Background <p>Isolated lateral osteoarthritis of the knee is a&#xa0;rare condition and mostly coupled with a meniscectomy or lateral osteochondritis dissecans. In cases of grade&#xa0;4 lateral osteoarthritis, preserved cruciate ligaments and functionally intact medial and retropatellar compartments, a&#xa0;lateral unicondylar prosthesis can be implanted. Frontal plane deformities do not represent a strict contraindication.</p> Objective <p>Presentation of the indications, operative techniques and results of lateral unicondylar knee replacement.</p> Material and methods <p>Overview of the literature and personal experience.</p> Results <p>In the literature the survival rate of lateral unicondylar knee replacement is more than 90% after 10&#xa0;years. Fixed bearing systems have proven to be successful on the lateral side, a system with mobile meniscus showed good survival but a high rate of dislocation. Adding a&#xa0;lateral unicondylar prostheses in cases with a medial unicondylar prosthesis in place and lateral development of osteoarthritis show good results.</p> Conclusions <p>With the correct indications, lateral unicondylar knee replacement shows good functional results. The surgical technique is demanding and is clearly different to the medial side. Specific implants designed for the lateral side of the knee joint are recommended.</p>