Background <p>Total knee arthroplasty (TKA) is an effective treatment for end-stage knee osteoarthritis, but postoperative pain and delayed recovery remain challenges. This study aimed to evaluate the effects of hypobaric unilateral fine-needle spinal anesthesia combined with multimodal analgesia (MMA) on postoperative recovery in TKA patients.</p> Methods <p>A randomized controlled triple-blind trial enrolled 118 patients scheduled for TKA between January 2022 and June 2023. Patients were divided into three groups: hypobaric fine-needle spinal anesthesia (Group A, <i>n=</i>40), isobaric fine-needle spinal anesthesia (Group B, <i>n=</i>39), and hypobaric spinal-epidural combined anesthesia (Group C, <i>n=</i>39). Outcomes included puncture success rates, puncture time, maximum active knee flexion angle, breakthrough analgesia frequency, statistical test and complications.</p> Results <p>No significant differences were observed in puncture success rates. However, Group C had a significantly longer puncture time than Groups A and B. Group B showed a lower maximum active knee flexion angle on postoperative day 1 compared to Groups A and C. Group C had a higher incidence of low back pain and headache within 7 days. Postoperative pain scores (NRS) were significantly lower in Group A at all time points.</p> Conclusions <p>Hypobaric fine-needle spinal anesthesia (Group A) demonstrated superior performance in puncture time, postoperative mobility, and complication rates, making it a preferred anesthetic strategy for TKA.</p> Trial registration <p>Chinese Clinical Trial Registry (ChiCTR2500100428). Registered on 9 April 2025. Retrospectively registered.</p>