiation was greater for males than for females, where ACL force differed by 25% (+25N, p<0.003) and this difference among healthy and injured subjects only increased to 35% (p=0.0015) with scaling by ACL CSA. This indicates that knee geometries predisposing high ACL force may be a more dominant factor differentiating injured from healthy females whereas a combination of knee geometries and ACL CSA may be more critical in males.