Unicompartmental knee arthroplasty (UKA) is the principal surgical alternative to the total knee arthroplasty (TKA) in patients with end-stage unicompartmental tibiofemoral osteoarthritis (OA) of the knee. The current comparative randomized study aims to evaluate the fixation of cemented and cementless designs of GMK-UNI unicompartmental knee prosthesis over a 5-year time period.

The Primary objective is to compare the quality of fixation of cemented and cementless designs of GMK-UNI unicompartmental knee replacement at 2 years of follow-up.

The Secondary objectives include the evaluation of the patient improvement (subjective and objective) using the new Knee Society Score (KSS); the patient's anterior pain following UKA and any eventual patella-femoral disorder; Implant survival rate using the Kaplan Meier analysis; Post-op radiological findings and Adverse Events.

The Primary outcome aims to compare the occurrence of radiolucency's lines (both partial and complete) between the two study groups. Secondary outcomes include New KSS, OKS, Kaplan Meier analysis and stability and fixation of UNI prosthesis.

All patients who meet the inclusion criteria to take part in the current clinical study will be invited to participate before the surgery.

Subjects will be randomized during the screening; half of them will receive the cemented GMK-UNI anatomical UKA and the other half the cementless GMK-UNI anatomical UKA.

Clinical data will be recorded on CRF at those time-points:

• Before the surgery
• During the surgery
• After the surgery at 3 months, 1, 2, 3 and 5 years.

Inclusion criteria:

• Patients with end-stage unicompartmental tibiofemoral osteoarthritis (OA) of the knee that meet the indications for use according to Medacta implants included in this study (on-label use);
• Those suffering from unilateral osteoarthritis or osteonecrosis of the medial compartment;
• Frontal deformity < 10° (evaluated on weight-bearing long-axis x-rays);
• Flexion contracture < 10°;
• Intact ligaments;
• Patients who are willing and able to provide written informed consent for participation in the study. Written informed consent must be obtained prior to the patient's surgery;
• Patient's age over 18 years old;
• Patient with BMI < 40 kg/m2;
• Patients must be willing to comply with the pre and post-operative evaluation schedule.

Exclusion criteria:

• Patients with one or more medical conditions identified as a contraindication defined by the labelling on any Medacta implants used in this study;
• Any patient who cannot or will not provide informed consent for participation in the study;
• Patients who need to undergo lateral unicompartmental knee arthroplasty;
• Patients who need a revision surgery;
• Patients who need a patella-femoral joint prosthesis;
• Patients who had previously undergone high tibial osteotomy or ACL reconstruction;
• Patients with BMI ≥ 40 kg/m2;
• Patients unable to understand and take action;
• Any case not described in the inclusion criteria;
• Patients aged under 18 years;