Let’s explain what the meniscus and the cartilage are, what the difference between them is and what treatments are available to treat the injuries that occur to them.
Meniscus: this is a crescent shaped fibrocartilage that is between the bones in the knee joint. It acts as a shock absorber. We are taking weight through the meniscus on every step we take. It is therefore no surprise that theses structures can wear and eventually tear even through normal life.
There are actually 2 in the knee. If worn or torn they cause pain on the side of the knee where the problem is along the line of the joint. The pain is worse when twisting or bending. Sometimes there is a build up of fluid in the knee.
They can also be torn in a sudden twisting injury or on bending down. Then they can actually get stuck in the joint causing locking.
About ½ of people with an anterior cruciate ligament tear also have a tear of a meniscus.
The diagnosis can be made by a proper history and examination. An MRI can be useful in a small number of cases if there is any doubt after the examination. In fact the MRI is most useful when the patient has little trouble and needs the reassurance of a normal scan to get them back to full activity.
A tear can only be treated by an arthroscopy. At the arthroscopy the tear is usually trimmed back with power tools and electrosurgery devices. In a small number of cases there is a smooth tear that will hold a stitch well. In this situation the tear can be repaired with special stitches that are placed inside the knee while it is viewed on the monitor without the need for open surgery (keyhole surgery). This happens most commonly in the younger patient with a sudden injury.
When a tear is trimmed back the patient can usually return to full activities after 4 weeks.
When a tear is repaired with stitches it will take at least 3 months before the patient can go back to sport.
Cartilage: there is confusion when talking about cartilage injuries. The meniscus is also called cartilage but it is the covering cartilage of the bones that we are talking about here. The ends of the bones in the knee are covered by hyaline cartilage. This varies from about 3 to 5 millimetres in depth. Again we are walking and running taking weight through the cartilage every day. It can wear. This starts as a softening, then fissuring and then the cartilage starts to break up. It can start to come away from the bone and leave it exposed.
I am not sure that increased levels of activity cause this wear as it can be seen in sports people and in people who do very little. It can also be seen in any age group.
Cartilage wear can lead to swelling and pain in the knee. However it does not affect everyone in the same way. Some have a lot more trouble than others with similar levels of wear.
Cartilage wear is diagnosed by a history and examination. An x-ray is the best investigation as this will give the best indication as to whether the patient needs a knee replacement or not. Obviously there is no point in having arthroscopic surgery (keyhole surgery) if you need a knee replacement. I find that MRI is very poor at demonstrating early cartilage wear and I feel that it is not needed as a routine investigation.
In the early stages it can be treated with rest and physiotherapy. If not settling an arthroscopy can make a great difference. Loose cartilage and cartilage about to fall away from the bone is removed with the arthroscopic shaver. The edges of the damaged cartilage can then be treated with an electrosurgery ablator which seals it.
Sometimes some small holes can be placed in the underlying bone to release the bone marrow with its stem cells. These cells have the ability to grow a scar like cartilage over the defect. This is called the microfracture technique.
This treatment can slow down the progression of the wear and relieve pain and swelling. However not surprisingly not all knees are sorted out and wear can continue. Patients who continue to have a lot of trouble may need a knee replacement.
Return to full sports is more uncertain after cartilage injury. It usually takes 3 months and it is very advisable to have the muscles in peak condition as this will protect the knee. Some people may decrease their activity level because they are just not able to do what they did before because of swelling and discomfort in the knee.
At the present time techniques to replace and regenerate hyaline cartilage are been used on an experimental basis and they have not yet been clearly shown to definitely benefit the patient. It is likely however that sometime in the next 5 years a good, safe, beneficial technique will emerge from the research.