Thigh muscle co-activation during a single leg hop for distance one year after ACL-reconstruction and its relationship with a 2D knee flexion score: a cross-sectional study.
- 1Department of Health Professions, Physiotherapy, Bern University of Applied Sciences, Murtenstrasse 10, Bern, CH-3008, Switzerland. [email protected].
- 2Department of Health Professions, Physiotherapy, Bern University of Applied Sciences, Murtenstrasse 10, Bern, CH-3008, Switzerland.
Abstract
Background
Landing alterations during single leg hop to distance (SLHD) testing persist after anterior cruciate ligament (ACL) reconstruction and may contribute to a high risk of re-injury. Increased thigh muscle co-activation is recognised as a common neuromuscular adaptation after ACL injury, but conflicting results have been reported for jump landings. Therefore, this study aimed to assess changes in co-activation at one year post-reconstruction during the landing of a SLHD and to evaluate whether a 2D knee flexion scoring system could identify landings with heightened co-activation.Method
This cross-sectional study assessed 18 sportingly active individuals one year after ACL-reconstruction alongside 18 matched control participants. Co-activation of the quadriceps and hamstring musculature during landing was recorded via electromyography. Additionally, peak knee flexion was assessed and scored as < 60°, between 60° and 80 ° and > 80° with a clinically practical 2D analysis. Co-activation was compared between the ACL-reconstructed leg, the contralateral leg and the matched control leg as well as between 2D-scored trials with statistical parameter mapping (SPM).Results
SPM analysis revealed greater thigh muscle co-activation in ACL-reconstructed leg compared to the matched control leg from 229 ms to 250 ms after initial contact (p = 0.007). No significant differences were observed between the ACL-reconstructed and contralateral leg. 2D knee flexion scoring did not reveal differences in co-activation during landing.Conclusion
Neuromuscular control is not fully restored at one year post-ACL-reconstruction, and consideration of thigh muscle co-activation during single leg hop testing could be important. However, a 2D knee flexion scoring system is not suitable for revealing co-activation differences among recreational sportingly active people, and alternative methods are needed to assess these neuromuscular adaptations in the clinic.Trial registration
The study was pre-registered at the German Clinical Trials Register (DRKS-ID: 00023002).
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BibTeX
@article{probst2026thigh,
title = {{Thigh muscle co-activation during a single leg hop for distance one year after ACL-reconstruction and its relationship with a 2D knee flexion score: a cross-sectional study.}},
author = {Jano Probst and Patric Eichelberger and Aglaja Busch},
journal = {BMC musculoskeletal disorders},
year = {2026},
month = jul,
doi = {10.1186/s12891-026-10236-x},
url = {https://europepmc.org/article/MED/42963538},
note = {CC BY},
}
RIS
TY - JOUR
TI - Thigh muscle co-activation during a single leg hop for distance one year after ACL-reconstruction and its relationship with a 2D knee flexion score: a cross-sectional study.
AU - Jano Probst
AU - Patric Eichelberger
AU - Aglaja Busch
PY - 2026
DA - 2026/07/30
JO - BMC musculoskeletal disorders
DO - 10.1186/s12891-026-10236-x
UR - https://europepmc.org/article/MED/42963538
AB - Background Landing alterations during single leg hop to distance (SLHD) testing persist after anterior cruciate ligament (ACL) reconstruction and may contribute to a high risk of re-injury. Increased thigh muscle co-activation is recognised as a common neuromuscular adaptation after ACL injury, but conflicting results have been reported for jump landings. Therefore, this study aimed to assess changes in co-activation at one year post-reconstruction during the landing of a SLHD and to evaluate whether a 2D knee flexion scoring system could identify landings with heightened co-activation.Method This cross-sectional study assessed 18 sportingly active individuals one year after ACL-reconstruction alongside 18 matched control participants. Co-activation of the quadriceps and hamstring musculature during landing was recorded via electromyography. Additionally, peak knee flexion was assessed and scored as < 60°, between 60° and 80 ° and > 80° with a clinically practical 2D analysis. Co-activation was compared between the ACL-reconstructed leg, the contralateral leg and the matched control leg as well as between 2D-scored trials with statistical parameter mapping (SPM).Results SPM analysis revealed greater thigh muscle co-activation in ACL-reconstructed leg compared to the matched control leg from 229 ms to 250 ms after initial contact (p = 0.007). No significant differences were observed between the ACL-reconstructed and contralateral leg. 2D knee flexion scoring did not reveal differences in co-activation during landing.Conclusion Neuromuscular control is not fully restored at one year post-ACL-reconstruction, and consideration of thigh muscle co-activation during single leg hop testing could be important. However, a 2D knee flexion scoring system is not suitable for revealing co-activation differences among recreational sportingly active people, and alternative methods are needed to assess these neuromuscular adaptations in the clinic.Trial registration The study was pre-registered at the German Clinical Trials Register (DRKS-ID: 00023002).
SN - 1471-2474
ER -