Joint arthroplasty

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Indications for the implantation of a knee prosthesis

Osteoarthritis of the knee (gonarthrosis)

Degeneration of the knee joints is the gradual degradation of the articular cartilage and the underlying bone subcartilage layer. The articular surfaces in the knee are damaged:

the femur and tibia (femo-tibia joint),
kneecap and femur (patellofemoral joint).

As a result of the degeneration process, there is also a secondary disturbance of the structure and function of the capsulo-ligament apparatus and of the soft tissues surrounding the joint.

The pathogenesis of osteoarthritis of the knee is multifactorial - the process of cartilage destruction may be caused by the following factors:

biomechanical - varus or valgus of the knees, excessive body weight, competitive sports, chronic untreated intra-articular injuries,
inflammatory - inflammatory diseases affecting the locomotor system (e.g. rheumatoid arthritis, history of infectious arthritis),
genetic - diseases associated with physico-chemical disorders of the articular cartilage (crystallopathies, arthropathies accompanying other systemic diseases).
The main symptom accompanying gonarthrosis is pain in the knee joints, most often occurring when walking, running, going up and down stairs or doing squats. In the case of degeneration of the patellofemoral joint, pain in the front of the knee while standing up after prolonged sitting for a long time is characteristic (the so-called kinomancer symptom). You may hear creaking noises as you bend and extend your knees. Knee overloads often cause recurrent exudation, the formation of the so-called Baker's cyst in the popliteal fossa. The contour of the knee is deformed, the mobility of the joint is gradually limited and the strength of the thigh muscles weakens, which negatively affects the quality of gait and comfort of life. 

Other indications for knee arthroplasty

inflammatory diseases that degrade the knee joint,
sterile bone necrosis involving articular surfaces,
joint damage in people with hemophilia,
post-traumatic knee deformities,
tumors in the knee joint requiring resection.

Qualification for knee prosthesis surgery

Knee arthroplasty is performed when conservative treatment or other surgical treatment methods (e.g. knee arthroscopy or knee osteotomy) would be ineffective and the symptoms of pain and restriction of mobility significantly reduce the patient's quality of life. Knee arthroplasty is an irreversible procedure (permanently removing the patient's own joint), usually performed in people over 50 years of age.

In order to accurately qualify a patient for an endoprosthesis procedure, an orthopedic surgeon should rely on the correlation between clinical symptoms and radiological symptoms of knee joint degeneration. The doctor analyzes the X-ray image of the knee joints, on which he assesses the degree of destruction of the articular surfaces and bone deformities. In the case of traumatic deformities, it may be necessary to perform computed tomography or magnetic resonance imaging.

Types of knee endoprostheses

Artificial components of the knee prosthesis are designed to replace the removed articular surfaces or part of them. Total prostheses are the most common, although many patients benefit from single-compartment prostheses or other implants locally placed in the joint. The components of the knee prosthesis can be made of metal alloys, ceramics or polyethylene. Designs of individual types of endoprostheses are created on the basis of research on the biomechanics of the knee joint - data from biomechanical models describing the pattern of knee loads during various body positions (standing with both foot and single leg) or performing specific activities (walking, descending stairs) are used. The Dworska Hospital uses implants from leading, proven all over the world manufacturers. The surgeon proposes a type of knee prosthesis that will best fulfill its role depending on the degree of damage to the knee and the patient's level of activity.

Total prosthesis
Total knee prosthesis consists of:

Femoral element - placed on the distal socket of the femur,
Tibial element - placed on the proximal epiphysis of the tibia,
The articular surface of the patella - an insert usually made of polyethylene (rarely used).

One-compartment and two-compartment endoprosthesis

In the case of damage to the articular cartilage of only one of the knee compartments (e.g. medial or lateral compartment), a prosthesis can be applied to one of the femoral condyles and the corresponding part of the tibia. The use of a single-compartment prosthesis enables the preservation of the remaining knee structures (e.g. cruciate ligaments) and is a procedure that is less traumatizing to the knee joint. Two-compartment prosthesis involves the replacement of the medial and lateral compartment without placing the patellar prosthesis.

