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).
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, with anterior reach improving more modestly at 0.72. Static balance moved as well. The centre-of-pressure ellipse area shrank by 11.62 mm squared and the movement path length shortened by 56.33 mm, both statistically significant. Ankle function improved on both FAAM daily-living (mean difference 4.32) and FAAM sport (5.26). The total numbers are modest, 306 people across nine trials, so read the large effect sizes with that in mind.
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. Keep loading the ankle directly as well, because none of these trials tested hip work as a replacement for ankle rehabilitation.
Bottom line
Hip strengthening improved dynamic balance, static postural control and self-reported ankle function in chronic ankle instability, with the biggest gains in backward reach. Train the hip alongside the ankle for recurrent sprains.