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. 2025 Jul 30:19417381251352524.
doi: 10.1177/19417381251352524. Online ahead of print.

Are Changes in Thigh Muscle Concentric Strength Associated With Changes in Leg Function After a Youth Sport-Related Knee Injury?

Justin M Losciale  1   2   3   4   5 , Christina Y Le  6   7 , Linda K Truong  1   2   8 , Garrett S Bullock  9   10 , Cameron J Mitchell  11 , Michael A Hunt  1   8 , Jackie L Whittaker  1   2   8
Affiliations

Are Changes in Thigh Muscle Concentric Strength Associated With Changes in Leg Function After a Youth Sport-Related Knee Injury?

Justin M Losciale et al. Sports Health. .

Abstract

Background: Assess the association between changes in injured leg knee extension and flexion strength (peak torque) and self-reported and performance-based measures of leg function after a variety of youth sport-related, time-loss knee injuries.

Hypothesis: There will be a relationship between changes in knee muscle strength and changes in measures of leg function in youth after a sport-related knee injury.

Study design: Prospective cohort study.

Level of evidence: Level 2.

Methods: This was a secondary analysis of the Alberta Youth Prevention of Early Osteoarthritis (PrEOA) Cohort study (Edmonton) that included youth (11-19 years old) who had experienced a medical attention, time-loss, sport-related knee injury in the previous 4 months. Injured leg knee extensor and flexor concentric peak torque (isokinetic; 90 deg/s), triple hop distance, modified Y-balance test (YBT), and Knee injury and Osteoarthritis Outcome Score Sport subscale (KOOSsport) were assessed at baseline (≤4 months postinjury) and 6 and 12 months later. Adjusted associations between 6- and 12-month change in strength and functional measures were assessed using multivariable regression (95% CI).

Results: Based on data from 106 participants (16.2 ± 1.8 years old), a 1 Nm increase in knee extensor strength (6-12 months) was associated with a 0.9 cm (95% CI, -0.5, 2.3) increase in hop distance. Similarly, every 1 Nm increase in knee flexor strength (6-12 months) was associated with a 0.3 cm (95% CI, -1.1, 1.7) increase in hop distance. Across other models, a 1 Nm increase in extensor or flexor strength was associated with a 0- to 0.3-point increase in KOOSsport score.

Conclusion: There was minimal-to-no longitudinal relationship between changes in knee extensor or flexor strength and changes in triple hop or YBT performance, or self-reported function within the first year after a youth sport-related knee injury.

Keywords: ACL; change over time; hop testing; muscle performance.

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Conflict of interest statement

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was funded by The Arthritis Society Young Investigator Operating Grant (Whittaker YIO-16-379). J.M.L. was funded by the Arthritis Society PhD Salary Award (21-0000000086) and the University of British Columbia 4-year fellowship. J.L.W. is supported by a Michael Smith Foundation for Health Research a Scholar Award (SCH-2020-0403). The funders played no role in the design, conduct, or reporting of this study.

The authors report no potential conflicts of interest in the development and publication of this article.

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