Articular cartilage in the knee is the smooth membrane which covers the ends of the bones and forms the bearing surface. If there is injury to this cartilage due to anaccident or a sports injury, the knee remains persistently painful and swells up recurrently. If the damage to the bearing surface cartilage occurs at a young age this can lead to rapid onset of arthritis in the knee.
The major problem that is faced by knee surgeons is that the articular cartilage of the knee, once damaged, does not grow back. Various techniques have been used to address this problem. The traditional technique is to clear the base of the defect and make multiple holes in the defect. This technique is called microfracture, which can be done by the keyhole method. The multiple holes made in the base of the defect allow a blood clot to form in the defect which gets converted into fibrocartilage, which is not the same as the articular cartilage of the knee but often helps to relieve the pain. As this fibrocartilage does not have the same biomechanical strength as the original cartilage, it can wear away over a period of time leading to recurrence of pain.
Recently a new technique has been developed to treat cartilage defects called autologous chondrocyte transplantation. This technique was developed in Sweden and has been used on a number of patients in the UK and the US. As the long term success of this technique is not yet known, this is still in the research phase and is usually done as part of a clinical trial.
What happens during the knee surgery?
The knee surgery is carried out in two stages. Both operations are carried out under a general anaesthetic. During the first stage a small sample of healthy cartilage is taken from the knee by the keyhole technique. The sample is sent to the laboratory for the cartilage cells to be grown (cellculture) 3-5 weeks following the first operation, the cartilage cells are available on a membrane. During the second stage of the operation the knee is opened and the membrane having the cartilage cells is used to cover the defect of the cartilage.
What happens after the knee surgery?
The first stage of the operation is usually undertaken as a day surgery procedure and hence you can be discharged on the same day as the knee surgery. The second stage of the operation requires a stay in hospital of about 2-3 days until you are walking comfortably with the help of a physiotherapist. You will not be able to put full weight through the operated leg for about six weeks following the knee surgery but will be able to move the knee straight away after the operation.
In the long run you will be followed up on a regular basis to see the effect of the operation. The long term success for this particular procedure is not known as yet but appears to be promising.
What are the risks associated with cartilage repair?
The risks include infection, deep vein thrombosis (a blood clot in the leg vein), numbness on the front of the knee and rarely an allergic reaction to a substance used in cell transplantation.