Proceedings of The Physiological Society
University College London December 2005 (2006) Proc Physiol Soc 1, PC21
Altered ankle joint kinematics during dynamic activity in subjects with functional ankle instability (FAI)
Delahunt, Eamonn; Monaghan, Kenneth; Caulfield, Brian;
1. School of Physiotherapy and Performance Science, University College Dublin, Dublin, Ireland.
FAI is a term used to describe patients who sustain multiple ankle inversion injuries with slight or no external provocation (Konradsen & Magnusson, 2000). It is a common cause of residual disability following ankle sprains, affecting up to 60% of individuals who suffer an initial ankle sprain (Kannus & Renstrom, 1991). Previous research has suggested that FAI may be associated with altered feed-forward motor control. The purpose of this study was to investigate dynamic movement control during functional activities in FAI subjects compared with controls. We compared kinematic profiles of FAI (n=24) and control (n=22) subjects during 3 dynamic functional activities; treadmill walking at 4 km h-1, 1 m jump for distance, and 30 cm lateral hop. FAI subjects met the inclusion criteria described by Caulfield & Garrett (2004), whilst control subjects had no history of ankle sprain. Kinematic data were recorded using a CODA MPX30 3D motion capture system (Charnwood Dynamics Ltd, UK) at a sampling rate of 200 Hz. Average values from 10 trials of each activity for hip, knee and ankle joint 3D angular displacements were calculated for each subject and group mean time averaged profiles were calculated for the period from 200 ms prior to and following initial contact (IC). Differences in FAI and control group time averaged profiles were tested for statistical significance using independent two-sided t tests. (1) Walking (24 FAI and 22 control subjects): FAI subjects exhibited a decrease in toe clearance during the time period 150 ms to 100 ms pre IC (P<0.05). They also exhibited a more inverted position of the ankle joint during the time period 95 ms pre IC to 50 ms post IC (P<0.05). (2) 1 metre jump for distance (11 FAI and 13 control subjects): FAI subjects exhibited a significant increase in ankle joint inversion during the period 70 ms pre initial contact (IC) to 30 ms post IC (P<0.05). (3) Hopping (13 FAI and 16 control subjects): FAI subjects exhibited a significant increase in ankle joint inversion during the time period 10 ms pre IC to 200 ms post IC (P<0.05). A more inverted position of the ankle joint upon IC will cause the subtalar joint axis to remain in a more lateral position. Consequently a greater external inversion load may be exerted on the ankle joint, increasing the potential for a repeated inversion injury. The timing of the observed changes suggests an alteration in feed-forward control. The fact that FAI subjects have shown a consistent change in movement control in 3 separate functional activities suggests a possible position error in motor programming.
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