There is obviously a lack of evidence regarding the risk-benefit ratio of a thigh tourniquet in unicondylar knee arthroplasty (UKA). This refers to many possible outcome criteria like operating time, blood loss, quality of prosthesis fixation in the bone, adverse events, radiographic result, clinical score outcome, easy of rehabilitation etc. It is not appropriate to rely on findings from the field of total knee arthroplasty.

It is the aim of the current study, to clarify the role of a thigh tourniquet during UKA with regard to component fixation quality, component positioning and sizing, clinical outcome and rehabilitation process.

Patients scheduled for routine UKA implantation due to osteoarthritis or osteonecrosis in the medial compartment will be considered for participation.

Patients are then randomized for surgery with or without tourniquet. After an anteromedial Quad-Sparing approach the UKA procedure itself is then carried out, as suggested by the manufacturer. For both groups puls lavage and meticulous drying is applied before cementing.

The following outcome parameters are assessed: 1)radiographic cement mantle thickness, 2)component position & sizing, 3)diolucencies, 4)score outcome and 5)parameters of early Rehab.

Inclusion Criteria:

• waiting list for unicondylar knee arthroplasty

Exclusion Criteria:

• failed upper tibial osteotomy,
• insufficiency of the collateral or anterior cruciate ligaments,
• a fixed varus or valgus deformity (not passively correctable) above 15°,
• a flexion deformity greater than 15° and 5) rheumatoid arthritis. In addition - with regard to the scope of the current study - further exclusion criteria will be
• intake of medicinal anticoagulation prior to surgery
• liver dysfunction / coagulation dysfunction
• peripheral arterial obstructive disease.