Background
Accurate implant positioning, including rotation, is essential for successful unicompartmental knee arthroplasty (UKA). This study defined the rotational error that would result in medial UKA when using the medial edge of the tibial tubercle (TT) rather than the medial tibial spine for determining tibial component rotation, and in lateral UKA when aligning the anterior edge of the sagittal tibial cut with the lateral edge of the patellar tendon.