Recent developments on models and inclusion criteria for chronic ankle instability

Abstract

In the most recent report of injury data on 15 sports from the U.S. National Collegiate Athletic Association (NCAA) Injury Surveillance System over a span of 16 years (1988e2004), ankle ligament sprains were the most common injury. Residual symptoms such as recurrent sprains, pain, instability, and giving way are common after an initial, acute ligament sprain. Chronic ankle instability (CAI) is one of these common problems, and has enjoyed increased interest in the recent literature. However, CAI remains a poorly-defined and understood condition. CAI has been commonly associated with two types of instability, namely mechanical and functional instability. Hertel in 2002 proposed a CAI model that has been very popular (Fig. 1). In this model, CAI is attributed to both mechanical instability and functional instability. Functional instability may be caused by deficits in proprioception, neuromuscular control, postural control, and/or muscular strength. Mechanical instability may be caused by altered mechanics in one or more joints within the ankle complex. Rather than treating these two types of instability independently, this model considers that they are both part of an instability continuum. When both types of instability are present, recurrent ankle sprain occurs. In a recent paper, Hiller et al. proposed a new and updated CAI model that was evolved from Hertel’s original model. In this new model, CAI has a total of seven sub-groups (Fig. 2). In the new model, the triad consists of mechanical instability, perceived instability (instead of functional instability in