Limb Symmetry Indexes Can Overestimate Knee Function After Anterior Cruciate Ligament Injury.
Elizabeth Wellsandt, Mathew J Failla, Lynn Snyder-Mackler
PMID 28355978WHAT IT FOUND
Limb symmetry tests overestimate knee recovery after ACL reconstruction.
More than half of patients who passed standard symmetry criteria failed to match their pre-injury baseline. Failing to restore this baseline function was linked to a higher risk of second ACL injuries.
Key findings
01Twenty-four patients who met the 90% limb symmetry index cut-off for strength and hop tests still failed to reach 90% of their pre-injury baseline capacity.
02Most patients who suffered a second ACL injury had previously passed standard limb symmetry criteria, but many of those had not restored their pre-injury baseline function.
03Using pre-injury baseline capacity to set return-to-sport criteria was more sensitive for predicting second injuries than using limb symmetry indexes.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was a secondary analysis of trial data, not a randomised test of the criteria themselves. The sample size for patients who suffered a second injury was small (11 patients), leading to wide confidence intervals. Pre-injury capacity was calculated retrospectively; it was not used to guide actual return-to-sport decisions during the study. There was significant attrition from the original cohort of 182 patients, with 32 excluded due to equipment changes. The study focused on athletes aged 14-55; results may not apply to older or less active populations.
Declared interests
The authors declared no financial affiliations or conflicts of interest.
The easy way to misread this
Do not conclude that pre-injury capacity testing is a validated, superior clinical standard yet. This was a small, secondary analysis where these metrics were not used to guide patient care, and the results for predicting re-injury had wide confidence intervals due to the low number of second injuries.