An investigation of the relationship between a static diagnosis of ankle equinus and dynamic function of the ankle joint

Abstract

is characterised by a limited ankle joint range of motion which is usually caused by the contracture of the triceps surea muscle group. There are numerous definitions and techniques to diagnose ankle equinus. A commonly used examination utilised in a clinical setting is as described by Root et al., (1977) where passive ankle joint dorsiflexion is examined using a hand held goniometer. Several studies have proven this to be unreliable. Unfortunately literature has failed to correlate static examinations of the ankle joint with its dynamic motion. Aim: The aim of this research was to investigate whether there is a relationship between the static diagnosis of ankle equinus and the dynamic motion of the ankle joint. Research Design and Method: A quantitative non-experimental same subject research design was employed in this study. Twenty participants with a mean age of 34 years were divided into two equal groups which were of normal (0 to +5) or pronated (+6 to +10) foot type, using the foot posture index. The static examination was then carried out using a fixed goniometer, following which they were divided into two categories of ‘between -5 to 0 degrees’ or ‘less than -5 degrees’ of ankle equinus. Dynamic examination was then carried out using a 3D optoelectronic capture system where markers were placed according to the Rizzoli foot model. An average of the maximum dynamic ankle joint and foot dorsiflexion was taken. Results: No relationship was found between static examination findings and dynamic motion of ankle joint dorsiflexion. 66.7% of participants in the ‘between -5 to 0 degrees’ category had more than 10 degrees of ankle joint motion during gait. On the other hand in the 'less than -5 degrees' of static ankle equinus, all of the individuals had less than 10 degrees of dynamic ankle joint dorsiflexion but there was still an increase of average dynamic motion. Similar results were obtained in the dynamic foot dorsiflexion, where a marginal increase in dynamic ankle joint dorsiflexion was observed which was attributed to the midtarsal joint dorsiflexion. Also, a significant relationship between gender and dynamic ankle and foot motion was noted, as the female population had a higher degree of ankle joint range of motion than males. Conclusion: There was no significant correlation between the static diagnosis of ankle equinus and the dynamic motion of the ankle joint in the category of 'between -5 to 0 degrees'. This indicates that the technique as explained by Root theory is not enough to classify an individual as having ankle equinus. This implies that clinicians should carry out a dynamic examination to confirm diagnosis of ankle equinus. However, in the category of 'less than -5 degrees' of ankle equinus, the participants had less than 10 degrees of ankle joint dorsiflexion. Therefore, although there is no correlation between the two, dynamic ankle equinus was still present. This may also suggest that a standard definition of ankle equinus may be that of having less than -5 degrees of static ankle equinus.