THE BONE & JOINT JOURNAL 126 B. P. Chalmers, E. Goytizolo, M. D. Mishu, G. H. Westrich From Hospital for Special Surgery, New York, New York, USA Correspondence should be sent to G. H. Westrich; email: WestrichG@HSS.EDU © 2021 The British Editorial Society of Bone & Joint Surgery doi:10.1302/0301-620X.103B6. BJJ-2020-1950.R1 $2.00 Bone Joint J 2021;103-B(6 Supple A):126–130.  The Knee SocieTy Manipulation under anaesthesia after primary total knee arthroplasty MiniMal differences in intravenous sedation alone versus neuraxial anaesthesia Aims Manipulation under anaesthesia (MUA) remains an effective intervention to address restricted range of motion (RoM) after total knee arthroplasty (TKA) and occurs in 2% to 3% of prima- ry TKAs at our institution. Since there are few data on the outcomes of MUA with different anaesthetic methods, we sought to compare the outcomes of patients undergoing MUA with intravenous (iV) sedation and neuraxial anaesthesia. Methods We identifed 548 MUAs after primary TKA (136 IV sedation, 412 neuraxial anaesthesia plus IV sedation) from March 2016 to July 2019. The mean age of this cohort was 62 years (35 to 88) with a mean body mass index of 31 kg/m 2 (18 to 49). The mean time from primary TKA to MUA was 10.2 weeks (6.2 to 24.3). Pre-MUA ROM was similar between groups; overall mean pre- MUA extension was 4.2° (p = 0.452) and mean pre-MUA fexion was 77° (p = 0.372). We com- pared orthopaedic complications, visual analogue scale (VAS) pain scores, length of stay (LoS), and immediate and three-month follow-up knee RoM between these groups. Results Following MUA, patients with IV sedation had higher mean VAS pain scores of 5.2 (SD 1.8) compared to 4.1 (SD = 1.5) in the neuraxial group (p < 0.001). The mean LOS was shorter in patients that received IV sedation (9.5 hours (4 to 31)) compared to neuraxial anaesthesia (11.9 hours (4 to 51)) (p = 0.009), but an unexpected overnight stay was similar in each group (8.6%). Immediate-post MUA ROM was 1° to 121° in the IV sedation group and 0.9° to 123° in the neuraxial group (p = 0.313). Three-month follow-up ROM was 2° to 108° in the IV sedation group and 1.9° to 110° in the neuraxial anaesthesia group (p = 0.325) with a mean loss of 13° (ranging from 5° gain to 60° loss), in both groups by three months. No patients in either group sustained a complication. conclusion iV sedation alone and neuraxial anaesthesia are both effective anaesthetic methods for MUA after primary TKA. Surgeons and anaesthetists should offer these anaesthetic techniques to match patient-specifc needs as the orthopaedic outcomes are similar. Also, patients should be counselled that RoM following MUA may decrease over time. cite this article: Bone Joint J 2021;103-B(6 Supple A):126–130. introduction Stifness after primary total knee arthroplasty (TKA) remains a common concern. 1,2 Manip- ulation under anaesthesia (MUA) remains the frst-line intervention for stifness after primary TKA. 1,2 The rate of MUA after primary TKA that has been reported ranges from 1% to 5%, 1-12 with most studies reporting good intermediate and long-term outcomes. 9-12 A number of risk factors for MUA have been identifed, including preoperative diminished range of motion, poorly controlled postoperative pain, spinal deformity, prior surgery, smoking, type of venous thromboembolism chemoprophy- laxis used, young age, male sex, and others. 9-18 However, while intravenous (IV) sedation alone and neuraxial anaesthesia are the most common forms, there are few studies examining the safest and most efcient method of anaesthesia for