Objective: Adductor canal block (ACB) is commonly used for postoperative analgesia after unicompartmental knee arthroplasty (UKA). However, the comparative benefits of single-injection ACB (SACB) versus continuous ACB (CACB) remain unclear. Methods: In our retrospective cohort study, patients undergoing unilateral, primary UKA were allocated to group CACB or group SACB from January 2016 to December 2023. The primary outcome was the visual analog scale (VAS) for pain. Secondary outcomes included the additional analgesic therapy, activity score, postoperative nausea and vomiting (PONV), complications, and length of stay (LOS). Results: After 1:1 propensity score matching based on age, sex, body mass index (BMI), and preoperative pain score, 35 patients were included in each group (SACB and CACB). At 24 hours postoperatively, the SACB group had a slightly higher VAS pain score compared with the CACB group, though this difference was not statistically significant. The Post-Anesthesia Care Unit (PACU) activity score was significantly higher in the SACB group (p = 0.02), and the LOS was significantly shorter by approximately 3 days compared to the CACB group (p < 0.001). No significant differences were found between groups in terms of additional analgesic therapy, Oxford Knee Score (OKS), PONV, or complications. Discussion: CACB did not significantly reduce postoperative pain or improve functional outcomes over three months after UKA compared to SACB. However, SACB was associated with improved immediate postoperative mobility and a shorter LOS, suggesting potential benefits for early recovery.