The study
A systematic review and meta-analysis gathered nine randomised trials, 306 people with chronic ankle instability, the recurrent giving-way and re-spraining that can follow a bad ankle sprain. It compared hip strengthening against control. The outcomes were dynamic balance on the Star Excursion or Y-Balance Test (reaching as far as possible on one leg in set directions), static balance from centre-of-pressure measures, and the Foot and Ankle Ability Measure (FAAM, a validated self-report of ankle function). Interventions ran 4 to 12 weeks, and overall study quality was moderate to high.
What they found
Dynamic balance improved clearly, and most of all in the backward directions: posterolateral reach came out at a standardised mean difference of 1.35 and posteromedial at 1.66, both large effects. Ankle function improved too, on both FAAM daily-living (mean difference 4.32) and FAAM sport (5.46). Static balance was the weaker spot. One centre-of-pressure measure improved, but sway path length and velocity did not reach significance. The total numbers are modest, 306 people across nine trials.
What it means for your practice
For the recurrent-sprain patient, this is a reason to train the hip, not only the ankle. Hip strengthening improved how far and how steadily these patients could control a single-leg reach, especially reaching backward, and that carried through to how they rated their own ankle function.
It fits the chain picture. The ankle is where the instability shows, but a good part of the control that protects it runs up through the hip. Add hip strength, the abductors, extensors and external rotators, and single-leg control work to the usual peroneal strengthening and balance training. Do not expect it to clean up every static-balance measure, and keep loading the ankle directly as well.
Bottom line
Hip strengthening improved dynamic balance and ankle function in chronic ankle instability, with static balance less consistent. Train the hip alongside the ankle for recurrent sprains.