Lateral unicompartmental knee arthroplasty (UKA) outcomes have been inferior to those described after medial UKA. Inaccurate implant positioning and mechanical axis malalignment appear to be the most common technical errors. Rare studies or failure identification on lateral UKA are currently presented in the literature. We describe the utilization of computer-assisted lateral UKA placement for lateral knee osteoarthritis with a valgus malalignment of 10°. Navigation allows for a dynamic intraoperative visualisation of the mechanical axis, as well as for accurate component positioning and overall postoperative limb alignment. The systems allow the knee position to be captured with appropriate tension in extension and flexion prior to making definite cuts. Postoperatively, no instabilities occurred with a precise component placement. Navigation can be used in rare cases for lateral UKA.