Inclusion Criteria:

For controls:

• The study participants must be between the ages of 12—60;
• The study participants must read and speak English.

For patients recovering from ACL injury or ACLr:

• Unilateral ACLr or unilateral ACL injury with no surgical intervention. As is common, injuries may include disruption of the meniscus, articular cartilage, or subchondral bone. Surgery may include meniscus repair or partial meniscectomy as this is a common associated finding in the setting of an ACL injury in young athletes;
• Included physical therapy interventions: Therapist will follow their own standard, typical protocol for recovery after ACL injury or ACLr;
• Between the ages of 12—60 yrs. of age;
• Testing at the time of clearance for sport or within 1 year of such clearance. There are reports that return-to-sport takes up to 2 years.

Exclusion Criteria:

For controls:

• Study participants will be excluded if any of the following are present:
  • Neurological disorders;
  • No history of lower extremity injury in the past 6 months that has prevented you from participating fully in sports activities;
  • Presence of any medical condition that would impair the participant’s ability to perform the tasks proposed in this study;
  • Study participants will be excluded if a self-reported medical condition would impair the participant’s ability to perform the tasks proposed in this study.

For patients recovering from ACL injury or ACLr:

• Excluded surgical interventions: None, consistent with inclusion criteria.
• Other:
  • Less than 2 months post-injury if no surgery was done, or less than 2 months post-surgery if surgery was done;
  • Moderate pain: Pain > 4/10 visual analog score (VSA);
  • Inability to flex affected leg between 60 and 120 degrees to achieve testing position.

Eligibility last updated 3/29/22. Questions regarding updates should be directed to the study team contact.