Subjects (both cases and controls) were recruited as part of a large prospective observational study and completed balance testing from August 2017 through July 2018. Controls were recruited from a private suburban high school. At the time of testing, controls were beginning participation in their respective soccer, basketball, and lacrosse seasons. Cases were recruited as a convenience sample from the same private suburban high school, as well as from the concussion program of a tertiary care academic pediatric center, a referral program that evaluates patients with acute injury. Cases received a diagnosis of concussion in accordance with the 5th Consensus Statement on Concussion in Sport (19 (link)); none of the assessments utilized in this study were used to diagnose a subject with a concussion. All cases presented with a sport- or recreation-related injury, with assessments completed within 28 days of injury. Exclusion criteria for both cases and controls included an injury of the lower extremities (defined as an injury with use of an active support device, such as a brace, walking boot, splint, cast, or crutches; or an injury visibly affecting gait), being within one month of clearance from a previous concussion. Any subject who sustained a concussion during the study period was included in the case cohort only. Informed consent from a parent or guardian and child assent was obtained for those under 18 years of age prior to enrollment, and informed consent from the study subject was obtained directly for those 18 years of age or older. The study was approved by the Institutional Review Board of the Children’s Hospital of Philadelphia.