The other subjects who did not fit into the model had recurrent ankle sprains, but did not present with mechanical or functional instability. Among the 108 ankles used to fit the updated model, the percentage of the classifications see more was 42.6% (46) for perceived instability, 30.5% (33) for perceived instability plus recurrent sprain, 11.1% (12) for perceived instability plus mechanical instability and recurrent sprain,
9.3% (10) for mechanical plus perceived instability, 2.8% (3) for recurrent sprain, 2.8% (3) for mechanical instability, and 0.9% (1) for mechanical instability plus recurrent sprain.3 In addition to the expanded sub-groups, functional instability is referred to as perceived instability in the newer model “because functional instability is now used with widely different meanings”.3 Several limitations were acknowledged by the authors. The model was tested retrospectively using data from previous studies. Only one method was used to test mechanical instability, perceived instability and recurrent sprain in the original data sets. Mechanical instability was examined using an anteroposterior manual testing method. The model was tested with data
from limited age and activity groups. Finally, the sample size for some sub-groups was rather small. Although research interest in CAI has increased steadily in recent years, the results are rather inconsistent.2 This may be largely related to the different
criteria used to define functional instability, which Selleckchem Capmatinib may have led to subject groups with different instability characteristics. In a recent extensive literature review of 118 studies on the inclusion criteria of CAI studies, Delahunt et al.2 showed that the most common descriptors for ankle instability and functional instability are frequent ankle sprains and ankle joint giving way. However, most of the studies using the concept most of giving way did not actually define or describe the concept. It is also unclear if giving way is the same as a feeling of ankle instability. Therefore, in order to avoid confusion, these authors provided operational definitions for mechanical instability, functional instability, CAI, recurrent ankle sprain, “giving way” of the ankle, the feeling of ankle instability, and acute lateral ankle sprain.2 These clearly defined terms may help minimize discrepancies in the targeted populations, and select more homogenous subject cohorts in future CAI studies. In addition to having clearly defined operational terms, the usage of ankle instability surveys such as the Foot and Ankle Ability Measure,7 Ankle Joint Functional Assessment Tool,8 and Cumberland Ankle Instability Tool9 can quantify functional instability and further differentiate CAI patients from healthy controls. For mechanical instability, its presence should be assessed through instrumented measures or manual testing.