A test battery for evaluation of muscle strength, balance and functional performance in subjects with chronic ankle instability: a cross-sectional study

BACKGROUND: Studies investigating ankle condition in subjects with chronic ankle instability (CAI) using an on-the-field test battery are scarce. Understanding which tests that are most challenging for these subjects has the potential to set realistic goals in rehabilitation and return-to-sports criteria. Thus, the primary aim of this study was to investigate CAI subjects regarding strength, balance and functional performance with an easily used test battery that required minimal equipment. METHODS: This study was conducted with a cross-sectional design. A total of 20 CAI subjects, engaged in sports, and 15 healthy subjects serving as a control group, were tested for assessment of strength, balance and functional performance. A test battery was developed accordingly; isometric strength in inversion and eversion, the single leg stance test (SLS), single leg hop for distance (SLHD) and side hop test. The limb symmetry index was calculated to determine whether a side-to-side lower limb difference could be classified as normal or abnormal. The sensitivity of the test battery was also calculated. RESULTS: The subjects were 20% weaker on the injured side compared with the non-injured side in eversion (p < 0.01) and 16% weaker in inversion (p < 0.01) (Table 2). For the SLS test, the mean score of the injured side was 8 points (67%) higher (more foot lifts) compared to the non-injured side (p < 0.01). The mean distance of the SLHD was 10 cm (9%) shorter for the injured side compare to the non-injured side (p = 0.03). The mean number of side hop was 11 repetitions (29%) fewer for the injured side compare to the non-injured side (p < 0.01). Six of the 20 subjects obtained abnormal LSI values in all five tests whereas none obtained normal values in all tests. The sensitivity of the test battery was 100%. CONCLUSION: Deficits in muscle strength, balance and functional performance appear to be present in CAI subjects with the largest impairments in balance and side hop performance, which stresses the need for return to sport criteria for this group of subjects. TRIAL REGISTRATION: Registered retrospectively on 24/01/2023. NCT05732168.