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Additional perspectives on ‘ACL rupture is a single leg injury but a double leg problem…’
  1. Anna Trulsson1,2
  1. 1 Department of Pain Rehabilitation, Skåne University Hospital, Lund, Sweden
  2. 2 Department of Health Sciences, Physiotherapy, Lund University, Lund, Sweden
  1. Correspondence to Dr Anna Trulsson, Department of Pain Rehabilitation, Skåne University Hospital, S-22185 Lund, Sweden ; anna.trulsson{at}

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Additional perspectives on Commentary bjsports-2017-098502: ‘ACL rupture is a single leg injury but a double leg problem: too much focus on “symmetry” alone and that’s not enough!’1

In the Commentary ‘ACL rupture is a single leg injury but a double leg problem…’, the authors argue that measurements of limb symmetry underestimate deficits. I mainly agree with the authors, but reason for when and how symmetry measurements should be used and also for the use of versatile test batteries. To choose adequate functional tests in the clinic and to design new test-batteries and rehabilitation programmes for individuals with ACL injury, I propose to look for answers and solutions in the extensive literature on motor control. Therefore, basics of motor control are recapitulated.

Limb Symmetry Index (LSI) is not perfect but can be relevant: when and how?

No consensus exists on how to decide when to return to sports.2 Often, strength and hop tests are used, calculating an LSI (the ratio of injured/non-injured sides), and LSI >90% is frequently suggested as a cut-off criteria.3 However, individuals with ACL reconstruction rarely reach 90% symmetry.4 Moreover, impaired capacity on both sides after ACL injury is well known, underestimating deficits measured as LSI. Therefore, measurements of preinjury capacity or normative data of non-injured controls have been suggested, since they may be more sensitive in predicting second ACL injuries.5 Therefore, to meet the concerns of the double leg problem I argue for that when LSI is used, it should be interpreted in combination with applicable normative data of controls or …

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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Commissioned; externally peer reviewed.

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