Blood supply
Both menisci (inner meniscus and outer meniscus) are in their central part not at all and further outside only sparsely interspersed with blood vessels. Therefore, the outer – still best supplied with blood – zone also has the name “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, since 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.
Clinical significance
Meniscus lesions are among the most common injuries to the knee joint. The inner meniscus is – due to its adhesion to the medial collateral ligament – much more frequently affected by injuries than the outer meniscus. Typically, it tears during rotational movements when the knee is bent and the foot is fixed to the ground and therefore does not rotate. For example, when skiing or playing soccer with cleated shoes. Frequently, it is not alone affected, but ruptures within the scope of the so-called “unhappy triad” (unhappy triad), with an additional rupture of the medial collateral ligament and the anterior cruciate ligament (ligamentum cruciatus anterius).
Torn or damaged inner meniscus
The inner meniscus is most frequently damaged in sports injuries. Especially movements in the knee joint with abrupt stops, rotational movements or dislocations can cause damage to the menisci. Sports in which such movements occur particularly frequently include soccer, basketball, tennis and skiing.
The most common non-traumatic cause of inner meniscus damage is wear-related meniscus injuries.Wear and tear of the joint surfaces over the years or with constant incorrect loading leads to abrasion of the menisci. On the one hand, this causes damage to the menisci themselves, but on the other hand they become more susceptible to traumatic injuries. A person with a worn meniscus will develop a meniscus tear more quickly under physical stress than a person with intact menisci.
Incorrect strains that damage the menisci include congenital leg malpositions (knock-knees or bow legs), as well as frequent squatting or overweight work. In a degenerative process on the inner meniscus, the affected person usually feels increasing pain when the knee is under stress. The extent of the pain varies depending on the severity of the injury.
If the meniscus is only slightly torn, the pain may be only mild. If the meniscus is torn, the knee often cannot be moved in the normal range of motion. If parts of the meniscus have already rubbed or lifted off, knee flexion or extension can cause cracking noises in the knee joint.
If a meniscus suddenly tears in the course of an accident, this usually manifests itself as strong, stabbing pain shooting into the knee, which makes further strain on the knee impossible. In addition, a joint effusion often develops, which leads to a swelling of the knee. A normal range of motion is then no longer given.
Also, blasted off cartilage parts can lead to an acute blockage of the joint, which can then no longer or hardly be bent or stretched at all. The most important medical instrument for the diagnosis of an inner meniscus tear is the physical examination. Through various orthopedic tests, the doctor can check the involvement of the menisci.
Different hand movements, pressure points and sequences of movements are used and these are checked for painfulness. If the inner meniscus is damaged, the pain is concentrated on the inside of the knee joint gap. In imaging, magnetic resonance imaging (MRI of the knee) is particularly suitable for detecting a torn meniscus.
Arthroscopy can also be used to determine the extent of damage to the meniscus. This can be important for the therapeutic procedure to be chosen. The therapy of the meniscus tear is important, since otherwise long-term complications can arise.
Especially if parts of the inner meniscus have already entered the joint space, a surgical treatment of the injury should be chosen, because the free cartilage piece leads to further damage of the joint surfaces due to friction. In the long run, this in turn leads to the development of arthrosis in the knee joint. Depending on the location of the tear, meniscal suturing is to be preferred.
However, this can only be performed in places where the inner meniscus is better supplied with blood. Otherwise, the suture will not be able to lead to a fusion of the meniscus parts. As alternative procedures, partial meniscus resection or complete meniscus resection can be considered in such areas with poor blood supply.
With partial meniscectomy, as little meniscal tissue as possible is removed. Particularly free fragments are removed from the joint space so that they do not lead to further damage to the joint surfaces. If the meniscus tear is very large, sometimes the whole meniscus has to be removed to achieve an optimal therapy result.
Subsequently, the removed inner meniscus must be replaced by a transplant or an artificial meniscus. Physiotherapeutic exercises to restore the mobility of the joint are particularly important. Depending on the extent of the injury, it can take weeks to months before the knee can be loaded normally again and sport can be practiced again.
The treating physician must discuss this individually with the patient. Minor meniscus injuries do not necessarily require surgery. In this case, often the relief of the affected leg with an immobilization of the knee for a few weeks, the intake of painkillers and physiotherapy help to achieve a good healing.
An injury to the inner meniscus can be very painful. Meniscus tears that occur suddenly, for example as a result of an accident or a sports injury, usually result in shooting pain in the affected knee joint. If a piece of cartilage becomes completely detached or protrudes into the joint space, this can lead to an abrupt blockage of the knee joint mobility.The pain caused by a degenerative process at the menisci is rather diffuse and less shooting.
They manifest themselves mainly in stressful situations and increase with the extent of the strain. Damage to the inner meniscus is particularly indicated by pain in the area of the joint gap, which can also be triggered by pressure with the fingers, or pain when the knee is turned outwards (external rotation), as well as pain when squatting down or standing up from a squatting position. In addition, a joint effusion can develop as part of a meniscus injury.
In this case, fluid accumulates in the joint space and presses on the surrounding structures. Depending on the extent of the effusion, it can also cause pain, as the knee is then very tight and taut. If a torn meniscus is not treated appropriately, arthrosis in the knee joint can develop in the long term.
This too is then characterized by painfulness when the knee is moved. In order to prevent this, an early and individually adapted therapy is indispensable. Surgery is not always necessary.
