Clinical impact of normative data in ankle strength evaluation

Abstract

This letter offers a critical perspective on the recent work by da Fonseca et al, a study that finally provides a much-needed set of normative isokinetic data for the ankle in healthy, non-athletic adults. The authors meticulously map out gender-specific torque profiles and agonist-antagonist balances, but their most compelling finding, in my view, is the empirical validation of a > 90% symmetry threshold for both the limb symmetry index and a novel muscular deficiency index. This result provides a solid, evidence-based anchor for ankle rehabilitation, a field that has long operated in the shadow of its more thoroughly researched counterpart, the knee. I argue that this study’s chief contribution is its clear challenge to the long-standing clinical reliance on the contralateral limb as a recovery benchmark - a practice complicated by the presence of bilateral deficits. By avoiding repeated emphasis on this issue, the letter now highlights this point more succinctly. While acknowledging the study’s cross-sectional nature as a limitation, I contend that these normative values represent a fundamental step toward more objective, reliable, and ultimately safer return-to-activity decisions.

Keywords: Ankle isokinetic; Normative data; Limb symmetry index; Return-to-sport criteria; Neuromuscular deficits

Core Tip: The work by da Fonseca et al provides a crucial, long-awaited normative dataset for isokinetic ankle strength. What’s particularly striking is their finding that healthy ankles naturally exhibit over 90% bilateral symmetry, as measured by both limb symmetry index and their new muscular deficiency index. This empirically grounds the > 90% threshold, a standard borrowed from knee rehabilitation, as a valid and achievable goal for the ankle. The clinical takeaway is clear: We now have objective, gender-specific benchmarks that allow us to move beyond the flawed assumption that the uninjured limb is a perfect ‘control’. This research equips clinicians with the tools to make more precise and defensible decisions about rehabilitation progress and safe return to activity.