Abstract:[Objective] To compare the clinical efficacy of unicompartmental knee arthroplasty (UKA) with high tibial osteotomy (HTO) in the treatment of spontaneous osteonecrosis of the knee (SONK).[Methods] Thirty-nine cases of spontaneous osteonecrosis of the knee treated from January 2015 to October 2021 were retrospectively analyzed. According to the results of preoperative doctor-patient communication, 22 were treated with UKA (UKA group) and 17 were treated with HTO (HTO group). Perioperative period, follow-up and imaging data were compared between the two groups. [Results] Both groups were operated successfully. The operation time, post-operation time and total weight-bearing activity time in UKA group were shorter than those in HTO group (P < 0.05). The total length of incision in HTO group was less than that in UKA group (P < 0.05). There was no significant difference in blood loss, wound healing and hospital stay between the two groups (P > 0.05). Follow-up ranged from 12 to 48 months, with an average of (24.69±10.02) months. With the passage of time, the VAS score and WOMAC score decreased and the KSS score increased in the two groups (P < 0.05). The VAS score, WOMAC score and KSS score in UKA group were better than those in HTO group at different time points after operation (P < 0.05). There was no significant difference in knee ROM between the two groups and at different time points within the group (P > 0.05). In terms of imaging, the FTA of UKA group was higher than that of HTO group immediately after operation and at the last follow-up (P < 0.05). The degeneration of lateral ventricle and patellofemoral ventricle in UKA group was lighter than that in HTO group (P < 0.05). There was no significant difference in Insall index between the two groups and at different time points within the group (P > 0.05). [Conclusion] Both UKA and HTO could achieve better clinical efficacy in the treatment of SONK, but the early clinical efficacy of the UKA group was better than that of the HTO group.