Meniscus complaints are the result of injury or wear-related lesions on the inner or outer meniscus. Cracks in the crescent-shaped cartilage discs are one of the most common injuries in the knee. This is closely related to the function of the menisci and the special anatomy of the knee joint. It is a complex construction made of bones, tendons and ligaments. All parts serve to give the joint sufficient stability while being agile.
The menisci take on a special task in this construction. They are primarily there to compensate for the mismatch between the two bony joint partners. The surface of the lower leg bone is almost flat, while the articular surface of the thigh bone is strongly convex and divided into two. Without further support, the two joint partners would have practically no bony guidance and no securing. This is where the menisci come into play.
Inner and outer menisci make up for the disparity. They consist of crescent-shaped or circular cartilage discs that create a flexible, concave articular surface. They are only attached to the bones on the front and back horns. The rest of the part is mobile and is moved by the movements of the thigh bones when flexing and stretching. That is why they are also called "sliding joint pans". This construction enables flexible adaptation to different joint positions and at the same time increases stability in the knee. The force distribution in different situations is more even and shock absorption is optimized. On the other hand, this complicated construction is very susceptible to injuries and wear.
Causes of meniscal complaints
Meniscal complaints always arise on the basis of cracks. These can be caused by injuries or can result from degenerative changes in old age.
The typical meniscus injury is common in sports, workplace accidents, or car accidents, and is caused by a combination of two components. This consists of the interaction of high shear force with simultaneous twisting in the joint. Such overloads occur when the knee is additionally rotated in a bent position by external force and the lower leg is fixed. Triggers can be violent effects, unfavorable movements in sports or falls from a great height.
Meniscus injuries in sports
There is an increased risk of injury in all sports that involve frequent jumps and landings or start-stop stresses. In contact sports, too, there is an increased risk of injury to the menisci due to the effects of the opponent, which are not always predictable and controllable. Footballers and skiers are particularly at risk because the foot and lower leg are fixed by the lawn or the ski. If the thigh is caused to rotate due to unfavorable movements or external influences, the lower leg cannot follow this movement. If the knee is also in a bent position, a force is created that the menisci cannot withstand. A crack then becomes inevitable.
Accidents as the cause of meniscal tears
In principle, the same mechanisms can work in the case of accidents as in sport. However, this is rarely the case because other circumstances play a role at work, at home or in the car. In the event of an accident, forces are usually so great that the maximum resilience of the menisci is exceeded. At work or at home, these can be falls from a great height. In car accidents, it can be the direct application of force to parts of the car interior. Sudden overstretching or lateral overstretching can also damage the menisci.
The menisci are particularly susceptible to wear. This is related to their metabolic regulation. They are only supplied with blood in the peripheral zones. Most of the food is fed by pressure-dependent diffusion. This type of nutrient supply is relatively slow. Your regeneration potential is therefore rather low.
Meniscal degeneration in the workplace
Activities with permanently high pressure in the joint and on the menisci can accelerate the wear process. Such loads typically occur with tilers who do a large part of their work on their knees or in a crouch. Almost the entire body weight puts a strain on the strongly bent knee joint and the menisci. Wear-induced meniscus damage is recognized as an occupational disease in tilers.
Work in which heavy loads are constantly being lifted is similarly problematic for the meniscus. At some point, the total force that arises is too high and leads to wear on the cartilage discs. Fatally, this is especially true when the loads - as taught in back schools - are lifted gently. Previous damage - for example due to a previous injury - intensifies and accelerates this process enormously.
Meniscus wear in the elderly
The degenerative degradation of the meniscal tissue is a normal side effect of aging. It significantly reduces the resilience of the fabric. If it is far advanced, even small overloads can lead to tears in the tissue. This can be an awkward movement, a slight twisting or a small misstep. With the degree of wear, the already poor ability to regenerate decreases more and more. After such an injury, it is usually not possible to completely restore the meniscus.
Similar to the paragraph on unfavorable working conditions, any kind of permanent overload can damage the menisci in the long term. In the first place is overweight. It is a major risk factor for wear-related meniscal damage.
While obesity strains the entire joint surface and the entire meniscus, misaligned axes have a local negative effect in certain areas. With X-legs, the force in the joint is no longer transmitted axially. Pressure peaks occur in the outer joint area, which promote wear in the outer meniscus. The reverse is true for bow legs. The inside of the joint surface is subjected to more stress and the inner meniscus degenerates faster.
