Abstract:[Objective] To compare the mid-term clinical outcomes of lateral unicompartmental knee arthroplasty (UKA) in the treatment of post-meniscectomy knee osteoarthritis (PMKO) versus primary knee osteoarthritis (PKOA). [Methods] A retrospective analysis was conducted on 327 patients who underwent initial lateral UKA due to osteoarthritis of the lateral compartment from March 2013 to March 2019. Based on whether they had a history of meniscectomy, the patients were divided into two groups. Of them, 38 patients were fall in the PMKO group (meniscectomy group), subsequently, 38 patients were selected to be included in the PKOA group (non-meniscectomy group) by paired 1∶1 according to age, gender, and side affected. The documents were compared between the two groups regarding to general information, perioperative period, clinical follow-up, and imaging data. [Results] The PMKO group was significantly greater than the PKOA group in terms of ratio of trauma history [(yes/no), (36/2) vs (0/38), P<0.001] and preoperative Q angle [(15.3±3.0)° vs (12.8±3.3)°, P<0.001], and the severity preoperative lateral compartmental Kellgren-Lawrence (K-L) classification [0/1/2/3/4, (0/0/1/13/24) vs (0/0/3/21/14), P=0.020], while the former proved significantly less than the latter in term of preoperative knee flexion contracture angle [(5.6±3.9)° vs (8.2±4.5)°, P=0.014]. There was no statistically significant difference between the two groups in terms of surgical time, total incision length, intraoperative blood loss, postoperative drainage volume, incision healing, and hospital stay (P>0.05). The male got significantly longer asymptomatic survival period than the female after meniscectomy in the PMKO group (P<0.05). All patients in both groups were followed up for (63.2±24.6) months on an average, and no revision surgery happened in anyone of them. There were no statistically significant differences in VAS, OKS score, ROM, femorotibial angle (FTA), medial proximal tibial angle (MPTA), and posterior tibial slope angle (PTSA) between the two groups at the latest follow-up (P>0.05). [Conclusion] The mid-term clinical consequence of lateral UKA for knee lateral compartmental osteoarthritis is satisfactory. The history of lateral meniscus resection has no significant impact on the postoperative outcome of lateral UKA.