Preoperative Loss of Knee Extension Affects Knee Extension Deficit in Patients After Anterior Cruciate Ligament Reconstruction

BACKGROUND: Loss of knee extension (LOE) after anterior cruciate ligament reconstruction (ACLR) is associated with limited knee joint function and increased risk for knee osteoarthritis. HYPOTHESIS: Preoperative LOE will affect postoperative LOE for up to 12 months after ACLR. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Included were patients who underwent anatomic ACLR between June 2014 and December 2018. In all patients, the postoperative rehabilitation protocol was the same. A heel height difference (HHD) ≥2 cm between the affected and the contralateral leg was used as a measure of LOE. Based on preoperative HHD, patients were divided into LOE and no-LOE groups. The HHD was reevaluated at 1, 3, 4, 6, 9, and 12 months postoperatively. Proportional hazards analysis was used, with the dependent variable being whether a postoperative HHD <2 cm was achieved; the independent variables being the presence or absence of preoperative LOE; and the adjusted variables being age, sex, time to surgery, and presence of meniscal sutures. RESULTS: A total of 389 patients (208 female, 181 male; median age, 21.0 years) were included in the study. There were 55 patients in the LOE group and 334 patients in the no-LOE group. The incidence of LOE at 12 months after ACLR was 13.8% in the no-LOE group and 38.2% in the LOE group (P < .001), with an absolute risk difference of 24.4%. The hazard ratio for achieving postoperative HHD <2 cm was 2.79 for the LOE group versus the no-LOE group (P < .001). CONCLUSION: Patients with preoperative LOE were nearly 3 times more likely than those without LOE to have LOE at 12 months after ACLR.