Cartilage is a medical term which refers to fibrous or bony tissue which lies within or on the surface of joints. The major joints of the body such as the knee joint contain a specific type of cartilage known as hyaline cartilage. The hyaline cartilage covers the ends of the thigh bone (femur) and lower leg bone (tibia) and essentially provides the joint surfaces to the knee joint.
Healthy hyaline cartilage is absolutely essential to the correct functioning of joints and for the prevention of developing more rapid age related changes (osteoarthritis) to joints. The reason for this is that hyaline cartilage combines a unique shock absorbing ability with an extremely friction free surface. To date we are unable to engineer a material which has the friction free properties of hyaline cartilage! Together, these properties significantly reduce the forces within the knee joint during everyday tasks and sports.
Given this key function of hyaline cartilage early and optimal surgical care in managing any cartilage damage or cartilage defect is vital. In the event of injury, two forms of surgery are available.
Specialist orthopaedic knee surgeons can either perform an operative technique known as microfracture to the area of cartilage damage or cartilage defect. Alternatively, with new operative techniques a hyaline cartilage transplant is possible.
The type of surgery offered may depend on several factors including:
- The general health of the knee
- The type and extent of the cartilage damage or cartilage defect
- The activity level of the patient
- The age of the patient
Age related processes, especially to weight bearing joints such as the knees is entirely normal. This process, known as osteoarthritis is distinct from an isolated area of hyaline cartilage damage or a hyaline cartilage defect.
Cartilage damage or a cartilage defect can arise from an unknown cause, often during teenage development or can be as a result of a significant knee injury. Knee cartilage surgery is aimed at this type of cartilage damage and cartilage defects.
Before the surgical procedure itself commences your surgical team will position appropriate equipment to monitor vital signs. These will include a blood pressure cuff to monitor blood pressure, ECG leads to monitor the electrical activity of the heart and a monitor to measure oxygen levels.
A hyaline cartilage microfracture procedure or a cartilage implantation procedure are both carried out using keyhole surgery (arthroscopy).
This involves making very small incisions on either side of the knee and inserting a small tube known as an endoscope into the knee joint. Throughout an arthroscopic knee procedure fluid is pressurised into the joint which aids visualisation of certain parts of the knee joint and also reduces any chances of infection.
Via special instrumentation on the end of the endoscope the surgeon is able to visualise the knee joint and if the chosen operation is microfracture drill in to the bone beneath the area of cartilage damage. This stimulates bleeding and over the subsequent weeks stimulates the area to form a fibrous cartilage to help reduce pain.
If a hyaline cartilage implantation procedure is being considered this will be done over two stages. The first stage is an arthroscopy to better assess the area of cartilage damage or cartilage defect.
During this operation the surgeon will harvest a small piece of cartilage from the knee. This harvested hyaline cartilage will then be grown in lab conditions and the second operation, a number of weeks later will be undertaken to carefully mould and stitch the harvested cartilage over the area of cartilage damage or cartilage defect.
General complications which can occur with any type of invasive surgery can occur in a small number of patients who undergo a cartilage surgery. These can include:
- Reaction to undergoing a general anaesthetic can be highly variable among individuals. Drowsiness is common and some individuals may experience some nausea and vomiting following surgery.
- A blood clot (deep vein thrombosis - DVT) can occur after any type of surgery due to the reduced time spent being active (activity normally helps to pump the blood around the legs). Our physiotherapists will encourage bed and chair exercises to help keep the blood moving in the lower legs.
- In rare cases if a blood clot develops it can travel to the lungs which is known as a pulmonary embolism (PE) or travel to the brain which can be life threatening or cause permanent neurological damage.
- The medication/s used as part of the general anaesthetic reduce the sensation of the nerves and muscles around the bladder which can lead to urinary retention. In a small number of cases individuals may need catheterization for a short period after their surgery until they are able to pass urine properly.
- Due to general activity being reduced following surgery as well as the effects of some general anaesthesia and pain controlling medication individuals will tend to breath in a shallower pattern. For this reason, patients are encouraged to complete regular breathing exercises to circulate the air in the lungs and prevent chest infections following cartilage surgery.
There is also some specific information to be aware of if undergoing knee cartilage surgery:
- In some cases knee pain and/ or instability can remain even after a successful operation.
- The new section of knee cartilage can sometimes fail to adequately integrate itself to the surrounding tissues leading to ongoing knee instability.
- Due to the above issues some active sportsmen/ women are still unable to get back to high level sporting activity involving impact work and twisting/ turning.
Following your surgery you will be returned to your room and monitored by members of our nursing staff. Immediately after surgery, you will have a tight bandage on the knee which will limit the movement available to your knee. Prior to initially weight bearing our specialist physiotherapists will visit you and supervise your transfer out of bed in to sitting and standing as well as supervise you walking for the first time.
Following a microfracture procedure for knee cartilage damage or cartilage defect there will often be no formal weight bearing restrictions. Your specialist will be happy for you to progress under the supervision of the physiotherapy team as your pain and strength allow.
However, if a cartilage implantation procedure has been undertaken there will be a significant period of weight bearing restriction and time in a brace to aid the stability of the knee and limit movement following the surgery.
The exact time frame for these limitations will be determined by the exact nature of the surgery undertaken and your surgeon’s assessment of how well the transplanted graft has been stabilised to replace the damaged area.
You will be reviewed by your surgeon until they are entirely happy with lifting the restrictions and thereafter our expert physiotherapy team will tailor your rehabilitation and advise you how to progress your flexibility and strengthening exercises appropriately.
Progressions of the strengthening exercises will normally involve some light exercising on a static cycle in the gym and progressing exercises to those involving weight bearing. These exercises, known as compound exercises more quickly achieve strength in the operated knee to enable you to walk, sit to stand and climb stairs more effectively. Some examples of these exercises are listed below:
- Sit to stand repeats
- Wall squats
- Low step up
Depending on your specific goals around your occupation or return to sports, our physiotherapists will advise you on further specific rehabilitation and fitness drills to enable you to safely achieve your goals.