Previous injuries to the meniscus change the mechanical conditions. The friction during movements under load increases. A vicious circle can arise, which leads to another crack, which forms another mechanical obstacle after healing. As a result of such processes, the degeneration can be significantly accelerated.
A rupture of the anterior cruciate ligament can cause instability in the knee joint if the healing is incomplete, which can have a very unfavorable effect on the menisci. The cruciate ligaments serve to center the two joint partners in the knee joint regardless of the joint position. If this function is lost, the articular surfaces move against each other with every movement. Shear forces develop that permanently damage the menisci. The consequences of a posterior cruciate ligament tear are usually much less.
The consequences of degeneration for other structures
The degeneration has immediate consequences for the meniscus, but can also affect the surrounding structures. Basically, the resilience of the meniscus tissue decreases steadily over time. Cracks can occur, but they develop slowly compared to ruptures caused by injuries. However, wear always goes hand in hand with loss of substance. As a result, the meniscus gradually loses height and defects can gradually develop. This affects the cartilage underneath. He is increasingly exposed to an increased pressure load. This also sets degenerative processes in motion that ultimately result in knee osteoarthritis.
Due to the decrease in height of the menisci and their loss of substance, stability in the knee joint also suffers. The contact area between the end of the thigh and the menisci and the joint distance decrease. At the same time, the ligaments and tendons lose tension. This particularly affects the ligaments and cruciate ligaments. All of these factors lead to constant, uncontrollable movements in the joint, which accelerate the wear of the affected structures.
Types of meniscal tear
As already described, meniscal tears can be differentiated according to the cause. While traumatic lesions arise from acute effects of violent wine, degenerative ones are the result of a slow breakdown process. Further criteria for differentiating between different types of meniscal tear are based on the position and the course of the injury.
In the case of a vertical meniscal tear, the dividing line runs between the flat inner part and the outer, still perfused area. The horizontal crack divides the damaged area into an upper and lower part. The shock absorber function is completely or partially lost. If the meniscus is cut through in the middle so that two halves are formed, one speaks of a radial tear. The shock-absorbing function is completely lost. The wear can then proceed very quickly.
The basket handle tear creates a defect that creates a large gap between the remaining sides. Torn parts can fold down into the joint and block it immediately. This increases the friction on the articular cartilage and increases the risk of arthrosis. When the flap is torn, part of the meniscus is torn out of the overall structure. The crack is often transferred to the joint and is therefore usually immediately painful. Finally, the parrot's beak tear is characterized by a deep incision on the inside of the meniscus. Depending on the version, it also affects the shock absorber function.
In the case of acute meniscal injuries, severe symptoms usually develop immediately. Shots of pain are typical, which persist and do not subside even when at rest. When walking, when the pressure in the joint increases and when turning, it increases. However, the pain cannot come from the meniscus itself because it has no pain receptors. Rather, they are caused by surrounding structures that are practically always affected by a meniscus injury. This can be the side ligaments, the cruciate ligaments or bone parts. He often starts with the small straps that fix the meniscus in the area of the front and back horns on the bone.
Often, meniscal tears do not occur in isolation, but in combination with injuries to other structures. The "Unhappy Triad", the "unfortunate triad" that is common among athletes, is particularly notorious. In addition to a tear in the inner meniscus, the ruptures of the inner and anterior cruciate ligaments also belong to this clinical picture. The consequences are extremely serious and require a long period of rehabilitation after the operation.
Pain localization with an isolated meniscal tear depends on where the lesion is located. If the inner meniscus is damaged, the pain manifests itself on the inside of the joint space. It can be reinforced by manual pressure. A crack in the outer meniscus accordingly causes pain in the outer area of the joint space. They also increase with manual pressure. Certain movements exacerbate pain and can provide clues as to which of the two menisci is affected. If it occurs during internal rotation, crouching or when the leg is stretched, the outer meniscus is affected. Conversely, pain aggravation due to external rotation, flexion and straightening from a crouch indicates a lesion of the inner meniscus.
