The proposed study will establish novel relationships between intra-articular MSC recruitment, synovial inflammation, biomarkers of cartilage degeneration and joint inflammation, clinical patient factors, and downstream alterations in cartilage composition and morphology to provide novel insights into the pathoetiology of PTOA after ACL injury and reconstruction.

In efforts to study the pathoetiology of post-traumatic osteoarthritis (PTOA), we propose a collaborative, prospective cohort study of 38 patients undergoing primary anterior cruciate ligament (ACL) reconstruction after ACL rupture. We will assess the longitudinal progression of patient-reported outcomes, knee laxity, MRI-based articular cartilage morphology and composition, and serum-borne biomarkers of cartilage degeneration up to 1 year of follow-up. Furthermore, stem cell mobilization, chemokine and pro-inflammatory cytokine concentrations, and inflammatory cell recruitment into synovial tissue will be measured from intraoperatively-collected samples. We will perform mixed multivariate linear regression modeling to elucidate potentially novel relationships between patient demographics, anatomy, biological factors, and downstream alterations in articular cartilage morphology and composition. We request $200,000 in funding over a two-year duration.

Inclusion Criteria:

• - Males and females, aged 18 - 30 years
• Isolated, traumatic primary anterior cruciate ligament rupture requiring surgical reconstruction
• Surgical reconstruction performed using a single-bundle technique utilizing an autograft
• No history of ipsilateral traumatic knee injury or fracture
• No evidence of PCL injury or more than grade 1 injury to the MCL or LCL

Exclusion Criteria:

• - BMI < 18.5 or >35 kg/m2
• Injury occurred longer than 4 weeks before enrollment
• Intra-articular steroid injection within 3 months of injury
• Chondral defects greater than 3 cm2 or Outerbridge grade II or higher lesions

The participating physicians at each site will identify potential subjects from their clinics' patients according to the inclusion/exclusion criteria listed below. Based on surgical volumes at both sites, patients generally undergo ACL reconstruction 8-12 weeks after initial screening. In the preoperative timeframe, all patients will undergo standard physical therapy to address pain, swelling, and motion deficits, as is standard of care at both institutions.