Objective
The purpose of this investigation was to document the isokinetic performance deficiencies of the invertor and evertor muscles of chronically sprained ankles.

Method
Eversion/Inversion testing was performed by a Cybex 6000 isokinetic dynamometer at the speeds of 60^o/sec and 120^o/sec on 17 subjects who had unilateral chronic ankle sprain. Values were compared between the involved and uninvolved sides.

Results
The inversion peak torque deficits between the involved and uninvolved extremities were significantly greater than eversion deficits at 60^o/sec and 120^o/sec. Evertor/Invertor peak torque ratios of involved sides at 60^o/sec were significantly greater than uninvolved sides.

Conclusion
We conclude that chronic ankle sprains associate an ankle invertor weakness rather than an evertor weakness. Ankle invertor weakness might be resulted from a disuse atrophy and painful ankle inversion. Further prospective study is needed to determine the relationship between the invertor weakness and the chronic ankle sprain.