Background Chronic ankle instability (CAI) is characterised by repeated ankle sprains with subsequent symptoms of pain, weakness and giving way. It is important to appropriately identify individuals in the high school setting that suffer from CAI and could benefit from rehabilitation.

Objective The purpose of this study was to determine specific cutoff scores that identify high-school patients with CAI.

Design Case-control study.

Setting High school.

Patients (or participants) A total of twenty-six participants were used for the study. CAI group: (n = 13, height = 172.23 ± 8.34 cm, body mass = 79.69 ± 22.63 kg, age = 16.69 ± 1.03 years). Healthy group: (n = 13, height = 174.00 ± 6.88 cm, body mass = 62.78 ± 5.15 kg, age = 16.31 ± 1.18 years).

Interventions Four balance tests were used. Static measures included the time in balance test and the foot-lift test, and dynamic measures included the Star Excursion Balance Test (antero-medial, medial and postero-medial reach directions) and the side-hop test.

Main outcome measurements Balance was measured utilising the following: time in balance measured length of time balancing (sec), foot-lift measured number (score) of foot lifts, SEBT measured distance reached (cm) and side-hop measured time to complete (sec). We calculated area-under-the-curve values and cutoff scores and used a 1-tailed fisher exact test to determine if participants with and without CAI could be characterised using the cut-off scores.

Results We found significant area under the curve values for time in balance, foot lift, Star Excursion Balance Test (antero-medial) and side hop. Significant cutoff scores were noted for time in balance (≤ 23.5 sec), foot-lift (≥4 lifts), SEBT: antero-medial direction (≤ 0.87), medial direction (≤ 0.86) and side-hop (≥ 9.81 sec).

Conclusions These cutoff scores can assist clinicians in identifying individuals that suffer from CAI and could benefit from rehabilitation to decrease their symptoms and improve balance.