Where exactly is the meniscus located and what is its function?
The meniscus tissue is elastic and lies like a disc between the femoral condyle and the tibial plateau. There is an inner and outer meniscus. The cartilaginous meniscus tissue is the most important buffer during impact loads on the knee.
The meniscus has many functions. By increasing the surface area, the total load is divided on the knee joint. It is responsible for the arsorbtion, for the synovial fluid and stability of the knee joint. This makes the menisci in the knee joint the most important protection for the articular cartilage.
Fig.1: Anatomical preparation (Siebold and Metz) with inner and outer meniscus.
Whats the material specificity of the meniscus?
The meniscus has a dense fibrous tissue that is supplied with blood only at the edge to the joint capsule. This zone is called the red-red zone. There are no nerve fibers and therefore no pain is initially felt with degeneration or injury. However, a degenerative or acute rupture of the meniscus causes displacement and entrapment of meniscal tissue. Weight bearing changes and irritation of the synovial membrane occurs.
Why does a meniscus tear and can it heal again?
Fresh meniscal tears in young patients usually have a good chance of healing. Of course, healing depends on the shape of the tear. Every tissue is subject to natural aging, including the meniscus tissue. Genetic factors play an important role here. The natural aging process is obviously affected by the degree of stress in everyday life.
What are the differences?
Generally poor blood supply to the meniscus means that only healthy meniscal tissue has a sufficient chance of healing in young patients. Tears close to the capsule as well as a meniscus tear in combination with an ACL injury have particularly good healing prospects. In the case of degenerative changes, however, it becomes difficult because there is no healing and thus no reduction in pain.
Fig.2: Healthy meniscus
Which are the consequences of a meniscus tear for the knee joint?
An acute or degenerative meniscus injury should in any case be clarified by a knee specialist in order to initiate an early individual therapy.
Ruptured meniscus leads to a disturbed sliding surface between the upper and lower leg. It can also entrap loosened parts of the meniscus, causing high stresses between the cartilage of the upper and lower leg and destroying the sensitive cartilage surface.
What happens to the cartilage surface if a ruptured meniscus is not repaired?
The once very smooth surface of the cartilage becomes dull and softened. That’ s the starting point for a gradual defibration and abrasion of the cartilage. We speak of arthrosis when the cartilage has worn down to the surface of the bone. The wear and tear can go unnoticed for a long time until it finally triggers pain.
Fig.3: Examples of impinged meniscus.
Why do especially athletes have problems with the meniscus? In what way does a tear occur?
Sportsmen and women often suffer an acute meniscus tear as a result of excessive stress on the meniscus. Patients usually describe a stabbing pain in the knee. Fresh injuries often lead to an acute functional limitation in sports or to a permanent inability. Due to the complaints, the diagnosis of the meniscus lesion is made at an early stage and surgical therapy is initiated immediately. If the fresh meniscus injury is not treated, mechanical irritation and pinching of the meniscus can cause damage, as well as damage to the articular cartilage with early arthrosis.
What are the symptoms of a meniscus tear?
With degenerative tears of the meniscus, the process develops gradually, so that disorders are only noticed after a while. An accident does not always have to be the cause.Everyday stress, e.g. getting out of the car or going into a deep squat, is enough to suddenly trigger pain from the already degenerative meniscus.
On what do you have to pay attention?
If a flap tear or a basket handle tear occurs, acute painful locking of the knee joint with restriction of the range of motion may occur. In most cases, there is a painful inhibition of extension, which can be temporarily relieved by certain rotational movements with reduction of the meniscus. A snapping of the meniscal flap is also described by the patient. Everyday loads can be performed on meniscal tears, but patients in jobs where they have to stand a lot complain of pain in the area of the inner or outer joint space. Heavier loads result in more pain with irritation and effusion in the knee joint. There is also often local overheating of the knee joint.
Fig.4: Unstable large basket handle tear (left) and blockage due to popped-out basket handle tear (right).
What exactly does the orthopedist examine?
The diagnosis can be made by a specific clinical examination in the area of the inner and outer meniscus. In addition, standardized X-ray images taken while the patient is standing. Also the exclude bony causes of the complaints and to determine the degree of arthrosis. Magnetic resonance imaging (MRI) is certainly the most reliable method to visualize a meniscus tear. From our point of view, an exact diagnosis of the meniscus injury is necessary to initiate the appropriate individual therapy.
Fig.5: Meniscus examination, X-ray (lateral).
Fig.6: MRI images of intact outer meniscus (left), intact inner meniscus (center) and meniscus tear (right).
Is it possible to avoid surgery?
If the patient is free of symptoms, a conservative (non-surgical) therapy can be attempted with physiotherapy and appropriate medication. Especially in older or less active patients, surgery can often be avoided.
When is an endoscopy (arthroscopy) necessary?
In most cases, however, there are persistent complaints in everyday life, which limit the quality of life significantly. It is then recommended to perform a knee arthroscopy. This allows excellent visualization and examination of the articular cartilage and menisci while treating the damage. Basically, it is important to preserve as much functional meniscal tissue as possible in order to reduce the long-term consequences of meniscal surgery. For this reason, preserving the meniscal tissue as much as possible by suturing it is absolutely necessary.
