Neuromuscular Profiles After Anterior Cruciate Ligament Reconstruction

Exploratory Study of Neuromuscular Profiles After Anterior Cruciate Ligament Reconstruction in Clinical Conditions: Combined Analysis of Isokinetic Strength and Surface Electromyography

The NEURO-ACL-ISOEMG study is an observational, cross-sectional, exploratory study conducted in patients between 4 and 12 months after anterior cruciate ligament (ACL) reconstruction.

The primary objective is to describe the joint distribution of isokinetic muscle strength and surface electromyographic (sEMG) activation parameters of the quadriceps and hamstrings in order to explore different neuromuscular profiles under clinical conditions.

The study combines data from the routine functional assessment, including isokinetic strength measurements and a single-leg hop test, with surface electromyography and patient-reported questionnaires assessing knee self-efficacy, kinesiophobia, symptoms, and knee function.

Persistent muscle strength deficits are frequently observed after anterior cruciate ligament (ACL) reconstruction and may be related to both peripheral muscular factors and alterations in neuromuscular activation. However, few studies have simultaneously assessed isokinetic strength and electromyographic activation of both agonist and antagonist muscles under analytical and functional conditions.

NEURO-ACL-ISOEMG is a monocentric, observational, cross-sectional, exploratory study designed to characterize neuromuscular profiles in patients evaluated between 4 and 12 months after ACL reconstruction.

The primary objective is to describe the joint distribution of isokinetic muscle strength and surface electromyographic activation parameters of the quadriceps and hamstrings. Isokinetic assessment includes quadriceps and hamstring peak torque and the Limb Symmetry Index (LSI). Surface electromyography is used to assess activation of the vastus medialis, vastus lateralis, semitendinosus, and biceps femoris during standardized isometric contractions.

Secondary objectives include describing electromyographic patterns during a single-leg functional task, exploring the concordance between electromyographic parameters obtained under analytical and functional conditions, describing the distribution of patients according to different combinations of isokinetic strength and electromyographic activation, and exploring associations between neuromuscular profiles, functional performance, and psychological factors. The study also assesses the completeness and usability of data obtained from the functional assessment in routine clinical practice.

Participants undergo a single study visit during their routine functional assessment after ACL reconstruction. Routine assessment includes isokinetic strength measurements and a single-leg hop test. For the purposes of the study, surface electromyography and three patient-reported questionnaires are added: the Knee Self-Efficacy Scale (K-SES), the Tampa Scale for Kinesiophobia (TSK), and the International Knee Documentation Committee (IKDC) questionnaire.

The study does not modify the participants' therapeutic management and is not intended to establish an individual diagnosis. Its purpose is to provide an exploratory characterization of the heterogeneity of neuromuscular recovery after ACL reconstruction and to generate hypotheses that may contribute to the interpretation of functional assessments and future rehabilitation strategies.

Inclusion Criteria:

• Anterior cruciate ligament (ACL) reconstruction.
• Postoperative period between 4 and 12 months.
• Age 18 years or older.
• Affiliation with or beneficiary of a social security scheme.
• Ability to understand the study information and to express non-opposition to participation.

Exclusion Criteria:

• Persons under guardianship, curatorship, or another legal protection measure.
• Any condition preventing safe performance of isokinetic testing, including significant pain, significant joint effusion, substantial limitation of joint range of motion, clinical knee instability, or an ongoing postoperative complication.
• Opposition to participation in the study.