Knee replacementsKnee replacements

Brief information
Surgical term:
knee replacement, TKR (total knee replacement), bicondylar resurfacing, sliding prosthesis

When is a surgery indicated?
If wear and tear of the knee joint occurs that can no longer be treated conservatively, causes severe pain on exercise and at rest and markedly restricts the patient's everyday activities, the damaged part or parts of the knee joint can be replaced surgically with a prosthesis in order to reduce pain and improve the function of the joint.


Surgery technique:
Under full or partial anaesthesia, the knee joint is exposed and the damaged articular surface removed. Depending on the extent of the damage, the entire joint surface or only the more badly affected parts are replaced with a metal plate that is adapted to the natural shape of the joint. The prosthesis can then be secured in place with or without bone cement. Sometimes, to relieve pain, the back of the patella (kneecap) also needs to be replaced. There are various types of specialist prosthesis available for more difficult cases.

Inpatient stay:
patients are required to stay in hospital for around 8 - 10 days.

Follow-up treatment:
Immediately after the surgery, movement exercises are commenced with walking aids. Normally, a period of convalescence and recovery in a specialist facility follows the inpatient stay.
By the 5th or 6th week, complete and independent weight-bearing should be possible.

In-depth information

The knee joint is the largest joint in the human body. Its function is crucial for upright walking. Over the years, the cartilage around the joint gets naturally worn and can progress to a stage at which severe pain occurs on exertion and there is considerable limitation of the joint's mobility. This is generally known as knee arthrosis or gonarthrosis.
In general, there is severe extensive wear and tear of the joint surfaces. First affected are the cartilage and menisci, then the layer of bone itself.
This frictional wear causes inflammatory reactions and gliding disturbances in the joint, leading to pain on exertion and sometimes even at rest.
The reasons behind this wear and tear process are partly due to the general ageing process or adverse mechanical stresses on the joint. These latter are primarily caused by excess weight strain (being overweight), misalignment of the axes of the legs (bow legs or knock-knees), or long-term unequal load distribution caused by extreme physical work.
Accidents and the consequences of these, such as cruciate ligament tear with subsequent instability, or a bone fracture close to the knee, can also encourage the development of arthrosis.

When is a knee replacement indicated?
If there is knee joint arthrosis that cannot be improved with joint-preserving surgical or non-surgical measures, and if the pain of the condition is impairing the patient's mobility, replacing the worn parts of the joint can often produce freedom from pain and therefore restore the patient's mobility.

How is the operation performed?
The surgery is performed under partial or full anaesthesia. Through an incision on the anterior surface of the knee, the knee joint is exposed and the diseased parts of the articular surface are removed using special instruments. Using special templates, the femur and tibia are then prepared in sequence and trial prostheses are inserted to check the anticipated result. Only then are the final prosthesis components inserted.
A plastic layer (of polyethylene) is inserted as a buffer and sliding surface between the main components of the prosthesis.
The parts of the prosthesis itself are made from special, very high-quality metal alloys. With cement-free prostheses, the parts that contact the bone are made from titanium.

A distinction is currently made between three different types of knee joint replacement.
With the "sliding prosthesis", either the interior or exterior half of the knee joint is replaced. For this to happen, the remainder of the joint must have intact cartilage and an intact capsular ligament apparatus, i.e. be functioning normally, since these structures are not affected by this operation.
With surface replacement prosthesis, the entire surface of the knee joint is "crowned". For this surgery to be possible, the body's own ligaments must have adequate stability. If there are additional problems that can be caused by the posterior surface of the patella, this may also be replaced.

Both of these types of prosthesis can, in principle, be inserted with or without bone cement.
An axially supported knee endoprosthesis is used in cases of advanced joint arthrosis with additional marked misalignment of the axis of the knee and / or joint instability. Unlike with the types of prosthesis listed above, the parts of the prosthesis in this case are linked to each other but can still move, and the prosthesis is also anchored into the femur and tibia using stems. This coupling mechanism achieves additional stabilisation of the joint.

How long will I have to stay in hospital for?
The inpatient stay after the surgery is around 8-10 days. The pre-operative checks can normally be carried out as an outpatient.

What follow-up treatment will I require?
On the very first day after the surgery, physiotherapy exercises are started. Passive movements on mobile rails and active strengthening exercises are combined to suit each individual. In addition to this, patients are helped to walk again with crutches and later helped to climb stairs.
Following inpatient treatment there is generally a period of rehabilitation which may be organised as an outpatient or at an inpatient facility, depending on the patient's needs and their agreement with their health insurance provider.