Which assessments are used to analyze active knee stability after an anterior cruciate ligament injury to determine readiness to return to sports

Background Adequate neuromuscular control of the knee for active joint stability could be one element to prevent secondary injuries after an anterior cruciate ligament (ACL) injury, either treated conservatively or surgically. However, it is unclear which measurements should be used to assess neuromuscular control of the knee for a safe return to sports (RTS). Purpose To summarize assessments for neuromuscular control of the knee in athletes after an ACL injury to decide upon readiness towards a successful return to sports (RTS). Study design Systematic review, level of evidence 4 Methods This systematic review followed the guidelines of Preferred Reporting of Items for Systematic Reviews and Meta-analyses (PRISMA) and has been listed in PROSPERO (CRD42019122188). The databases MEDLINE/PubMed, EMBASE, CINAHL, Cochrane Library, Physiotherapy Evidence Database (PEDro), SPORTDiscus and the Web of Science were searched from inception until March 2019. The search was updated with e-mail alerts from the searched databases until December 2019 and yielded to studies identifying assessments using electromyography (EMG) for neuromuscular control during dynamic activities in patients with an ACL rupture or repair. All included articles were assessed for risk of bias with a modified Downs and Black checklist. Results A total of 1178 records were identified through database search. After screening for title, abstract and content regarding in- and exclusion criteria, 31 articles could be included for analysis. Another six articles could be included from hand search of reference lists of the included articles, resulting in a total of 37 articles. Surface EMG was used in all studies as method to assess neuromuscular control. However, there was a wide range of tasks, interventions, muscles measured, and outcomes used. 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 a safe RTS in adult patients after an ACL injury. Clinical relevance Future studies should aim at finding valid and reliable assessments for neuromuscular control to judge upon readiness towards RTS. Key words: anterior cruciate ligament, assessment, active knee stability, neuromuscular control, return to sports