Which assessments are used to analyze neuromuscular control by electromyography after an anterior cruciate ligament injury to determine readiness to return to sports? A systematic review

Abstract
Background: Adequate neuromuscular control of the knee could be one element to prevent secondary injuries after
an anterior cruciate ligament (ACL) injury. To assess neuromuscular control in terms of time, amplitude and activity,
electromyography (EMG) is used. However, it is unclear which assessments using EMG could be used for a safe return
to sports (RTS). Therefore, we aimed to summarize EMG-related assessments for neuromuscular control of the knee in
adult patients after an ACL injury to decide upon readiness for RTS.
Methods: This systematic review followed guidelines of Preferred Reporting of Items for Systematic Reviews and
Meta-Analyses (PRISMA) and Cochrane recommendations. MEDLINE/PubMed, EMBASE, CINAHL, Cochrane Library,
Physiotherapy Evidence Database (PEDro), SPORTDiscus and the Web of Science were searched from inception to
March 2019 and updated in November 2020. Studies identifying electromyographic assessments for neuromuscular
control during dynamic tasks in adult, physically active patients with an anterior cruciate ligament injury were eligible
and qualitatively synthesized. Two independent reviewers used a modifed Downs and Black checklist to assess risk of
bias of included studies.
Results: From initially 1388 hits, 38 mainly cross-sectional, case-controlled studies were included for qualitative analysis. Most studies provided EMG outcomes of thigh muscles during jumping, running or squatting. Outcomes measures described neuromuscular control of the knee in domains of time, amplitude or activity. Risk of bias was medium
to high due to an unclear description of participants and prior interventions, confounding factors and incompletely
reported results.
Conclusions: Despite a wide range of EMG outcome measures for neuromuscular control, none was used to decide
upon return to sports in these patients. Additional studies are needed to defne readiness towards RTS by assessing neuromuscular control in adult ACL patients with EMG. Further research should aim at fnding reliable and valid,
EMG-related variables to be used as diagnostic tool for neuromuscular control. Moreover, future studies should aim at more homogenous groups including adequately matched healthy subjects, evaluate gender separately and use
sport-specifc tasks.
Registration The protocol for this systematic review was indexed beforehand in the International Prospective Register
of Systematic Reviews (PROSPERO) and registered as CRD42019122188.
Keywords: Knee, Anterior cruciate ligament injuries, ACL, Electromyography, EMG, Rehabilitation, Patient outcome
assessment, Neuromuscular control, Return to sports, RTS