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Purpose : Residual functional ankle instability regardless of the restoration of mechanical stability after the lateral ligament repair or reconstruction can cause recurrent sprain. The purpose of this study was to identify the sequential changes of joint-position sense, peroneal strength, postural control, and functional performance ability after the modified Broström procedure (MBP) for chronic ankle instability. Methods : A total of 46 patients (46 ankles) who underwent the MBP for chronic ankle instability were eligible for this study and were followed up for 1 year postoperatively. The changes of joint-position sense and peroneal strength were periodically evaluated with an isokinetic dynamometer. Postural control ability was evaluated using a one-leg stance test with eyes closed. The functional performance ability examination comprised a one-leg hop test, a six-meter hop test, and a cross three-meter hop test. Results : The error in joint-position sense significantly improved from a mean 4.3° to 2.8° ( p < 0.001). Peak torque for eversion significantly improved from a mean 18.2 Nm to 21.2 Nm ( p = 0.024). Balance retention time significantly improved from a mean 4.7 s to 6.4 s ( p < 0.001). Among the functional performance tests, only the one-leg hop test showed a significant improvement postoperatively ( p = 0.031). At 1 year postoperatively, the recovery ratios compared to the unaffected ankle were 67.9% in joint-position sense ( p < 0.001), 86.9% in peroneal strength ( p = 0.012), and 74.4% in postural control ( p < 0.001), with significant side-to-side differences. Conclusion : Although joint-position sense, peroneal strength, postural control, and functional performance ability were significantly improved after the MBP, recovery ratios compared to the unaffected ankle were insufficient up to 1 year postoperatively. Level of Evidence : Level IV (prospective case series).