The knee joint is the largest of all in the human body. It connects the femur, tibia and patella. It is a double-angled joint reinforced with ligaments and surrounded by a joint capsule. Because of the bandy leg or knock-knee, cartilage wear due to age or defective joint load, alloplastic surgery is required. This is a procedure planned individually for each patient depending on their age, gender or weight. To assess the scale of wear, knee cartilage was scanned using computed tomography. CT scans were processed into a 3D model using Materialize Mimics. Based on obtained bone models, a model of the endoprosthesis was designed using the Catia V5 software. Strength analysis was carried out based on the selection of appropriate materials and theoretically accepted loads.