Blood supply of the outer meniscus
Both menisci have no central part and only sparsely interspersed with blood vessels further out. Therefore, the outer – still best supplied with blood – zone of the outer meniscus is also called “red zone”. The supply of nutrients to the inner meniscus is thus mainly via the joint capsule and the synovial fluid (synovia).
The poor blood supply means that lesions (damage) to the menisci heal only slowly. The further inside the damage is, the worse the healing process is. This is important in the treatment of meniscus tears, as tears in the outer zone can generally be treated with sutures due to the better blood supply.
This is less possible with damage in the inner part of the meniscus, where partial removal of meniscal tissue is more appropriate. Basically, a removal of meniscus tissue should only take place if suturing is not possible. This is explained by the fact that the risk of osteoarthritis of the knee joint is higher the less meniscus tissue remains.
Although meniscal lesions are among the most common injuries to the knee joint, the inner meniscus is almost always affected (often in combination with some of the ligaments of the knee joint). The outer meniscus is only rarely injured due to its anatomical conditions. A small injury in the outer meniscus such as a tear in the outer meniscus is much less common than, for example, a tear in the inner meniscus.
The outer meniscus is crescent-shaped and can move more freely than the inner meniscus in the knee, which means that the outer meniscus can better avoid injuries caused by accidents. Sportsmen and women (e.g. skiers, footballers, handball players) are particularly affected by a torn outer meniscus, as often a quick rotation in the knee joint is sufficient to cause a meniscus injury, sometimes also people with particularly knee-straining jobs (e.g. tilers).
But older people are also more susceptible to external meniscus injuries, as the cartilage substance becomes brittle and cracked in the course of life. A torn outer meniscus causes pulling, stabbing pain in the knee area. Typically, the strongest pain is localized around the outer knee joint gap, but often the exact area of pain cannot be precisely determined.
The outer meniscus itself does not hurt because there are no nerve tracts in it. Temporary blockages may occur in the knee, as the torn outer meniscus often restricts mobility in the knee joint. In addition, there may be problems with normal movements such as stretching the lower leg or squatting down.
The pain is often accompanied by knee joint swelling, which can occur within a few hours after the injury. The intensity and duration of the pain depends on the severity of the tear in the outer meniscus. In older people and top athletes, the tear of the outer meniscus can also be degenerative (due to age/exertion), which is often accompanied by no pain or complaints.
Even small tears in the outer meniscus can lead to consequential damage, so that appropriate therapy should be sought early on. Which type of therapy is chosen for a torn outer meniscus depends on various factors such as age, sporting activity and the extent of the complaints. Small tears in the outer meniscus can be treated by: but in many cases an operation is necessary.
This involves a knee joint endoscopy (arthoscopy) under anaesthetic and the outer meniscus is either partially removed or sutured. An untreated damage to the outer meniscus can lead to inflammation of the synovial membrane or even arthrosis of the knee joint. In order to avoid a rupture of the external meniscus, joint-gentle sports (swimming, cycling) should be preferred. For sports that put a lot of strain on the knee joint, you should warm up well and wear suitable protectors that protect and stabilize the knee. – Exercise therapy