Abstract:[Objective] To compare the clinical outcomes of three tibial rotation positioning techniques in Oxford unicompartmental ar- throplasty (UKA) . [Methods] From January 2018 to January 2020, 59 patients with medial compartment osteoarthritis of the knee were en- rolled into this study and were randomly divided into three groups. All the patients received UKA, with tibial rotation positioning by anteri- or superior iliac spine (ASIS) in 19 patients, substitute anteroposterior line (sAP) in 20 patients, and anatomical tibial axis (ATA) in 20 pa- tients. The 3 groups were compared regarding to perioperative, follow-up and radiographic documents. [Results] All the patients in the 3 groups had UKA performed smoothly without serious complications. Although there were no significant differences in terms of operation time, incision length, intraoperative blood loss, time to resume walking, hospital stay and incision healing among the 3 group (P>0.05) , the anteromedial protrusion of the liner was noted in 5 cases of ASIS with a displacement of (2.07±0.52) mm , whereas 2 cases in the sAP group with a displacement of (1.93±0.38) mm, and none of the ATA group, which proved statistically significant (P<0.05) . As time went during the follow-up lasted for (14.82±1.05) months on average, the KSS clinical and functional scores significantly increased in all the 3 groups (P<0.05) . Although there were no statistically significant differences in preoperative KSS clinical score and functional score among the three groups (P>0.05) , the sAP group and ATA group was significantly superior to the ASIS group in KSS clinical score at 12 months post- operatively (P<0.05) . Radiographically, the ASIS group had significantly greater external rotation angle of the tibial component than the sAP group and the ATA group postoperatively (P<0.05) . No dislocation or loosening of the prosthesis was found in anyone of the 3 groups during follow-up. [Conclusion] The external rotation of tibial prosthesis positioning by sAP line and tibial anatomical axis in Oxford UKA is simple and reproducible, which is beneficial to the recovery of postoperative joint function.