Abstract
BACKGROUND: Limb symmetry index (LSI) of the anterior reach Y-Balance test (YBT) after anterior cruciate ligament (ACL) reconstruction is related to the knee extensor strength LSI. However, a specific cutoff point predicting knee extensor strength LSI at six months postoperatively does not exist. # Purpose To determine a cutoff point for the anterior reach distance LSI at three months postoperatively to identify patients who will not achieve the knee extensor strength LSI ≥90% at six months postoperatively. # Study Design Retrospective cohort study. # Methods Patients who underwent primary ACL reconstruction using hamstring tendon autograft were included for this study. Patients with injured contralateral ACL, knee ligaments other than the ACL or cartilage damage were excluded. Post-ACL reconstruction, athletes were measured for YBT anterior reach distance at three months and isokinetic knee extensor strength at six months; their respective LSIs were calculated. Cutoff points for anterior reach distance LSI at three months postoperatively to identify if knee extensor strength would be achieved at six months postoperatively were determined using a minimum p-value approach, and phi coefficients; sensitivity and specificity were also calculated. # Results Data from 90 patients (53% female, age: 21(12.5) years) who met the inclusion criteria were analyzed. The cutoff point of 90% for the anterior reach distance LSI yielded the lowest p-value and highest chi-square value (p=0.010, chi-square value=6.553). At the cutoff point, a significant association was found between the anterior reach distance LSI at three months and the knee extension strength LSI at six months (φ=0.270), with a sensitivity of 38.1% and a specificity of 88.9%. # Conclusions Patients with an anterior reach distance LSI of <90% at three months postoperatively are at higher risk of not achieving a knee extension muscle LSI of 90% at six months. Anterior reach distance LSI can be safely measured daily during the early postoperative phase; therefore, it may help guide postoperative planning for rehabilitation until return-to-sport discussions begin. LEVEL OF EVIDENCE: 3.