Objective:To evaluate the effect of ultrasound-guided adductor canal block with bupivacaine liposome on analgesia in elderly patients undergoing total knee arthroplasty.Methods:This was a prospective study. Sixty American Society of Anesthesiologists Physical Status classification Ⅱ or Ⅲ patients, regardless of gender, aged 65-83 yr, weighing 50-80 kg, scheduled for elective unilateral total knee arthroplasty under subarachnoid anesthesia from April 2023 to January 2024 in Zhengzhou Orthopaedic Hospital, were divided into 2 groups ( n=30 each) using a random number table method: bupivacaine liposome group (LB group) and ropivacaine group (R group). Ultrasound-guided adductor canal block was performed at 30 min before subarachnoid anesthesia, bupivacaine liposome diluent 20 ml (133 mg) was injected in LB group, and 0.5% ropivacaine 20 ml was injected in R group. Patient-controlled intravenous analgesia was performed after operation, and tramadol was used for rescue analgesia when the visual analogue scale (VAS) score ≥3. VAS scores at rest and during activity were recorded at 8, 12, 24, 48 and 72 h after surgery. The time to the first pressing analgesia pump and rescue analgesia were recorded within 72 h after surgery. The quadriceps muscle strength was measured at 1 day before surgery and 12, 24, 48 and 72 h after surgery. The knee joint range of motion was assessed at 1 day before surgery and 24, 48 and 72 h after surgery. Patient′s satisfaction with analgesia was recorded at 72 h after surgery. The adverse reactions within 72 h after surgery were also recorded. Results:Compared with R group, VAS scores at rest and during activity were significantly decreased at 12, 24, 48 and 72 h after surgery, the time to the first pressing analgesia pump was prolonged, the rate of rescue analgesia after surgery was decreased, the score for the patient′s satisfaction with analgesia was increased, the knee joint range of motion was increased ( P<0.05), and no significant change was found in the quadriceps muscle strength and incidence of adverse reactions in LB group ( P>0.05). Conclusions:Ultrasound-guided adductor canal block with bupivacaine liposome provides better analgesia than ropivacaine in elderly patients undergoing total knee arthroplasty.