Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes

Review written by Dr Travis Pollen info

Key Points

  1. The debate over whether pre-season screening tests like the vertical drop jump and single-leg squat are useful for identifying ACL injury risk has persisted for years.
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BACKGROUND & OBJECTIVE

The debate over whether screening tests are useful for identifying ACL injury risk has been raging for years. A 2005 study by Hewett et al. using 3D motion capture investigated whether knee abduction moment during a vertical drop jump could predict injury (1). The study found decent sensitivity and specificity for injury prediction (>70% each), but was limited by a relatively small sample. Conversely, a recent systematic review and meta-analysis concluded that knee abduction kinematics and kinetics may not be risk factors for ACL injury (2).

Due to the time, cost, and error associated with 3D motion capture, it has been proposed that two-dimensional video analysis of inward knee motion may be more valid and reliable than 3D techniques. Therefore, the purpose of this study was to determine whether there was an association between frontal plane inward knee motion (as measured from 2D video) and future non-contact ACL injury. In addition to the double-leg drop vertical jump, this study also included a single-leg squat test. The single-leg squat provides unique information about knee control compared to the drop vertical jump and, according to the authors, may better reflect the context of an ACL injury (3).

There is much debate over whether screening tests are useful for identifying ACL injury risk.
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Prospective research on single-leg drop vertical jumps and cutting maneuvers is crucial to furthering our understanding of the importance of inward knee motion.

METHODS

Over an 8-year period, the researchers screened 880 elite female handball and football athletes (21.5 ± 4 years old) in their pre-seasons and registered non-contact injuries twice yearly by contacting the athletes’ teams. Screening included two-dimensional video recordings of a

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