Cartilage smoothing to relieve pain in the knee joint

A common cause of complaints in the knee joint is damaged cartilage. Articular cartilage, together with synovial fluid, is responsible for frictionless movement in joints. If the cartilage is damaged and the cartilage surface is uneven, painful movement restrictions can occur.

Even slightly damaged cartilage can only recover with difficulty, as cartilage itself is not supplied with blood. Continued stress in the joint can eventually lead to the development of osteoarthritis. In order to slow down this process and alleviate the discomfort, there are minimally invasive ways to stimulate the regeneration of the cartilage and remove irregularities in the joint. This is called chondroplasty. In addition to chondroplasty, so-called microfracturing or cartilage cell transplantation are performed, among other things, to improve the regeneration of the cartilage and fill cartilage defects.


What is chondroplasty?

Chondroplasty from chondros (meaning the cartilage) and plastic (meaning restoration) refers to the smoothing of cartilage surfaces in joints. Chondroplasty (cartilage smoothing) is most frequently performed in the knee joint. By smoothing the articular cartilage on the joint surfaces, friction during movement can be reduced and further damage to the cartilage surface can be prevented.


What are the treatment options for cartilage defects in the knee?

If there are prolonged (i.e. chronic) complaints in the knee joint, it is advisable to see an orthopaedist and have it examined. This can already rule out many possible diseases and injuries. In most cases, an X-ray examination and an MRI (magnetic resonance imaging) scan are then carried out to examine the knee joint more closely.

With the MRI examination, the cartilage and the ligaments of the knee joint can be assessed very well without radiation exposure. For example, cartilage damage can be identified in the MRI and classified according to severity. Other concomitant injuries or damage, such as ligament injuries or meniscus damage, can also be detected with the help of the MRI examination. If cartilage damage is the cause of the complaints, there are various possible therapy options:

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Therapy options for cartilage damage


If the joint surface is uneven due to damage in the cartilage (from second-degree cartilage damage), there is increased friction between the joint surfaces and consequently pain in the knee joint. Therefore, it is first important to eliminate the cause of the complaints and to smooth the cartilage surface.

Chondroplasty is a minimally invasive arthroscopic procedure (knee arthroscopy). Tools (e.g. a so-called shaver) and a camera are inserted into the knee joint through small incisions. The uneven cartilage surfaces are then smoothed with the help of the shaver or protruding cartilage parts are removed with the help of thermal tools (coblation). Pieces of cartilage floating freely in the synovial fluid or free joint bodies can also be removed during such an arthroscopy (arthroscopy).

Afterwards, the friction and the pain associated with friction should be reduced. However, existing damage to the cartilage surface is not repaired by cartilage smoothing. Further therapies, such as microfracturing or cartilage cell transplantation, are necessary for this.


Microfracturing also takes place during an arthroscopic minimally invasive operation. Through the same small incisions as in chondroplasty, small instruments can be inserted into the knee joint, which cause small fractures in the bone surface below the cartilage damage at points selected by the surgeon. The fracturing causes very small local bleedings.

The stem cells and growth factors in the blood stimulate the overlying cartilage to regenerate. So-called fibrocartilage then forms. Although this is not as resilient as the hyaline joint cartilage, it can initially replenish the existing cartilage damage.

Not all types of cartilage damage are suitable for microfracture. The cartilage defect should not be larger than 4 cm2 and the marginal cartilage should be intact. Defects in the femoral condyle (trochlea) are particularly suitable for microfracture.

In the case of unstable conditions in the knee joint or severe leg axis malpositions (e.g. in the case of a tear of the anterior or posterior cruciate ligament or severe bow or knock knees), microfracturing should not be performed.

Cartilage cell transplantation

In cartilage cell transplantation, a small amount of cartilage is first removed from an unstressed area of the knee joint surface, also in a minimally invasive arthroscopic operation. These cartilage cells are then sent to a laboratory where the cells are first isolated and then multiplied. After about 4 weeks, the autologous cartilage cells obtained can be fixed to a so-called carrier membrane. In a second operation, this can be inserted into the defect zone with the help of a small opening of the joint in order to grow firmly there.

Cartilage cell transplantation is only considered for cartilage damage of 2-3 cm2 or more. In the case of very extensive and advanced cartilage damage, advanced arthrosis or inflammatory diseases of the knee joint, cartilage cell transplantation should be avoided.

Opportunities & Risks

What are the chances and risks of the different treatment methods?

Chondroplasty is generally a very low-risk procedure for smoothing cartilage damage. The chance that the complaints will be reduced by smoothing the cartilage is high. However, one of the two procedures described above is needed to refill the cartilage damage and thus smooth out unevenness in the surfaces of the knee joint. However, these procedures are also rather low-risk. In the second procedure of cartilage cell transplantation, the knee joint is opened with a small incision (arthrotomy), and an arthroscopic procedure is not used as in the other procedures.

Despite all the precautions and experience of the surgeon, complications can occur during the operation. Injuries to the knee joint surface or other structures (e.g. nerves, tendons or ligaments), bleeding into the joint, as well as infections of the joint can be possible complications of the operation. However, the probability of these complications occurring is rather low due to the mostly minimally invasive (i.e. performed with the least possible injury) surgical techniques.

In order to maintain the function of the knee joint in the long term, or to prevent arthritis and further cartilage damage, regular training and the avoidance of overloading are important components of the therapy in addition to the above-mentioned interventions.

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Preparation & Follow-up

What should be considered before and after chondroplasty treatment?

Arthroscopic cartilage smoothing (chondroplasty) is usually a minor procedure that can be performed on an outpatient basis. If microfracture is planned as part of the chondroplasty, this procedure can also be performed in an outpatient setting. Only in the case of a cartilage cell transplantation is the second procedure associated with a short stay in hospital (1-2 nights) for monitoring.

In case of outpatient surgery, you can be picked up from the hospital by an accompanying person on the day of the surgery. It should be ensured that this person can also monitor you for the next 24 hours. You should not drive or doany sports for 24 hours after the operation (if it was performed under general anaesthesia).

Before the operation:

Before all operations, the surgeon will have an informative talk with you about the procedure of the operation and the possible risks mentioned above. In addition, the anaesthetist (anaesthetist) will talk to you about the execution and types of anaesthesia, as well as their side effects. Arthroscopic operations on the knee joint can also be performed without a general anaesthetic, if desired.

On the day of the operation itself, you are not allowed to take anything except a glass of water. It is very important that you remain fasting on this day to avoid certain complications with the anaesthetic.

After the operation:

After the operation, you will be given painkillers (e.g. diclofenac or ibuprofen) in the recovery room to prevent the pain that can occur during such an operation. These substances also inhibit the local inflammatory reaction and swelling, and thus contribute to an improved regeneration of the knee joint. Immediately after the operation, the knee should first be cooled and rested.

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