Function
The meniscus has the function of transmitting the force as a shock absorber from the thigh to the lower leg (shin bone = tibia). Due to its wedge-shaped appearance, the meniscus fills the gap between the round femoral condyle and the almost straight tibial plateau. The elastic meniscus adapts to movement.
It also has a stabilizing function as a “lateral limiter”. The meniscus improves the distribution of the joint fluid. The meniscus is very poorly supplied with blood!
- Red zone: close to the capsule = good blood circulation
- Red-white zone: limited blood circulation
- White zone: no blood circulation
Diseases
The most common disease of the meniscus is meniscus tear meniscus damage. Since the meniscus is only supplied with blood in its peripheral zones, it has only a limited regeneration potential. In old age, meniscal wear (meniscal degeneration) is normal.
Further information about the treatment of damaged menisci can be found here:
- Meniscus treatment
Injuries to the meniscus are among the most common knee injuries and are often the result of a sports accident. A typical injury mechanism can be, for example, an unfortunate fall during a skiing vacation: Those affected lose control on the piste, a ski gets stuck in deep snow, while the knee joint is twisted by the force of the fall. Thus massive shear forces affect the meniscus – finally it overstretches and tears!
Older patients can also suffer a wear-related (degenerative) meniscus tear without any previous trauma. Preferably the inner meniscus is affected, since it is firmly attached to the inner ligament of the knee and therefore has less room to move during rotational movements. Combined ligament injuries are more common than isolated damage to the meniscus.
For example, the anterior cruciate ligament, the inner knee ligament and the inner meniscus can tear at the same time! One speaks then of an “Unhappy Triad”. Characteristically, an acute meniscus tear is accompanied by three symptoms (“symptom triad”): 1) Pain Patients report strong, immediately shooting pain in the affected knee joint.
Both stress and pressure are very painful. 2.) Blocking The knee joint can be mechanically blocked by e.g. incarceration of the torn off meniscus ends.
Affected persons describe a kind of “snapping” over the joint. This results in knee stiffness, especially when stretching is attempted. 3.)
Swelling If the base of the meniscus is torn and is well supplied with blood, a large hematoma (“bruise“) develops within a few minutes, accompanied by severe swelling.The next day at the latest, a joint effusion is also observed. In order to confirm the diagnosis of meniscus rupture, the attending physician carries out specific pain provocation and pain examinations. These include, for example, the Steinmann I sign: The patient bends his knee at a 90 degree angle while the examiner turns the knee jerkily outwards.
If pain occurs in the area of the inner joint space, this is to be interpreted as an indication of an inner meniscus injury. In addition to manual examinations, however, an imaging procedure must be used if there is a strong suspicion. In principle, X-rays are suitable for this purpose, but in most cases, fresh injuries are not visible.
Today, MRI (magnetic resonance imaging) is the gold standard for diagnostic confirmation. Without radiation exposure, high-resolution images can provide clarity. Depending on the problem, the administration of a contrast medium may be necessary.
Experienced examiners can even visualize the injury with a suitable ultrasound machine. Therapeutically, a conservative (non-surgical) option is offered in very rare cases, in addition to surgical therapy. This includes treatment with anti-inflammatory tablets and ointments, injections of local anaesthetics or physiotherapy.
Today, the standard therapy for meniscus tears is arthroscopic treatment. Using minimally invasive techniques (“keyhole principle”), a tiny camera and surgical instruments are inserted into the knee joint. Advantages are a lower complication rate, shorter healing phase, and significantly smaller operation scars (about 5-10 mm).
Open meniscus operations are now only performed in individual cases and in cases of severe concomitant damage, e.g. bone fractures or massive further ligament injuries. If possible, the meniscus should always be preserved! Nevertheless, the applied procedure always depends on the severity of injury, possible concomitant damage and individual overall constitution.
In the best case, the torn off ends can simply be sutured again (meniscus refixation). This method is especially aimed at young and active patients, without wear-related cartilage changes. However, there is no real upper age limit.
A great advantage can be the possible complete functional restoration of the knee joint. In the ideal case, affected patients can thus regain their complete, athletic performance capability! In individual cases, however, the longer rehabilitation phase required can be regarded as problematic.
In the case of meniscus refixation, an approximately six-month sports break must be observed. This also applies to knee-straining activities in the context of professional life, e.g. tiling or gardening. Therefore some patients decide to have a partial removal of the meniscus (partial meniscectomy), despite the theoretically possible refixation.
In this procedure, the physician removes the damaged, non-recoverable meniscal tissue. This is usually followed by joint irrigation, so that any remaining fragments can also be removed. In the foreground, is a desired freedom from symptoms, especially pain.
Despite the most modern arthroscopic technique, not every meniscus can be preserved. However, total removal (meniscusectomy) carries many risks, such as knee joint arthrosis, and should be used very cautiously. For this reason, meniscus transplantation procedures have been increasingly developed in recent years.
However, long-term success is not yet 100% guaranteed, so it remains to be seen what possibilities will open up. The most frequent complication of arthroscopy is an injury to the saphenous nerve. It is a purely sensitive nerve and supplies the skin of the inner side of the lower leg.
As a result of pressure damage or knotting during arthroscopy, patients experience discomfort (tingling, numbness, etc.) in the affected area. However, in most cases these symptoms disappear after a few months without external intervention!
Unfortunately, the “rerupture rate”, i.e. the rate of a new meniscus tear after surgery, is still about 25%! Especially affected are patients in whom a restoration of the anterior cruciate ligament has taken place at the same time. A further late consequence is the increased tendency to develop knee joint arthrosis, i.e. age-related wear and tear of the cartilage surface.
In principle, the more meniscus had to be removed, the higher the risk of developing arthrosis. But why is this so?Our menisci have a kind of “shock absorbing effect” within the knee joint. If they are absent or only partially present, the weight and load is distributed unevenly in the joint.
As a result, remaining cartilage components are overstressed, resulting in arthrosis. After the arthroscopy, the follow-up treatment follows. Depending on the extent of the operation, the knee joint must either be immobilized for some time (e.g. with crutches) or physiotherapy can be started immediately.
