The meniscus is the wedge of white fibrous cartilage sandwiched between the two large bones of the knee joint, the femur (thighbone) and the tibia (shinbone, like a spacer). It functions as a shock absorber and also allows some rotation of the knee. In a word it is one of those body parts you don't know you don't know you've got until you damage it!
Tears of the meniscus are very often the result of a twisting injury, as might occur when a football player lands on one leg from a jump while his body is still twisting. This 'torque'can cause the fibres of the meniscus to be disrupted and a split can occur, rendering the knee bio-mechanically unsound, and leading to intermittent pain, clicking and locking-up of the joint.
Now the issue with these tears relates to their blood supply and healing. Each knee has two meniscus (or menisci), one on the inner aspect and one on the outer aspect. They are shaped like a flattened half- moon, wedged between the bones.
A now classic set of studies by Steve Arnocsky demonstrated that the meniscus is supplied by a network of tiny blood vessels around the fatter outer rim (the 'red' zone), while the thin inner rim (the white zone) has virtually no blood supply at all, taking its nourishment like a parasite from the joint fluid which bathes the knee joint.
A tear in the red zone has a good chance of healing by itself. If the torn bit is sewn up (sutured) then there is a very good chance of healing, particularly if the tear is still fresh.
A tear in the white zone, in contrast, is unlikely to heal, and there is little additional harm done in removing the torn bit during surgery.
Tears tend to render the knee bio-mechanically unstable and an unhealed tear gets subjected to repeated stress and can propagate, sometimes forming a long loose bit (a 'bucket handle' or flap) which can catch in the joint and lock it, causing damage to the joint surfaces ('arthritis').
The rim of the meniscus takes the main brunt of shock absorption, and excising the whole meniscus is almost certainly committing the patient to knee arthritis in later years. It needs to be pointed out that in early years of knee surgery this would have been common practice, but nowadays the leading surgeon would recommend that the meniscus rim be maintained at all cost.
A number of issues are of interest patients:
A publication in the professional medical journal, 'The Knee' (vol 9, 2002, pp 181-187) relates to a thirteen year follow- up study by three Belgian doctors from Ghant University Hospital.
They followed a group for thirteen years after they had similar meniscal suture operations under keyhole surgery (arthroscopy). All were examined before and after surgery and at the end of the study period, and all had the MRI examinations. Standard tests and scoring systems were used to compare their outcome.
In their small sample of patients, the authors of the thirteen year study found that:
The authors state emphatically that the surgeon needs to select the patients well, and not try to suture degenerative poor- quality meniscal tissue.
They advocate also that the sutures be multiple, especially in longer tears, where they should be placed less than 4mm apart.
We are likely to see more studies such as this, with 10-20 years follow- up, and the picture will become clearer.
But many surgeons are still removing menisci which could be sutured, and it will be interesting to review in 10 years time the number of legal cases related to such current practice as our global internet population wakes up.