Validation of a Chinese translation of the identification of functional ankle instability questionnaire

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Validation of a Chinese translation of the identification of functional ankle instability questionnaire

Ankle sprains are one of the most common sports injuries—accounting for about 40% of all cases—and a troubling 20% to 33% of people who sprain an ankle go on to develop functional ankle instability (FAI). FAI is a condition where the ankle feels weak, unsteady, or “gives way” during daily activities or sports, but it lacks a universal, measurable definition. For years, doctors have treated FAI alongside ligament injuries (like anterior talofibular or calcaneofibular ligament damage), but unclear diagnoses have led to unnecessary surgeries in China—where imaging alone sometimes drives decisions, even when FAI isn’t certain. That’s why a team of Chinese researchers set out to fill a critical gap: creating a validated Chinese version of the Identification of Functional Ankle Instability (IdFAI) questionnaire, the most accurate tool recommended by the International Ankle Consortium.

The IdFAI is one of three questionnaires the Consortium endorses for FAI assessment, and it outperforms others in accuracy. Until now, no Chinese translation existed—even though China has the world’s largest population of FAI patients. To develop the Chinese IdFAI (IdFAI-C), the team followed strict cross-cultural adaptation guidelines:

  1. Forward translation: Two bilingual experts—a foot and ankle surgeon and an English teacher (both native Chinese speakers)—translated the original IdFAI into Chinese independently.
  2. Back-translation: Two native English speakers translated the initial Chinese version back into English to confirm alignment with the original.
  3. Refinement: A team of two more foot and ankle surgeons, two experienced English teachers, and the original translators polished the draft.
  4. Pilot testing: 20 Chinese college students completed the preliminary IdFAI-C and were interviewed to ensure every question was clear.

To validate the final IdFAI-C, the researchers recruited 358 college students from 51 schools and 21 cities across China in March 2019. They excluded anyone with a history of lower-limb surgery, fractures, or severe leg injuries in the past three months (that required more than one day of rest). After removing 74 ineligible participants and 16 questionnaires with inconsistent answers, 268 students (average age 25, 142 women) remained. Of these, 126 exercised more than three times a week (90+ minutes total), and 176 had a history of ankle sprains. One month later, 100 students retook the IdFAI-C to test reliability.

The team used the minimal acceptable criteria for FAI—widely accepted by experts—to measure validity: a history of ankle sprain plus self-reported “giving way” in the same ankle. They calculated the Youden index (a metric for balancing sensitivity and specificity) to find the best cutoff score for FAI: 7. That means students who scored 8 or higher likely had FAI, while scores 7 or lower meant no FAI.

The results were strong:

  • Discriminative validity: The IdFAI-C’s ability to distinguish between FAI and non-FAI (measured by the area under the receiver operating characteristic curve, or AUC) was 0.89 (on a 0–1 scale, 0.89 is “excellent”).
  • Accuracy: At the cutoff of 7, the IdFAI-C was 94% sensitive (caught almost all true FAI cases) and 73% specific (few false positives), with an overall accuracy of 79%.
  • Consistency: Cronbach’s alpha (a measure of how well questions work together) was 0.80—indicating high internal consistency.
  • Reliability: The intra-class correlation coefficient (ICC, which measures how similar results are when the questionnaire is taken twice) was 0.98—almost perfect test-retest reliability.

Compared to the original English IdFAI, the IdFAI-C has higher sensitivity (catches more FAI cases) but lower specificity (more false positives). Two factors explain this:

  1. Cultural differences: Many Chinese people don’t see a doctor for minor sports injuries—they rest at home or use traditional medicine. When asked if they’d seen a healthcare provider (question 3), most said “no,” lowering total scores. Nearly half of participants with a sprain history (84/176) hadn’t seen a professional.
  2. Translation challenges: The idiom “giving way” (a key FAI symptom) is hard to translate directly into Chinese. The team used “Shi Kong Gan” (“a feeling of emptiness or loss of control”) but added an explanation because some students didn’t grasp the nuance initially.

The study has limitations: it only included college students, so results may not apply to older adults or people with different occupations. Volunteers might also have different traits than non-volunteers, introducing bias.

Despite these limits, the IdFAI-C is a valid, reliable tool for Chinese clinicians. It shifts FAI diagnosis from imaging alone to patient-reported symptoms—helping avoid unnecessary surgeries and improving care. For a country where clear FAI diagnoses are critical, this is a major step forward.

This study was published in the Chinese Medical Journal in 2020 by Hao Guo, Wei-Qi Huang, Xi-Jiang Lin, Bo-Tao Chen, and Can-Jun Zeng from the Department of Foot and Ankle Surgery at The Third Affiliated Hospital of Southern Medical University in Guangzhou, China.

doi:10.1097/CM9.0000000000001020

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