The association between activity level after anterior cruciate ligament (ACL) reconstruction (ACLR) and development of posttraumatic osteoarthritis (PTOA) remains unclear. This study investigated the relationship of patient-reported outcomes and progressive cartilage degenerative changes at 3 years after ACLR.
Higher activity levels, as measured by Marx scores, are significantly correlated with early cartilage degeneration after ACLR.
Cohort study; Level of evidence, 2.
A total of 35 patients (16 women; mean age, 31.0 ± 7.6 years) with isolated ACLR and without pre-existing arthritis were prospectively enrolled. Patients reported Marx activity scores and Knee injury and Osteoarthritis Outcome Score (KOOS) scores and underwent T
Sixteen patients (45.7%) showed evidence of cartilage degeneration at 3 years, most frequently in the medial compartment (n = 12; 34%). Higher Marx activity scores at 3 years correlated with cartilage degeneration in the medial femur (rho = 0.34; 
Increased activity at 3 years after ACLR was significantly associated with increased risk of medial compartment PTOA. While further research is needed to fully define these relationships, patients may be counseled that return to Marx activity levels of greater than 11 may be associated with a higher risk of medial compartment cartilage degeneration.