Osteoarthritis (OA) of the knee can occur as single, bi-, or tri-compartment disease. When a patient presents with single-compartment OA, there are several viable surgical treatment options depending on age and desire of activities. Isolated lateral compartment knee OA is less common than isolated medial-sided OA. A unicondylar knee arthroplasty (UKA) is an excellent option to be considered for the young, active, arthritic knee to successfully allow return to full sport activities. While the lateral UKA is technically more demanding than the medial UKA, both have reproducible results. The anterior cruciate ligament (ACL)-deficient knee adds another layer of complexity and historically has been a contraindication to UKA; however, recent reports show success of medial and lateral UKA in the setting of ACL deficiency and isolated single compartment knee OA.