The mobile bearing unicompartmental knee arthroplasty has shown excellent clinical outcome and survivorship. However, some studies have shown that the patients still had medial knee pain and shown worst the clinical outcome, even though the survivorship was excellent. The medial knee pain after operation was the one cause of revision. The incidence of medial knee pain was 0%-9%. The cause of medial knee pain was overloading on the medial plateau, local inflammation, over hanging of the tibial component and overstretching of the MCL due to the application of excessive polyethylene. Therefore, the tibia in this study was cut with under resection technique for reducing the overloading on the medial tibial plateau. The purpose of this study is to compare medial knee pain between tibial bone cut preservation technique and conventional tibial bone cut technique following mobile bearing UKA.

A randomized control trial study was conducted at Thammasat University hospital, Thailand. The inclusion criteria were patients with medial osteoarthritis (OA) of the knee with an Alhback score of 2, 3 and 4, who were older than 50 years of age, with a range of movement (ROM) > 90°, a varus deformity < 25°, and flexion contracture < 20° who underwent a medial mobile bearing UKA (Oxford UKA; Zimmer Biomet, Inc, Warsaw, IN, USA), performed by a single surgeon. The exclusion criteria were patients with a diagnosis of spontaneous osteonecrosis of the knee (SPONK), intraoperative anterior cruciate ligament (ACL) insufficiency, inflammatory joint disease, gout, post-traumatic arthritis, and primary PF arthritis. The patients were randomized with computer technique into 2 groups, group (gp) I, conventional tibial bone cut technique and gp II, tibial bone cut preservation technique. The baseline patient characteristics included age, sex, site, the Knee Society Score© (KSS) (knee score, pain score, and functional score), Oxford knee score (OKS), KOOS, Kujara score, body mass index (BMI), degree of varus deformity, flexion contracture, genu recurvatum, and range of motion (ROM) were recorded. The patients were followed up at 2 weeks, 6 weeks, 3months, 6months, 1 years, and annually. The VAS ofr medial knee and incidence of medial knee pain were assessed in a blinded fashion by a research assistant at each visit using VAS scale (0-10). The KSS, OKS, KOOS, and Kujara score also were recorded. At each follow-up, the patients underwent AP standing, lateral standing, skyline view, and long-leg radiographs and the component alignment, tibiofemoral angle and joint line of femur and tibia recorded.

Inclusion Criteria:

• medial osteoarthritis of knee

Exclusion Criteria:

• posttraumatic arthritis
• gout
• Rheumatoid arthritis
• anterior cruciate ligament insufficiency
• osteonecrosis of knee