Critical Analysis of Limb Symmetry Indices of Hop Tests in Athletes After
Anterior Cruciate Ligament Reconstruction: A Case Control Study

A, Welling W, Benjaminse A, Lemmink K, Seil R, & Zaffagnini S. Orthopaedics and Traumatology: Surgery and
2017; Published online ahead of print


Take Home Message: Athletes after an anterior cruciate
ligament (ACL) reconstruction perform poorly bilaterally in hop testing when
compared with healthy matched controls. 

We have recently had a few posts on Sports Med Res investigating return to
play testing after anterior cruciate ligament (ACL) reconstructive surgery (see
below).  Oftentimes, the surgical side is
compared to the nonsurgical side in regard to strength, function, and range of
motion.  Many clinicians are increasingly
using a series of single-limb hop tests as functional assessments. However, the
contralateral limb may be an inappropriate comparison if it is also weak or
functioning at suboptimal levels.  The
authors of this
case-control study compared both limbs of athletes with a previous history of an
isolated ACL reconstruction to control athletes on hop test performance.  Fifty-two athletes performed a single-leg
hop, a triple hop, and a side hop at an average of 7 months post-surgery. These
results were compared to healthy athletes. 
The authors compared the involved to the uninvolved limb of the ACL
reconstructed participants (limb symmetry index) and found that a little over
80% were ≥ 90% in comparison to their healthy limb, with an average limb
symmetry index of 95% on the 3 hop tests. 
On average, athletes after an ACL reconstruction hopped shorter
distances with both limbs compared with healthy control data for single-leg-hop
and triple-hop tests.  Males who had an ACL
reconstruction also performed worse on the side hop compared with healthy

These authors found that despite most
ACL reconstructed participants having an acceptable limb symmetry index (>
90%), they still had impaired performance compared with matched healthy
participants.  Therefore, it remains
questionable as to whether the uninvolved limb is an appropriate comparison at
around 7 months post-surgery.  However,
this should be interpreted with caution because the control normative data was
collected by other authors at an earlier date, and this may cause variations and
is a limitation of the comparison.  It
would be interesting to see how the results would compare if the uninvolved
limb was tested shortly after injury.  There
was another
recent post which used strength testing of the uninvolved limb shortly
after the time of injury and found this to be a better comparison for achieving
post-surgical gains.  The authors also
introduced a side hop test, which is less commonly used.  They reported that ACL reconstructed males
performed poorly compared with healthy controls.  However, it would be interesting to see if
you could incorporate an assessment of the quality of the side hop (e.g.,
looking for valgus collapse), specifically in the female participants.  As clinicians, we should remember that there
is a deconditioning that happens bilaterally after a surgical procedure.  This study offers more evidence to support
that it might be inappropriate to compare the involved limb to the uninvolved
limb at the time of post-operative testing (7 months post-surgery in this
case).  Baseline testing, normative data,
or uninvolved performance close to the time of injury may be best for

for Discussion:  When do you assess
uninvolved strength or function in an ACL case? 
Are there other hop tests that you utilize for making return to play
by: Nicole Cattano
by: Jeffrey Driban


Variability in Leg Muscle Power and Hop Performance After ACL Reconstruction

Gokeler, A., Welling, W., Benjaminse, A., Lemmink, K., Seil, R., & Zaffagnini, S. (2017). A Critical Analysis of Limb Symmetry Indices of Hop Tests in Athletes After Anterior Cruciate Ligament Reconstruction: A Case Control Study Orthopaedics & Traumatology: Surgery & Research DOI: 10.1016/j.otsr.2017.02.015