The purpose of this study is to explore the effects of the Oxford unicompartmental knee arthroplasty on two groups of patients, namely one with genu recurvatum before the procedure and one without. Specifically, this study compare the number of occurrences of postoperative genu recurvatum and the postoperative hyperextension angles among the patients. Additionally, the knee scores, the pain scores, and the functional scores for the two groups of patients are compared.

Materials and methods: This study prospectively followed 104 patients (114 knees) who had been treated with cemented minimally invasive surgery unicompartmental knee arthroplasty and had had a minimum of 24 months of follow-up. The patients were divided into two groups: those without preoperative genu recurvatum (85 patients; 94 knees) and those with preoperative genu recurvatum (19 patients; 20 knees). The incidence of the postoperative genu recurvatum, the postoperative hyperextension angles, the knee scores, the pain scores, and the functional scores were recorded and compared between two groups..

The patients in both groups were applied with cemented Oxford unicompartmental knee arthroplasty with the same surgeon. The all patients were performed surgery with minimally invasive surgery technique. The gender, site, range of motion, alignment of prosthesis, operative time, blood loss, and posterior slope of tibial component also were recorded and compared between two groups. The incidence of postoperative genu recurvatum, gender, and site were computed using Fisher's exact test. The hyperextension angle, knee score, pain score, functional score,range of motion, alignment of prosthesis, posterior slope of tibial component, operative time, and blood loss were compared with student t-test.

Inclusion Criteria:

• The medial OA knee with older than 40 years of age, ROM greater than 90°, varus deformity less than 25°, and flexion contractures less than 20°

Exclusion Criteria:

• patients who were diagnosed spontaneous osteonecrosis of knee (SPONK), patients with intraoperative ACL insufficiency, post traumatic arthritis, gouty arthritis, inflammatory joints.