Helbing’s or Helbing Sign is the medial bowing of Achilles tendon observed from behind when someone is standing in their relaxed calcaneal stance position. It was traditionally assumed to indicate an excessively pronated or flat foot. It was initially described by German physician, Carl Helbing (1842-1914) in 1905 in a paper titled Ueber metatarsus varus.
Helbing’s sign is observed as the ‘C’ shaped, medially oriented curvature or bowing of the Tendo Achilles in the frontal plane associated with an everted or compensated valgus position of the posterior aspect of the calcaneus. However, if the individual has a rearfoot varus or an inverted position of the calcaneus when the subtalar joint is in it neutral subtalar joint position, they will have a more vertical position of the calcaneus on relaxed weightbearing, so despite having significant pronation or eversion at the subtalar joint to get to that more vertical position, Helbing’s sign will not be present (ie the Achilles tendon will be straight). This limits the usefulness of the Helbing sign as it will only be present when the calcaneus everts past vertical.
Helbing’s sign is a frontal plane observation of static foot posture and does not necessarily have a relationship to sagittal plane (eg arch height) or transverse plane (eg forefoot abduction) observations or measurements of foot posture or alignment (ie the construct of planal dominance).
Helbing’s sign was part of the initial version of the Foot Posture Index (FPI-8) but was removed from the more recent version (FPI-6). This was based on the inadequate concurrent validity of the sign based against an electromagnetic tracking device (Redmond et al 2006). Helbing sign was identified as problematic in the Rasch modeling of the FPI-8 (Keenan et al, 2007)
External Links:
Helbing’s sign – its lineage (Podiatry Arena)
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