Injury to the meniscus and torn parts irritate the inner skin of the joint capsule. In response, it produces more synovial fluid that is palpable and testable. The fluid accumulation is called joint effusion. It can cause additional pain and limit mobility. Torn or freely moving meniscus parts can get caught in certain movements and cause a blockage of the joint. This can only affect the flexion or only the extension or both directions of movement. A common phenomenon that occurs with meniscal tears is clicking or clicking noises when moving. They arise when torn parts hinder the smooth sliding of the joint partners.
With meniscal lesions that arise as a result of a degenerative process, the course of symptoms is completely different. They often go unnoticed for a long time. Then they appear during periods of stress and manifest themselves in the form of pain and swelling of the knees. The location of the symptoms and the dependence on certain movements is the same as for acute injuries. First of all, the pain subsides again during periods of rest. However, this changes over time and it continues even after the load has ended. In the final stage, it also manifests itself in peace. In addition, movement restrictions in both extension and flexion develop in the course of the disease. All processes can significantly impair mobility.
An experienced doctor can diagnose a meniscal tear with relative certainty already during the clinical examination. Above all, he tests flexibility in flexion and extension and looks at everyday functions, especially the gait pattern. In addition, certain provocation tests are available to confirm the diagnosis. This enables him to examine the pain with regard to its location and intensity. Rotational movements with pressure on the respective meniscus can confirm the suspicion of a meniscus tear and show which meniscus is affected. Imaging methods are also used in diagnostics.
An x-ray is always taken to rule out accompanying bone injuries and to be able to assess the condition of the entire joint. With the help of MRI (magnetic resonance imaging), the doctor gets an overview of the condition of the injured meniscus and the surrounding structures. He can usually see where the lesion is and what type of tear it is. The diagnosis is completed by knee arthroscopy. This happens as part of the operative care before the actual intervention begins. A miniature camera in the inserted arthroscope sends the doctor precise pictures of the situation on site. If the result is positive, the diagnostic part flows seamlessly into the operative part.
After a fresh meniscal tear, the focus is on acute treatment. The swelling in the knee can be reduced by various measures. Ice applications promote metabolism and the removal of excess synovial fluid. However, ice packs should not remain on the joint for too long, as they can otherwise damage the lymphatic vessels. Good decongestant results can also be achieved with curd wrap or a charcoal overlay. All measures described here also contribute to pain relief. The affected leg should be raised. In addition, anti-inflammatory and pain-relieving drugs are usually necessary and useful in the acute phase.
In the further course of therapy, the doctor and patient must make the decision as to whether the operation will be carried out or not. In older people in particular, the surgical indication must be carefully considered. If there is a good chance of self-healing, conservative treatment methods are used. They consist primarily of targeted physiotherapy. The aim is to restore the knee functions to such an extent that active participation in life is possible again. On the one hand, the knee stabilizing muscles are strengthened. This is initially done under instruction and can then be continued independently by the patient. The second part consists mainly of training perception. Those affected learn how to control the knee axis in a wide variety of life situations.
If conservative therapy is unsuccessful and there is no prospect that the torn meniscus will heal on its own, surgery will be unavoidable. The aim of the procedure is to achieve permanent freedom from pain with full functionality of the knee joint. There are the following clear surgical indications for younger patients:
- persistent pain that does not respond to conservative treatments,
- persistent blockages of movement,
- Flap of the meniscus,
- Damage to the inside of the meniscus
- and complete outline.
The decision is more difficult for older people with degenerative changes. Conservative therapy should definitely take precedence. Depending on the type and extent of the damage, cartilage smoothing and the removal of free articular bodies may be necessary in order to delay the development of osteoarthritis.
Operations on meniscal lesions are usually performed arthroscopically. This procedure is significantly less stressful than an open surgery. It shortens the healing and rehabilitation time and reduces the risk of complications. The procedure always follows the premise that as much meniscal tissue as possible is preserved. This is to prevent arthrosis from developing. Depending on the type, course and severity of the injury, two options are available. In one case the injured tissue can be sutured again, in the other case a part is removed.
After the operation, the affected knee can be fully or partially loaded again relatively quickly, while the amount of movement is limited for a while. A special orthosis ensures compliance with the movement limit. Walking supports are used for partial loads. Targeted physiotherapy is extremely important for the success of the therapy. Full resilience is achieved after three to four weeks in the case of partial resections with no complications, with a meniscus suture it takes six to eight weeks before stressful sports are possible again. (fp)
Author and source information
This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.
Dipl. Geogr. Fabian Peters
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