Tear in the meniscus – how to repair it?
We have a variety of different suture techniques and are very familiar with meniscus suturing. Only this allows for optimal fixation of the torn meniscus and creates optimal healing conditions.
Especially in the case of a basket handle tear, preservation of the meniscus is reasonable, since removal of the large basket handle flap would otherwise be equivalent to extensive meniscus removal.
Fig.7: Examples of meniscus suture.
What if the meniscus has to be (completely) removed?
Patients who lose their meniscus in an accident at a young age may develop early arthrosis in the medium term. This is often combined with the early onset of painful cartilage damage of the femoral condyle and the tibial plateau. Pain and bruising in the knee joint are the first signs of the development of arthrosis and an important indication of early overloading of the joint section.
What exactly is a meniscus transplant?
An important surgical procedure in this situation is the transplantation of a donor meniscus. Both the inner and outer meniscus can be replaced. The donor meniscus is ordered from internationally accredited tissue banks. It comes from deceased accident victims who had agreed to the removal. A rejection reaction is unusual.
The donor meniscus is removed under sterile surgical conditions and then tested under internationally accepted criteria for pathogens. The risk of transmission of an infectious disease is extremely low, but cannot be excluded. After appropriate storage and complex transport, the meniscus transplantation is performed minimally invasively during a joint endoscopy. The operation is complex and takes about 2 hours. We are very familiar with the technique of meniscus transplantation since more than 10 years and perform about 15-20 meniscus transplantations per year for private and health insurance patients. All meniscus transplantations are performed by Prof. Siebold.
What is the scientific status and what are the success rates?
Clinical studies show a significant reduction in pain and very good healing of the donor menisci, and most patients do very well with the donor meniscus. Long-term studies also show that the clinical success rate with good cartilage conditions is about 80%. Under certain conditions, additional operations for leg axis correction may be necessary in order to achieve optimal relief of the damaged joint section and the donor meniscus.
Fig.8 Donor meniscus, with marking for better orientation (right).
Fig.9 Cartilage damage without meniscus (left), donor meniscus after implantation (center) and healed donor meniscus (right).
Does it always have to be a donor meniscus? What about synthetic variants?
Because it is often very difficult to obtain a donor meniscus, intensive scientific work focuses on producing a synthetic implant to replace damaged meniscus tissue. The aim is to reduce pain and stimulate tissue growth in a damaged meniscus. The replacement tissue is sutured into the defect area of the inner or outer meniscus so that new, meniscus-like tissue forms and grows in. The implantation is minimally invasive, as a part of a knee joint endoscopy (arthroscopy). Currently, meniscus replacement implants are only suitable for a partial replacement of the meniscus and are not recommended for complete meniscus loss. Two different implants are available on the European market at the moment: “Actifit” and “Menaflex” (formerly: CMI – Collagen Meniscus Implant).
What happens after the surgery, how long does mobilization last?
After partial removal of the meniscus, full weight-bearing can already be performed on the day of surgery, with appropriate joke-oriented transition. One can use forearm walking sticks. Physiotherapy is recommended in the first weeks after the surgery. Office activities can be resumed after about 1 to 2 weeks. In the case of physical activity, it takes a few more weeks before the patient can return to active daily life.
And after the transplant/ graft?
After meniscus transplantation, the partial loading phase is extended to 5 to 6 weeks, otherwise there are no significant differences compared to meniscus suturing. After implantation of meniscus replacement tissue (e.g. ACTIfit), approx. 6 weeks of partial loading are necessary.
Which sports are possible?
After a partial meniscus removal, the knee can be carefully loaded without crutches already on the day of the operation. Cycling is possible after a few days if healing proceeds normally. Swimming follows about 3 weeks postoperatively after wound healing is complete. Jogging and stop-and-go sports (e.g. soccer) are not recommended until three to four weeks after surgery.
What about sports activity after a meniscus suture?
After meniscus suturing, sports rehabilitation can be delayed by several weeks. Here we recommend sports after 4-6 weeks at the earliest. Cycling and swimming are recommended. Movements like squatting should be avoided for at least 3 months to prevent bruising of the meniscal suture. Intensive sports should not be practiced in the 5-6 months after surgery.
And what about sports after a meniscus transplant?
After transplantation of a donor meniscus as well as implantation of meniscus replacement tissue, a return to light sports is possible after 5-6 months. Initially, we recommend cycling and swimming. The return to intensive sports must be carefully considered and is possible after 10-12 months at the earliest.
Through regular clinical checks and a slow build-up of the physical strain, a return to sports is possible in most cases. However, after meniscus transplantation ot the implantation of meniscus replacement tissue, competitive sports are only possible in exceptional cases.
Do you have any further questions?
Would you like to learn more or are you personally affected? Then contact Prof. Dr. Siebold directly. He will be glad to help you.