Knee prosthesis

An artificial knee joint is used when the surface of the knee is so worn down that the gliding joint no longer functions properly.

If the pain is causing severe enough restrictions to the patient’s personal or professional life, the use of a knee prosthesis may be considered.

Whether a partial or total joint prosthesis is used depends on how far the osteoarthritis has progressed.

Symptoms

Typical symptoms include pain when climbing stairs or when doing movements that involve squatting. Severe exertion-induced pain occurs during exercise, especially when doing sports with fast stop-and-go movements (e.g. tennis, basketball or football). Symptoms also occur when the knee joint is kept in one position for a long period of time, such as when driving a car or during a long flight.

Causes

Osteoarthritis of the knee is often triggered by damaged articular cartilage or meniscus injuries.

Where the patient has advanced osteoarthritis of the knee (gonarthritis), resulting in damage to the joint and restricted movement, the use of a knee prosthesis (partial or total joint replacement) is required.

Diagnosis

Before deciding whether the use of an artificial knee prosthesis is the right method of treatment, an examination is carried out in which X-rays and MRI images are taken.

Treatments

A knee joint prosthesis (an artificial knee joint) is used to enable the patient to regain their freedom of movement, allowing them to walk properly again and to live without pain. However, an artificial joint will never completely replace the original knee joint. It can be noisy and, under extreme exertion, it will wear out over time.

Various knee prostheses are used today, but the surgeon can only decide which type of knee prosthesis to use once the procedure is under way. That is because it is only during surgery that they are able to see how severely the knee joint is damaged.

Of all the prostheses available, the method proven to have the best results is knee joint resurfacing, which focuses on the soft tissue in the joint.

If this method is used, the surgery mainly involves the collateral ligaments of the affected knee. During this procedure, a soft tissue pressure gauge is used to determine the force of the inner and outer ligaments in various positions. Scarred collateral ligaments are treated until the affected knee is straight again, with the same amount of force applied to the inner and outer ligaments.

This procedure allows the surgeon to tailor the artificial knee prosthesis to the needs of the individual patient, focusing on the various changes in the knee joint resulting from the osteoarthritis.

The surface replacement is only inserted once the leg is straight again, due to the equalisation of the collateral ligaments. This ensures that the new knee joint prosthesis is evenly loaded.

The soft tissue-focussed method is used in the following procedures:

  • Partial resurfacing (sled prosthesis, patellofemoral joint replacement): Only half of the joint surface needs to be replaced and the patient’s own cruciate ligaments are preserved.
  • Complete resurfacing (knee prosthesis): The entire joint needs to be replaced.
  • Revision prosthesis (hinged/guided knee prosthesis, complete knee joint replacement): The collateral ligaments no longer function, the bone quality is poor (osteoporosis); there are significant misalignments or an existing prosthesis needs to be replaced.

Aftercare

Following the procedure, patients spend an average of one week in the clinic. The day after the operation, you will start a course of movement therapy in the form of daily exercises.

After about four days you can try taking your first steps using crutches. For the first four to six weeks, crutches are an important part of gait training.

The patient has two to three physiotherapy sessions a week, which is important for coordination, building muscle and improving the stability of the knee.

FAQs

Which is the best type of knee prosthesis?

The type of knee prosthesis that is best suited in the individual case will be clarified during the preliminary examinations. However, the exact condition of the joint only becomes fully visible during the operation. It is therefore possible that, at this point in time, the surgeon deviates from the course of the operation previously discussed. You can find out more about selecting the right prosthesis in this specialist article. Contact us for a personal consultation.

How long does a knee prosthesis last?

Although we might want them to last a lifetime, it’s important to be aware that an artificial knee joint is only ever a temporary solution. That is not down to the prosthesis itself, but because the ageing process continues and can have a significant impact on the stability of the artificial joint. Nowadays, we expect the average prosthesis to last for at least ten to fifteen years. Patients who have had an artificial knee joint inserted at a young age should expect to have another replacement or revision operation later in life. However, given the remarkable advances in both surgical techniques and the development of new artificial joints, this is highly feasible. There are several factors that may negatively impact the lifespan of an artificial knee joint. Ultimately, these lead to a loosening of the artificial knee joint, which results in increased exertion-induced pain and an unsteady gait. In the advanced stage, this requires a revision of the prosthesis.

Exertion

The mechanical causes that negatively impact the lifespan of an artificial joint include increased stress on the joint, as well as deterioration of the original anchoring of the joint in the bone. The activities you partake in play a decisive role in over-exerting the joint. The more active you are and, above all, the more sports you partake in that apply pressure to the joint, the more the anchorage of the lower leg component will be stressed by the artificial joint. Excessive strain can also be the result of suboptimal placement of the artificial joint. Furthermore, the original anchorage of the artificial knee joint in the bone can deteriorate slowly due to advancing osteoporosis, or quickly due to a fall-induced fracture. Both cases lead to a loosening of the artificial knee joint.

Infections

Infections lead to activation of the immune system, causing inflammation and weakening the anchorage. They threaten the integrity of the artificial knee joint throughout the patient’s life. Bacteria can enter the bloodstream via mucous membranes or wounds in the skin, as well as through lung or bladder infections. These bacteria can then settle in the artificial knee joint, where they multiply and cause infection. What makes this so insidious is that it is often a long time before such an infection becomes apparent. Eventual symptoms include severe pain and swelling.

Allergies

Over the course of life, patients can develop an allergy to the prosthesis. The immune system defends itself against the foreign object, which is made from stainless steel (nickel, chromium, cobalt and molybdenum), or to the cement used to adhere it to the bone. This leads to a non-infectious inflammation of the artificial joint, which causes the joint to loosen.

Where any new exertion- or movement-induced pain occurs in the artificial knee joint and does not subside after a short time, advice should definitely be sought from an experienced knee specialist.

How long does it take before you can move normally again?

The muscles recover within six weeks of the operation, at which point the joint has adequate support. In normal cases, it is possible to return to work and resume light exercise after three months.

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