A knee prosthesis is a biomedical engineering product that replaces the articular surfaces of the patient's natural knee (or any other joint in the respective cases) when they show wear that causes pain, deformity or affects its function. Contrary to what most people may think, only the SURFACE of the joint is replaced, something like rebuilding the "shell" where movement occurs between the three bones that make it up, and not the entire segment of the knee as if it were a "block".

Knee replacement surgery is undoubtedly the most widely performed Orthopedic surgery in the world and with the highest rate of patient and doctor satisfaction, statistics vary in each country, but for example , in Spain the decade of the 90`s went from around 12,500 replacement surgeries, to 25,000 in the following decade, with a knee survival greater than 95% at 10 years (the knee remains unchanged in 95 out of 100 patients operated at 10 years).

The indication for TAR (Total Knee Arthroplasty or Knee Prosthesis) is based on pain, marked functional impotence, and radiological signs of severe joint injury in a relatively sedentary patient, which cannot be detected. control with alternative treatments (oral and injected medications, infiltration into the knee of medications, rehabilitation and physical therapy, etc.).

To establish the indication, it is necessary to integrate multiple variables such as age, associated pathologies (diabetes mellitus, arterial hypertension, kidney diseases, etc.), functional demands (whether the patient is very active or not in his daily life), attitude psychological and technical considerations. It is also important to identify patients at risk of failure (smokers or poor adherence to medical treatment).

Complications range from 5 to 8% of all knee prosthesis surgeries, which means that the rest (95 to 92%) of patients present good to excellent results, regardless of the type of surgery. technique or other factors to consider (weight, previous diseases, surgical skill, type of implant, among others). The most common complications can be:

• Infection, which is the most frequent of all complications and covers a spectrum as broad as superficial skin infections to osteomylitis (bone infection).
• Thrombosis (obstruction by a blood clot of the venous flow).
• Embolism around 1% (a blood clot breaks off to travel in the venous system and cause blood obstruction problems in another organ or system such as the lungs, brain or digestive system).
• Infections (either in the skin or deeper, including the ligament graft).
• Allergic reactions to medications (since if you've never had surgery, the medications being applied are new to your system.
• Failure or loosening of implants: especially if an adequate rehabilitation program is not followed in the postoperative period, weight loss, etc.

Unicompartmental knee prosthesis: It is a very special type of prosthesis in which only part of the knee is replaced and not its entirety, due to overload and wear in a single region (usually the internal region). , the patient must be very well selected and the surgeon who performs the procedure must have experience in it, since this technique is much less tolerant of failures compared to the traditional total prosthesis.

Patello-femoral surface knee prosthesis:This is a prosthesis that treats wear exclusively in the Patello-femoral region of the knee (front area), so the patient, by definition, will only be candidate for this, if the wear presented is solely and exclusively in the region of said area of the knee. The technique is very demanding in terms of the orientation and depth of the bone cuts, so its placement is indicated only by surgeons with great skill and experience in this technique.

Tumor knee prostheses: These are the group of prostheses that are indicated for patients with large bone defects, either due to wear with a marked angulation or fractures or tumors that destroy a large part of the bone tissue of the knee. . They are modular systems (interchangeable) that allow a great diversity of measures and components, therefore they solve cases in which previously no solution would be considered.