Arthroprosthetic surgery can become the only valid treatment solution for various pathologic diseases that affect the knee joints; it is particularly advisable in case of OSTEONECROSIS, RHEUMATOID ARTHRITIS or in TRAUMATIC CONSEQUENCES. The vast majority of these operations is performed because of the presence ofPRIMARY ARTHROSIS. Arthrosis is a progressive wearing process of the cartilaginous components of the joints leading to a progressive deformation of the ends of the joint. It causes pain, frequent swelling of the joint and serious movement impediments. Arthrosis tends to worsen over the years and with the use of the joint. The localisation of the arthrosis process at knee level is one of the most frequent and most invalidating conditions because knee joints have a fundamental role in the support of body weight while standing and walking. Arthroprosthetic surgery consists in the resection of deformed components of the joints with no cartilage left, and in their replacement with artificial coatings made of metal alloys and synthetic plastic materials. KNEE PROSTHESIS The aim of this operation is to make the joint hurt less or not at all, to put it in good axis and to give it sufficient mobility range in order to allow walking. However, it is important to remember that, contrary to human body tissues, prosthesis do not have any biological maintenance power and that they will eventually wear out. The better the joint is used, the slower such wearing process will be. Therefore, it is fundamental to take good care of the operated knee, follow simple behavioural rules and take some precaution measures in advance: it is important to avoid traumatisms and useless stress, standing for a long time, running, potentially traumatic sports activity and any particularly physically demanding job. It is important not to gain weight because this could speed up the wearing process. Maintaining a good muscular tone can help the new joint work better for a longer time. A blood pre-deposit is highly recommended before the operation (a certain amount of blood is taken from the patient) so that it is available during the operation (self-blood transfusion) should the need arise to compensate losses due to the operation. Moreover, we suggest to buy a pair of elastic socks that the patient will wear after the operation to decrease the risk of deep vein thrombosis. The kind of anaesthesia used can be either general or spinal: the choice will be made by the anaesthetist in line with the patient's general condition. In the first few hours before and after the operation, the patient will have to follow an anticoagulant therapy (in order to decrease the risk of phlebothrombosis), an antibiotic therapy (to decrease risk of infections), and an analgesic therapy (only if necessary). After the operation, the patient will have one or two rubber drainage tubes coming out of the operated knee the purpose of which is to allow the down-flow of blood from the joint. On the 1st day after the operation, the patient is able to sit up on the bed and stretch out his/her legs. Usually, on the 2nd day, the drainage tubes are removed and the wound medicated. On the 3rd day, the patient starts the physiotherapy supported by the physiotherapist and a medical device to help him/her with the first movement attempts. After each physiotherapy sessions, an ice bag is placed on the operated joint. Such applications are repeated two or three times every day. Between the 4th and the 6th day, the patient starts walking supported by a walker. From the 7th day, the patient is usually able to sit up and eat normally at a table. Re-education continues in order to improve movement abilities and to make the patient gradually capable of walking on his/her own again. Gradually, the patient starts using crutches and, when he can walk correctly, the patient can to leave the hospital (this usually happens between 8 and 10 days after the operation). After leaving the hospital, the patient should be followed by a physiotherapist for the following few weeks in order to regain full movement of the knee and to make sure that the patient exercises correctly. Out-patients check-up examinations are performed : a few days after leaving the hospital to remove stitches (in the case this did not happen during hospitalisation); 45 days after the operation with X-rays to the knees in the two standard projections (front-back and lateral). After this, if the deambulation is correct and the muscular tone is good, the specialist may stop the use of crutches; a year after the operation with new X-rays to the knees in front-back projection while standing , and to the operated knee in standard lateral projection; every following year, with new X-rays (see above). POSSIBLE COMPLICATIONS LINKED TO THE ARTHROPROSTHETIC SURGERY OF THE KNEE In the past few years, the arthroprosthetic surgery of knee has definitely seen an improvement of the prognosis aspects, thanks to advanced techniques and to the continuous improvement of the material used; although once considered to be a high risk surgical operation, today it has become a routine for the majority of orthopaedic Operative Units. However, in order to provide correct and adequate information to the patients, it is also necessary to mention the possible complications (both intra- and post- operation) that, although not frequently, might arise. PROMINENT AND PERSISTENT SWELLING: this is a minor complication that can be solved through constant ice applications and increased rest; sometimes, it might be necessary to drain the liquid with a syringe (Arthrocentesis). PHLEBO-THROMBOSIS OF THE LEG: it indicates the inflammation of the veins of the operated leg (seldom the other one) which is revealed by a large swelling of the foot and of the leg itself, a strong sense of heaviness of the limb and calf pain. In order to decrease the occurrence of such a complication, it is necessary to carefully follow the heparin therapy recommended when discharged from the hospital, start the rehabilitation therapy as soon as possible and follow it consistently and, where suggested, wear the anti-thrombosis socks. PULMONAR EMBOLISM: it indicates the detachment of a thrombus that has developed in one of the veins as a consequence of the previously described complication. The thrombus reaches the lungs and causes chest pain, difficulties in breathing, cough, sometimes bronchial catarrh containing a little bit of blood. This is a very dangerous complication that requires immediate hospitalisation in an internal medicine ward. In order to prevent such complication from arising, the same preventive measures for deep vein thrombosis need to be followed. INFECTION OF THE ARTHROPROSTHESIS: : the signs of its acute form are a very high fever, strong pain in the operated knee which feels particularly swollen and hot. The signs of its sub-acute form, instead, are a light but constant fever, strong pain in the operated knee which appears swollen and very hot. This complication is very important but sometimes it can be solved with a new heavy-dose antibiotic therapy to be followed for a few weeks. If this treatment does not lead to any improvement, then the it might become necessary to remove the prosthesis and place rubber tubes for the constant washing of the joint, or even to perform an arthrodesis surgery (blocking of the joint) thus compromising the functionality of the entire limb. ASEPTIC DETACHMENT OF THE PROSTHESIS: this is usually a late complication; this term indicates a progressive detachment of the components of the prosthesis from the bone, and it is not a consequence of infection. If it is very extended, it may require the re-implant of a new prosthesis. PARTIAL LOSS OF MOBILITY: when it happens, it usually concerns just a few degrees; the best way to prevent it is a good physiotherapy. If the loss is more serious, then a new operation to correct such loss of mobility may be necessary.