Research Study Participation

• completed a prescreening questionnaire that determined you are eligible for this study
• are currently between the ages of 18 and 30 and
• are physically active as defined by reporting a 5 or higher current activity level on the Tegner Activity Scale with no prior history of major injury requiring medical care or surgery to your lower body

• Younger adults aged 18–35 years with a body mass index (BMI) of 18.5–34.9 kg/m².
• Older adults aged 65 years and older with a body mass index (BMI) of 18.5–34.9 kg/m².

• are between the ages of 18-35 years,
• either have had an anterior cruciate ligament reconstruction (ACLR) surgery or have not had an injury to either of your knees,
• have not been medically diagnosed with a concussion in the previous 6 months,
• have not been medically diagnosed with colorblindness,
• have no known neurological (nervous system) disorder (i.e. Multiple Sclerosis),
• have not taken opioid medication (pain medication) in the last 2 weeks,
• are not pregnant of planning to become present during study participation, and
• have no contraindications to brain MRI (you will complete a screening form).

ACL Group:

• Age of 18-35 years
• History of only one ACL reconstruction within the previous 2 years
• Medical clearance for return to unrestricted activity

Uninjured Group:

• Age of 18-35 years
• No history of lower limb surgery
• No history of significant lower limb injury within previous 6 months (defined as seeking medical attention, or missing >3 consecutive practices or games)

• Age 12-45 years
• History of knee injury (e.g., ACL tear, meniscus tear, patellofemoral pain, osteoarthritis) or surgery (e.g., ACL reconstruction, meniscectomy or repair, total knee arthroplasty) within the last 2 years