Oral Contraceptive Use Associated With Lower Rates of Knee Instability After Anterior Cruciate Ligament (ACL) Reconstruction

Background Sex hormones influence connective tissue biology and pain processing, but the relationship between oral contraceptive pill (OCP) use and postoperative outcomes after anterior cruciate ligament reconstruction (ACLR) remains unclear. The purpose of this study was to evaluate whether perioperative OCP use is associated with postoperative knee instability and other clinical outcomes after ACLR. Methods Using a multicenter database, TriNetX, females aged 14-40 years undergoing arthroscopic ACLR were grouped as OCP users (prescriptions within six months before and within two years after surgery) or non-users (no OCP prescriptions from one year before to two years after surgery). Propensity score matching (1:1) based on demographics and comorbidities yielded 815 patients per cohort. Primary outcomes were two-year reoperation, chronic knee instability diagnosis, and chronic knee pain diagnosis. Secondary outcomes included 30-day surgical site infection (SSI), 90-day deep or organ infection, six-month arthrofibrosis/manipulation under anesthesia (MUA), and postoperative opioid use (early, 1-30 days; prolonged, 30-90 days; chronic, 90-180 days). Risk ratios (RRs) with 95% confidence intervals (CIs) were calculated. Results OCP use was associated with significantly lower rates of two-year chronic knee instability (RR, 0.316; 95% CI, 0.166-0.600; p < 0.001) and early postoperative opioid use (RR, 0.363; 95% CI, 0.281-0.468; p < 0.001). Rates were similar between groups for six-month arthrofibrosis/MUA (RR, 0.750; 95% CI, 0.357-1.575; p = 0.446), two-year reoperation (RR, 1.057; 95% CI, 0.735-1.519; p = 0.766), two-year chronic knee pain (RR, 0.976; 95% CI, 0.877-1.086; p = 0.654), 30-day SSI (rare), and 90-day deep or organ infection (none; p = 1.000). Conclusion In a large propensity-matched cohort of female patients undergoing ACLR, perioperative OCP use was associated with markedly lower rates of two-year knee instability and reduced early opioid use, whereas other complications and reoperation rates did not differ, highlighting hormonal status as a potentially modifiable factor in postoperative recovery.