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©The Author(s) 2025. Published by Baishideng Publishing Group Inc. All rights reserved.
Normative values of ankle strength and its importance for rehabilitation and return to activity: A cross-sectional study
Lucas Furtado da Fonseca, Madhan Jeyaraman, Naveen Jeyaraman, Thiago Resende Inojossa, Eduardo Souza Maciel, Cesar de Cesar Netto, Nacime Salomão Mansur, Diego Costa Astur
Lucas Furtado da Fonseca, Eduardo Souza Maciel, Diego Costa Astur, Department of Orthopaedics and Traumatology, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo 04024-900, Brazil
Madhan Jeyaraman, Naveen Jeyaraman, Department of Orthopaedics, ACS Medical College and Hospital, Dr MGR Educational and Research Institute, Chennai 600077, Tamil Nadu, India
Madhan Jeyaraman, Naveen Jeyaraman, Department of Regenerative Medicine, Agathisha Institute of Stemcell and Regenerative Medicine (AISRM), Chennai 600030, Tamil Nadu, India
Thiago Resende Inojossa, Rehabilitation Sector, Hcor Heart Hospital, São Paulo 04003-905, Brazil
Cesar de Cesar Netto, Nacime Salomão Mansur, Department of Orthopedic Surgery, Duke University, Durham, NC 27710, United States
Co-corresponding authors: Lucas Furtado da Fonseca and Madhan Jeyaraman.
Author contributions: Da Fonseca LF contributed to conceptualization; da Fonseca LF, Maciel ES, Netto CC, Mansur NS, and Astur DC contributed to acquiring clinical data and performing the data analysis; da Fonseca LF, Jeyaraman M, and Jeyaraman N contributed to manuscript writing; Inojossa TR helped in manuscript revision; da Fonseca LF contributed for image acquisition; Jeyaraman M contributed to proofreading; da Fonseca LF and Jeyaraman M contributed to administration. da Fonseca LF and Jeyaraman M have played an important and indispensable roles in the experimental design, data interpretation and manuscript preparation as the co-corresponding authors. All authors have agreed to the final version to be published and agree to be accountable for all aspects of the work.
Institutional review board statement: The study protocol was approved by the Ethics Committee of the Federal University of São Paulo (No. 3.696.560).
Informed consent statement: Obtained from all participants of the study.
Conflict-of-interest statement: All authors declare no conflicts of interest in publishing the manuscript.
STROBE statement: The authors have read the STROBE Statement – checklist of items, and the manuscript was prepared and revised according to the STROBE Statement – checklist of items.
Data sharing statement: Data is contained within the manuscript.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
https://creativecommons.org/Licenses/by-nc/4.0/ Corresponding author: Lucas Furtado da Fonseca, MD, Associate Professor, Researcher, Department of Orthopaedics and Traumatology, Paulista School of Medicine, Federal University of Sao Paulo, R. Sena Madureira, 1500 - Vila Clementino, Sao Paulo 04024-900, Brazil.
contato@drlucasfonseca.med.br
Received: April 25, 2025
Revised: May 28, 2025
Accepted: August 28, 2025
Published online: October 18, 2025
Processing time: 175 Days and 4.7 Hours
BACKGROUND
Ankle normative values are limited compared to isokinetic knee assessments. Chronic ankle instability correlates with agonist-antagonist imbalances, decreased evertor/invertor ratio, and plantar flexion deficits. Strengthening programs targeting evertor/invertor and dorsiflexor/plantar flexor balance help reduce injury recurrence. Bilateral neuromuscular deficits compromise the contralateral side, rendering healthy limbs unsuitable as recovery references. Defining normative healthy ankle parameters is crucial for establishing precise limits in non-surgical treatments and sports return criteria. While the limb symmetry index (LSI) is used for knees with a cutoff of > 90%, no such standardization exists for the ankle.
AIM
To comprehensively evaluate isokinetic ankle strength profiles in non-athletic individuals.
METHODS
This is a cross-sectional study. Two hundred ankles were evaluated using the Biodex 3 System to assess eversion, inversion, dorsiflexion, and plantar flexion. Healthy individuals with an active lifestyle and no previous injuries were evaluated. The Maximum Torque, Agonist/Antagonist Ratio, LSI, and Muscular Deficiency Index (MDI) and the correlation with demographic variables were evaluated.
RESULTS
The mean age (mean ± SD) was 38.5 ± 13.5 years, and the body mass index (BMI) was 25.8 ± 4.2 in 69 men and 31 women. The mean maximum torque values by gender were (mean ± SD): 22.3 ± 6.6 female (F) and 33.4 ± 9.9 male (M) N/m for eversion; 30.10 ± 10.0 (F) and 37.0 ± 11.6 N/m (M) for inversion, 37.4 ± 10.0 (F) and 53.6 ± 13.0 N/m (M) for dorsiflexion, and 100.4 ± 37.2 (F) and 158.1 ± 33.4 (M) N/m for flexion. There was no correlation between age or BMI and maximum torque. The evertors/invertors ratio was 88.8%, and the dorsiflexors/plantar flexors ratio was 36.1%. The MDI and LSI were balanced between sides for every movement, having an average global difference of less than 10%.
CONCLUSION
These findings provide gender-specific normative isokinetic values for the ankle in healthy, physically active adults. These reference parameters—especially LSI and MDI above 90%—can support clinical decision-making in rehabilitation planning and return-to-sport assessment, offering objective benchmarks for functional recovery.
Core Tip: Normative isokinetic strength values for non-athletic ankles serve as essential benchmarks for guiding rehabilitation and return-to-sport criteria. The findings reveal notable gender-based differences in maximum torque values, while showing no significant correlation with age or body mass index. Balanced Limb Symmetry Index and Muscular Deficiency Index across movements highlight the importance of standardization. These outcomes offer a robust framework for refining non-surgical treatments, developing targeted strength restoration programs, and reducing the risk of recurring injuries.
