Validation of Foot and Ankle Ability Measure (FAAM) and the Foot and Ankle Outcome Score (FAOS) in individuals with chronic ankle instability: a cross-sectional observational study

BACKGROUND: Ankle sprain is the most common lower limb injury in physically active individuals. Loss of function, decreased postural control (PC), strength deficit, and reduced range of motion (ROM) are common after acute lateral ankle sprains. Some patients experienced long lasting symptoms, with recurrent sprains, and episodes of giving-way: a condition known as chronic ankle instability (CAI). Evaluating the function in patients with CAI in the clinical environment is important to identify the severity of the condition, in addition to allowing to assess the effectiveness of a given treatment. The aim of this study was to investigate the validation of the Foot and Ankle Ability Measure (FAAM) and the Foot and Ankle Outcome Score (FAOS) in terms of muscle strength, PC and ROM in adults with CAI. METHODS: This is a cross-sectional study. Individuals with CAI aged between 18 and 45 years were eligible. Individuals with CAI were identified using the Identification of Functional Ankle Instability (IdFAI). All patients filled in the FAAM and FAOS scores. Muscle strength was assessed by manual dynamometry, ROM by the Lunge test, PC by computerized posturography, modified Star Excursion Balance Test (mSEBT) and modified Balance Error Score System (mBESS). RESULTS: 50 participants were enrolled in the present study. The mean age of the patients was 27.2 ± 6.3 years, and the mean body mass index was 26.4 ± 4.8 kg/m(2). 58% (29 of 50) were men and 42% (21 of 50) women. 18 individuals had unilateral (36%) and 32 bilateral (64%) CAI. The results of FAAM were associated with MCT, mSEBT, invertor muscles strength, plantar flexor muscles strength, dorsiflexor muscles strength, and external hip rotator muscles strength (P < 0.05). The results of FAOS were associated with mSEBT, invertor muscles strength, plantar flexor muscles strength, dorsiflexor muscles strength, evertor muscles strength, and external hip rotator muscles strength, and mBEES (P < 0.05). CONCLUSION: Both the FAAM and FAOS demonstrated validity to evaluate postural control and muscle strength in patients with CAI, while no association was found in relation to ankle dorsiflexion. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13018-022-02925-9.