Predictors of a Symptomatic Knee Following ACL Reconstruction: 84 Month Follow Up

OBJECTIVES: ACL reconstruction is effective in restoring knee stability and returning a majority of patients to sports. However, these patients remain at a higher risk of developing knee OA and a subset of patients have persistent pain. It is currently unknown what pre-operative and early post-operative measures can be used to help predict outcomes following ACL reconstruction at 7 years. The purpose of this study was to compare clinical data, patient-reported outcomes and imaging findings of knee arthrosis between symptomatic and asymptomatic subject at 84 month follow up after primary ACL reconstruction. METHODS: We reviewed prospectively collected data from our previously published randomized controlled trial of outcomes of ACL reconstruction. Clinical, radiographic, and patient-reported outcomes were collected pre-operatively, and at 1,3,5, and 7 years post-operatively. Patient-reported outcome measures included SF-36 and KOOS. Imaging studies were used to evaluate medial joint space width, Osteoarthritis Research Society International (OARSI) radiographic score, and Whole-Organ Magnetic Resonance Imaging Score (WORMS). Symptomatic subjects were defined as those with KOOS-pain subscores, measured at 84 months post-operatively, two standard deviations below the mean for healthy athletic patients with a history of a knee ligament injury. These subjects were compared to the remainder of the study group to identify factors predictive of poor outcomes. RESULTS: patient-report outcome measures were available for 72 patients at 84 month follow up. Of these, 7 subjects had KOOS pain scores less than 72.5 and were considered the symptomatic subgroup. Low pre-operative KOOS-ADL and KOOS-sports subscores were associated with low KOOS pain scores at 7 year follow up. SF-36 scores were lower at most time periods in the symptomatic group. In addition, OARSI scores were worse at 1,5, and 7 years, and WORMS showed greater signs of cartilage injury at 3 and 5 years post operatively in the symptomatic group. Medial joint space width was found to be significantly decreased in symptomatic patients at 7 year follow up. CONCLUSION: Low preoperative KOOS-ADL and KOOS-sports subscores were found to be associated with worse pain outcomes in primary ACL reconstruction patients at 84 months post-operatively. Additionally, multiple post-operative measures were found to be indicative of the ACL reconstruction patients that would have a symptomatic knee. WORMS collected at 3 and 5 years was shown to identify those subjects that would be symptomatic at 7 years. Also, radiographic changes were evident in this group with significantly decreased medial joint space width relative to control subjects.