Background. In determining the indications for unicondylar endoprosthesis of the knee joint the literature practically does not cover the results of such interventions in knee osteoarthritis in patients with chondrodysplasia. The purpose of our report was to publish our observation of the long-term results of unicondylar endoprosthesis of the knee joint in a patient with knee osteoarthritis due to chondrodysplasia. Material and methods. We operated on a patient with chondrodysplasia who came to the clinic at the age of 28 with complaints of pain in the right knee joint during walking, “clicking” and joint swelling. The radiological and magnetic resonance examination results of the right knee determined the presence of an area of aseptic necrosis of the medial femoral condyle. Considering the concordance of lower limb axis disorders, it was decided to perform unicondylar arthroplasty with preservation of the preoperative varus deformity to maintain the motor stereotype's compensation state. Results. In the postoperative period, there were no complications in wound healing, the rate of recovery of movements corresponded to similar indicators in patients with knee osteoarthritis of other etiologies after similar interventions, and the patient was discharged from the hospital on the sixth day after surgery with the preoperative range of motion in the operated joint. At the examination 10 years after the operation there were no complaints from the operated knee joint, the movements in the operated joint remained in the same range, and the patient moved without additional support with full load on the operated limb. Conclusions. Our results indicate the appropriateness of unicompartmental knee arthroplasty in patients with knee osteoarthritis secondary to.