Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction

Objective: To identify preoperative predictive factors for knee function two years after reconstructive surgery of the anterior cruciate ligament (ACL). The main hypothesis was that preoperative quadriceps strength would be the most significant predictor for knee function two years after reconstructive surgery. Design: Cohort study. Setting: ACL injured individuals treated at a University Hospital and an outpatient clinic in Oslo, Norway. Participants: Seventy-three individuals with complete unilateral rupture of the ACL scheduled for reconstruction with a bone-patellar-bone autograft were included in the study, from where 60 were available for two-year follow up and included in the final analyses. Interventions: Not applicable. Main outcome measurements: Identification of baseline independent variables that may predict knee function assessed with the Cincinnati Knee Score as dependent variable two years after ACL reconstruction. Results: Quadriceps muscle strength, meniscus injury and the Short-Form-36 Bodily Pain sub score were identified as significant predictors for knee function assessed from the Cincinnati Knee Score two years after ACL reconstruction. Individuals with preoperative quadriceps strength deficits above 20% also had persistent significantly larger strength deficits two years after surgery. Conclusions: Preoperative quadriceps muscle strength deficits and meniscus injuries have significant negative consequences for the long-term functional outcome after ACL reconstruction. From our findings we suggest that ACL reconstruction should not be performed before quadriceps muscle strength deficits of the injured limb is less than 20% of the uninjured limb.