The purpose of this study is to assess the validity and reliability of a prototype portable ankle arthrometer in various populations. There are two aims to this study. Aim 1 will look to determine the reliability and validity of a prototype portable ankle arthrometer on young adults with no history of ankle sprain, copers, and young adults with chronic ankle instability. It is hypothesized that the prototype portable ankle arthrometer will be a valid and reliable tool to assess joint laxity across the three different populations. Aim 2 will look to determine the validity of a prototype portable ankle arthrometer in young adults with an acute ankle sprain across multiple timepoints in their first month post injury. It is hypothesized that the prototype portable ankle arthrometer will be a valid tool to assess joint laxity at three different timepoints for the same individual.