2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


Assessment of Knee Function Using Inertial Measurement Units in Anterior Cruciate Ligament Reconstructed Individuals

Timothy S. Whitehead, MBBS, FRACS, Richmond, VIC AUSTRALIA
Argell San Jose, PhD, Richmond, Victoria AUSTRALIA
Pei-Wei Chi, PhD, Richmond, Victoria AUSTRALIA
Emma Rosario, ExSc, Richmond, Victoria AUSTRALIA
Rebecca Cordingley, PhD, Richmond, Victoria AUSTRALIA

OrthoSport Victoria Institute, Richmond, Victoria, AUSTRALIA

FDA Status Not Applicable

Summary

Knee function assessed with IMU's following ACLR, demonstrates biomehanical asymmetries in a patient cohort cleared to return to sport on triple hop for distance LSI.

Abstract

Introduction

Limb symmetry index (LSI) in triple forward hopping (3-Hop) distance is a commonly used criteria for return-to-sports (RTS) clearance following anterior cruciate ligament reconstruction (ACLR) [1]. Recent 3-dimensional (3D) biomechanical studies using marker-based camera system have shown that 3-Hop distance LSI could potentially mask lingering deficits in knee function after ACLR [2]. This demonstrates the importance of using 3D biomechanical analysis to assess recovery of knee function following ACLR. However, marker-based camera assessment is limited to specialized research laboratories that may not be easily accessible to ACLR patients. The emergence of inertial measurement unit (IMU) based systems could be a more practical solution for biomechanical assessment in clinical settings. To date, there is limited evidence on the use of IMUs to assess knee function in the clinical setting following ACLR. The aim of this study was to investigate IMU-derived knee joint kinematics during 3-Hop tasks in ACLR individuals who meet common return to sports (RTS) clearance criteria (i.e., hop distance LSI >90).

Methods

79 patients (Male = 51 and Female = 28; between 6 to 12 months post-ACLR) who had a 3-Hop distance LSI >90 were recruited for this study. The total hop distance and knee joint kinematics (°) during the ground contact phases of 3-Hop tasks were assessed via 8 IMUs (Xsens MVN system). The percentage of the ALCR leg divided by the contralateral leg was used to calculate hop distance LSI (%). Mixed effects model with random effects for participants, was performed to assess differences in joint kinematics (p < 0.05)

Results

The average 3-Hop distance LSI for all participants was 99.4±6.7%. Kinematic analysis showed less knee flexion angle at initial contact (2.5 and 2.1°; p < 0.001), less peak knee flexion angle (3.1 and 3.6°; p < 0.001), and less knee flexion excursion (3.3 and 4.0°; p < 0.001) in the ACLR leg compared to the contralateral leg during the first and second ground contact phases of 3-Hop tasks.

Discussion

Despite achieving 3-Hop distance symmetry, IMU-based kinematic analysis of the knee shows a “stiffer” landing pattern in the ACLR compared to the contralateral leg. Given the importance of identifying movement mechanics following ACLR, these findings show the potential utility of using IMU-based biomechanical outcome measures to assess knee function, and further improve RTS criteria following ACLR.
Clinical implication: Using clinically accessible IMUs could be an alternative to traditional laboratory-based motion capture systems for assessment of knee function after ACLR in the clinical setting.