Minimum Reporting Standards for Copers in Chronic Ankle Instability Research

Lateral ankle sprains (LASs) are among the most common sports-related injuries and a high percentage of individuals who sprain their ankle go on to develop chronic ankle instability (CAI). The condition of CAI is often classified as having pain, loss of function, and a restriction of, or failure to, return to levels of previous activity. Historically, uninjured healthy controls are used as a comparison group to study the biomechanical and neuromuscular consequences of CAI. However, this model is not ideal to determine why a portion of the population experiencing an ankle sprain does not recover. A more appropriate comparison may be individuals who had an ankle sprain, and thus the exposure, but did not go on to develop CAI (i.e., copers). Thus, the purpose of this review was to determine the existing discrepancies and common standards in definitions of, terminology used for, and the inclusionary/exclusionary criteria used to describe copers within the CAI literature. Multiple databases were searched by keywords and specific authors. Potential studies were screened independently by both authors. Inclusion criteria consisted of an explicit definition of copers and explicit inclusionary/exclusionary criteria. A total of 21 studies were included in the current study and had four outcomes extracted: (1) the definition of copers; (2) the terminology used; (3) specific inclusionary/exclusionary criteria; and (4) injury characteristics of the copers. Based on the included operational definitions, it is recommend that future operational definitions of copers include three key components: (1) an initial LAS; (2) subsequent lack of CAI symptoms (i.e., no complaints of disability or giving way); and (3) a time since injury component. The term coper was overwhelming used within the existing literature (n = 15) and is thus recommended to be used in future studies when describing individuals who have suffered an LAS but failed to develop CAI. Minimal inclusionary criteria should consist of three things: (1) an initial LAS severe enough to warrant either the use of a protective device (e.g., ankle brace) for at least 1 week or immobilization and/or non-weight bearing for at least 3 days, or both; (2) a return to at least moderate levels of weight-bearing physical activity for at least 12 months without recurrent injury, episodes of giving way, and/or feelings of instability; and (3) minimal, if any, level of self-reported disability. Acute head and/or lower extremity injuries that occurred ≤3 months prior to testing, a history of ankle fractures and/or surgeries, and the presence of pain (constant or intermittent) should be used as minimal exclusionary criteria in future investigations dealing with copers. Finally, at least seven items should be reported to better contextualize copers across investigations. These items should include the initial mechanism of injury, the presence of mechanical laxity, number of days immobilized and/or non-weight bearing after the initial ankle sprain, time since the latest ankle sprain, percentage of coper participants with a recurrent ankle sprain or giving way episode, current physical activity levels, and whether copers attended formal rehabilitation for their involved ankle.