Revision prosthesis

The knee prosthesis wears out just like a natural joint, so sometimes it has to be replaced with a new one - this procedure is then called realloplasty. Current knee prostheses last 10-17 years, depending on the min. weight and activity of the patient. The necessity to re-implant an endoprosthesis results most often from the wear of the prosthesis components or the loss of its stability in the bone bed. In general, the indications for realloplasty include:

Aseptic loosening of the knee prosthesis (without infection),
Mechanical damage to the knee prosthesis,
Inflammation of the tissues around the knee prosthesis as a result of infection - this is called septic loosening of the implant.
Revision prosthesis shafts are usually longer and may contain additional elements to fill bone defects. Moreover, the femoral and tibial parts can be connected with each other with a special connector for better stabilization of the artificial knee.

Arthrosurface surface prosthesis

Surface prostheses are a good solution for people aged 40-65 with focal cartilage damage, for whom biological reconstructions will no longer be effective. It is a bridge method between treatments using biomaterials and the ability of tissues to self-regenerate (e.g. hyaluronic acid or collagen membranes, special gels) and the classic arthroplasty procedure. The surgeon covers only the local defect in the cartilage of the thigh or tibia with the prosthesis, leaving all other parts of the joint intact. Thanks to this, we preserve the original anatomy and biomechanics of the knee joint, and at the same time eliminate the cause of knee pain, allowing the patient to quickly return to activity to a much greater extent than possible with half or full prostheses.

The condition for the success of the operation is the preservation of the remaining structures of the knee joint, the lack of extensive bone deformation or significant disturbances of the knee alignment (large varus or valgus). If necessary, the surface prosthesis can be replaced with the primary endoprosthesis - less invasive in relation to the revision prosthesis.

Knee prostheses - types of connections

The femoral component and the tibial component of the total prosthesis may be interconnected in various ways depending on the ligaments preserved and the degree of knee instability. We distinguish endoprostheses:unbound - the tibial and femoral elements are not related to each other, they require good ligamentous capacity of the knee - the most commonly used standard,
semi-connected (condylar) - elements are partially connected with each other, used in the case of failure of one collateral ligament,
hinge-rotational - they have a full hinge connection of the femoral and tibial elements, used in the case of severe ligamentous insufficiencies of the knee, disorders of the joint axis (varus, valgus), allow smaller flexion and extension, as well as rotational movements.
hinged - prosthesis elements connected by a hinge, allow only limited flexion and extension movements, very rarely used.
Knee prostheses may retain the natural posterior cruciate ligament (so-called cruciate retaining prostheses) or have an element that stabilizes and replaces the function of the posterior cruciate ligament (PS prostheses, posterior substituting).

Fixed Bearing and Mobile Bearing prostheses

Due to the mobility of the polyethylene insert, endoprostheses are divided into:

Fixed bearing - the polyethylene insert is firmly attached to the tibia,
Mobile bearing - the polyethylene insert can rotate in relation to the tibial element, reproducing more precisely the biomechanics of the tibia's movement in relation to the thigh.

Cement and cementless endoprostheses

Knee implants can also be divided according to the method of attachment:
Cement - embedded knee joint prosthesis connects to the bone thanks to the use of "glue" - acrylic bone cement,

Cementless - the bone grows directly into the porous surface of the prosthesis, the use of bone glue is not necessary. This type of prosthesis requires a very good, strong bone tissue from the patient.

Preparation for the procedure

Rehabilitation preparation before surgery:

reducing the contracture of the soft tissues of the knee - this will make it easier for surgeons to correctly implant the endoprosthesis,
improvement of the muscle strength of the lower limb - the greater the muscle strength before the procedure, the easier it will be to rebuild it during postoperative rehabilitation,
getting acquainted with the exercises that will be performed after the endoprosthesis surgery,
general strengthening of the musculoskeletal system - it will positively affect the comfort of functioning in the postoperative period,
learning to walk on crutches,
body weight normalization.
Preparation related to anesthesia and surgery:

cure any infections, e.g. chronic sinusitis, urinary tract inflammation and cure tooth decay - prevention of complications in the form of infection of the endoprosthesis and its secondary loosening after surgery,
vaccination against hepatitis B,
performing tests: blood count and electrolytes, coagulation system, sugar level, chest X-ray, general urine test, heart ECG, blood group determination,
consultation with specialists in the treatment of chronic diseases,
final qualification for the procedure carried out by an anaesthesiologist, taking into account all the above factors.

