Ankle strength is not strongly associated with postural stability in patients awaiting surgery for chronic lateral ankle instability



(1) To describe ankle strength and postural stability in patients with chronic lateral ankle instability and (2) to analyse the correlation between deficits in ankle strength and postural stability.


Results of preoperative isokinetic and balance tests in 203 patients whose contralateral ankle was normal were retrospectively reviewed. Isokinetic peak torque values of eversion and inversion at 2 angular velocities (30°/s and 120°/s) were measured in the injured and normal ankles. In the balance test, the percent differences of 3 actual scores (overall, anterior–posterior, and medial–lateral) between the injured and normal ankles were calculated. Additional statistical analyses were performed to evaluate weakness of ankle strength, postural stability deficits, and their correlation.


Significant differences in 4 peak torque values and 4 relative peak torque values (peak torque/body weight) were found between the injured and normal ankles. All 8 values were significantly lower in the injured ankles. Weakness was severe during inversion and at 30°/s. In the balance test, 49 subjects (24.1%) had significant deficits in postural stability and 109 (53.7%) had favourable results. No strong association was found between weakness of ankle strength and deficits in postural stability.


Strength measurement alone is insufficient to evaluate preoperative functional deficits, and other functional tests are required to measure postural stability. The results of this study provide further evidence for a rehabilitation programme consisting of proprioceptive training as well as strengthening. The proprioceptive training must be an integral part of the rehabilitation programme in addition to strengthening exercise.

Level of evidence

Case series, Level IV.

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Correspondence to Ki-Sun Sung.

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See Tables 7 and 8.

Table 7 Reported intraclass correlation coefficient of the stability index of the Biodex Stability System
Table 8 Test–retest reliability of the measurement systems in the pilot study

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Ko, K.R., Lee, H., Lee, W. et al. Ankle strength is not strongly associated with postural stability in patients awaiting surgery for chronic lateral ankle instability. Knee Surg Sports Traumatol Arthrosc 28, 326–333 (2020).

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  • Chronic ankle instability
  • Ankle strength
  • Postural stability
  • Rehabilitation