Optimizing Gait Biomechanics for Posttraumatic Osteoarthritis Prevention

• Real-time gait biofeedback (Behavioral): The RTGBF interventions will include eighteen step gait training sessions. The intervention will gradually increase to 3,000 steps at the 9th and 10th session with 100% feedback. During the remaining sessions, the intervention will include 3,000 steps, but the feedback will be gradually tapered off starting with the 11th session.
• Sham real-time gait biofeedback (Behavioral): The Sham RTGBF interventions will include eighteen step gait training sessions. The intervention will gradually increase to 3,000 steps at the 9th and 10th session with 100% feedback. During the remaining sessions, the intervention will include 3,000 steps, but the feedback will be gradually tapered off starting with the 11th session.

Primary outcomes

• Number of participants recruited using different recruitment modes [Baseline (pre-intervention)]: The investigators will record the number of participants who were recruited, the frequency at which they were recruited, and where they were recruited from. Range 0-70. Higher number indicates more completion.
• The frequency of participant recruitment using different recruitment modes [Baseline (pre-intervention)]: The investigators will record the number of participants who were recruited, the frequency at which they were recruited, and where they were recruited from. Range 0-70. Higher number indicates more completion.
• Percentage of participants who were successfully enrolled [Baseline (pre-intervention)]: The investigators will record the number of participants who were successfully enrolled compared to the total number of participants screened. Range: 0-100. Higher percentage indicates more enrollment.
• Percentage of participants retained [After week 4 and after week 8]: Investigators will record the percentage of patients retained at each monthly data capture timepoint.
• Reasons for refusal to enroll [Baseline (pre-intervention)]: Investigators will record the reasons participants opt not to enroll in the study to determine whether there is a trend.
• Number of subjects who adhered to the intervention [About 2 months]: Percent of subjects who completed the sequence of training sessions and retention sessions. Range: 0-100. Higher percentage indicates more completion

Secondary outcomes

• The change in vertical ground reaction force before and after intervention [Up to 2 months]: Participants walked on a dual-belt force-sensing treadmill for 3000 steps while vertical ground reaction forces were collected. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest. An increase in vertical ground reaction force at weeks 6 and 8 from baseline indicates improved gait mechanics
• The change in T1ρ MRI relaxation times before and after intervention [Up to 2 months]: MRI imaging provided cartilage compositions that were used to measure T1ρ relaxation times. The T1ρ MRI relaxation times refer to the proteoglycan density within the tibial and femoral cartilage. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest. Lower T1rho relaxation times reflects a better outcome.
• The change in T1ρ MRI relaxation times in the medial femoral condyle before and after intervention [Up to 2 months]: MRI marker of T1rho relaxation times of medial femoral articular cartilage (i.e proteoglycan density). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in T1ρ MRI relaxation times in the lateral femoral condyle before and after intervention [Up to 2 months]: MRI marker of T1rho relaxation times of lateral femoral articular cartilage (i.e proteoglycan density). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in T1ρ MRI relaxation times in the medial tibial condyle before and after intervention [Up to 2 months]: MRI marker of T1rho relaxation times of medial tibial articular cartilage (i.e proteoglycan density). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in T1ρ MRI relaxation times in the lateral tibial condyle before and after intervention [Up to 2 months]: MRI marker of T1rho relaxation times of lateral tibial articular cartilage (i.e proteoglycan density). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in the Knee Injury and Osteoarthritis Outcome Quality of Life subscale score [Up to 2 months]: Knee injury Osteoarthritis Outcome Score (KOOS) Quality of Life subscale to measure knee-related quality of life at pre-intervention (baseline). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest. A higher score indicates better knee-related quality of life. Range: 0-100.
• The change in the International Knee Documentation Committee Subjective Knee Evaluation form score [Up to 2 months]: The International Knee Documentation Committee (IKDC) Subjective Knee Evaluation form is a 10-item survey that determines patient-reported knee-related function. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest. A higher score indicates better knee function. Range: 0-100.
• The change in the Tegner Activity Scale score [Up to 2 months]: The Tegner Activity Scale (TAS) to quantify activity levels in individuals with ACL injury on an 11-point Likert scale. A higher score indicates a higher level of activity (e.g., a 10 indicates participants compete in professional or collegiate levels of sport on a regular basis while a 0 indicates indicates that participants are unable to complete any sport or recreational activity due to disability). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in the Anterior Cruciate Ligament Return to Sport After Injury Scale score [Up to 2 months]: The Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) scale to measure an individual's psychological readiness to return to sport. Range: 0-100 points. A lower score on this questionnaire indicates poorer psychological readiness. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in the Visual, Aural, Reading/Writing, and Kinesthetic Questionnaire score [Up to 2 months]: The Visual, Aural, Reading/Writing, and Kinesthetic (VARK) Questionnaire to quantify a participant's preferred learning styles from four learning styles (Visual, Aural, Reading/Writing, and Kinesthetic). Range: 0-16 for each learning style. Higher scores in one learning style indicates the participant's preferred learning style. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in peak vGRF [Up to 2 months]: Gait biomechanics collected using an eight camera three-dimensional motion analysis system while participants walk on a dual-belt, force-sensing treadmill will be used to quantify peak vGRF. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in peak knee flexion excursion [Up to 2 months]: Gait biomechanics collected using an eight camera three-dimensional motion analysis system while participants walk on a dual-belt, force-sensing treadmill will be used to quantify peak knee flexion excursion. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in peak internal knee extension moment [Up to 2 months]: Gait biomechanics collected using an eight camera three-dimensional motion analysis system while participants walk on a dual-belt, force-sensing treadmill will be used to quantify peak internal knee extension moment. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in joint tissues metabolism by assessing biomarker chemokine (monocyte chemoattractant protein-1 (MCP-1)). [Up to 2 months]: Blood for serum-based biomarker chemokine (monocyte chemoattractant protein-1 (MCP-1)). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in joint tissues metabolism by assessing degenerative matrix metalloproteinase-3 (MMP-3) enzyme. [Up to 2 months]: Blood for serum-based biomarker degenerative matrix metalloproteinase-3 (MMP-3) enzyme. This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.
• The change in joint tissues metabolism by assessing marker of cartilage turnover (cartilage oligomeric matrix protein (COMP)). [Up to 2 months]: Blood for serum-based biomarker marker of cartilage turnover (cartilage oligomeric matrix protein (COMP)). This will be collected at Baseline (pre-intervention), Week 6 posttest, and Week 8 posttest.

Sex: All, ages: 18 Years to 35 Years

Inclusion Criteria:

* Have completed all other formal physical therapy
* Are between the ages of 18 and 35
* Underwent an ACLR between 6 and 24 months prior to enrollment.
* Demonstrate underloading during gait (vGRF- impact peak <1.09 x BW)
* Demonstrate clinically relevant-knee symptoms (KOOS-QOL <72)
* Have undergone ACLR surgery

Exclusion Criteria:

* ACLR revision surgery
* A multiple ligament surgery
* A lower extremity fracture
* Knee osteoarthritis
* The participant has a BMI ≥ 36.

• Brian Pietrosimone, Principal investigator, University of North Carolina, Chapel Hill