The course of the knee prosthesis implantation

The surgery is performed under epidural anesthesia. The surgeon uncovers the part of the joint to be replaced and prepares it for the replacement of the prosthesis. The cut goes vertically down the front of the knee and the patella is moved to the side to allow comfortable access to the tibial joint. In total arthroplasty, the operator cuts the distal femoral and proximal ends of the tibia using special instrumentation. The procedure must be performed with the greatest precision so that the implant is placed in the correct orientation. Prior to the final fixation of the prosthesis, the surgeon checks its alignment and the alignment of the femoral and tibial components as the knee moves. The back surface of the kneecap can be covered with a polyethylene wrap and then the kneecap is put back in place at the front of the knee. The procedure ends with the closure of the wound leaving the drains to drain the blood.

Rehabilitation after knee prosthesis

Exercises after knee prosthesis are performed under the supervision of a physiotherapist and begin on the first day after the endoprosthesis surgery. These are simple breathing exercises, anticoagulant exercises, isometric exercises for the operated limb and other active parts of the body. After removing the drains, the operated leg can be placed on a special splint that performs a very slow passive movement of knee flexion and extension. This is the first element of the prevention of arthrofibrosis, i.e. fibrosis of the tissues of the joint limiting its mobility. In the Dworska Hospital, in order to ensure the patient's comfort, a Game Ready device is used, which at the same time cools and exerts optimal pressure on the operated area. Thanks to this, the swelling after the knee replacement surgery is much smaller, the discomfort during the movement of the limb is minimal, which allows for faster introduction of active knee exercises.

On the 2-3rd day after the procedure, the patient learns to get up and walk on crutches. A physiotherapist is present for all activities, who protects and makes sure that every change of position is safe for the patient. The therapist also gives tips on how to proceed at home - including the position of the operated knee, which should be avoided in order to maintain the good condition of the prosthesis. The patient leaves the hospital 5-7 days after surgery and reports for inspection on days 10-14 after surgery, when the sutures are removed. The next stages of rehabilitation after endoprosthesis include: postoperative scar massage, exercises for the knee joint to improve the range of motion, exercises to strengthen the muscles controlling the movement of the knee, balance exercises and learning how to properly weight the limb (when allowed by the doctor). Post-surgery knee exercises should be performed regularly, for at least 3 months. A knee brace is not necessary after arthroplasty.

Complications after knee arthroplasty

Complications after the endoprosthesis implantation procedure are frequent in the case of frequent patient occurrence and correction of the implementation of the recommendations. However, everyone has the possibility of their occurrence, including:

soft material fibers limiting movement, lack of rehabilitation and soft material,
deep lower venous thrombosis,
painful, without her mobilization, with the first points - with the lack of her mobilization,
blood-derived blood of the knee prosthesis and its secondary loosening - the generation of a rolling infection,
dislocation - laying under the condition of prohibition provided that the dance arrangement or bankruptcy.

Life of the endoprosthesis

Contrary to the tissues of a natural joint, endoprosthesis materials do not have the ability to adapt to the transferred loads. Good alignment of the prosthesis during surgery reduces the risk of overload zones that could lead to premature wear or loosening of the knee prosthesis components. It is worth noting that the degree of asymmetry in the load on the prosthetic components depends on the total biomechanical axis of the lower limb, including the foot. Additionally, the distribution of loads on the prosthesis components dynamically changes as the knee moves in different activities. In the case of very severe knee deformities and accompanying untreated foot defects or hip disorders, it may be difficult to obtain the optimal axis of the artificial knee. The risk of endoprosthesis damage or loosening is additionally higher in people with poor bone quality, metabolic diseases and obesity. In order to keep the knee prosthesis in good condition, one should avoid crossing the legs, kneeling, squatting, and practicing sports with a large component of running and jumping. The recommended activity is back swimming or riding a stationary bike with slight resistance.

The average service life of a knee replacement is approximately 12-17 years. Total arthroplasty is not recommended for people under 45 due to the inevitable need to replace the implant again.

Important information

Frequently asked questions about knee arthroplasty: