Tears or ruptures are the most common injury to the menisci
A tearing of the inner or outer meniscus is fundamentally caused by the same thing. For anatomical reasons, the inner meniscus is more often affected than the outer meniscus.
Causes of a meniscus tear
The menisci can be put under high strain if you have an accident – for example, if the knee is bent and loaded, and an uncontrolled rotating movement suddenly occurs. The pressure and simultaneous rotation lead to a shearing movement. This can lead cause the meniscus to tear.
Frequent and severe bending owing to activities involving kneeling, for example, can lead to very small injuries that no longer heal (so-called micro traumas). After months or years, small injuries like these can expand into a large tear. Professional tile or parquet flooring layers are affected, as well as (professional) footballers.
As with all tissues in the human body, the meniscus is also subject to natural wear and tear. The elasticity of the fibrous cartilage decreases and the connective tissue of the menisci loses firmness, becomes adipose or brittle. In these cases, one simple deep knee bend or a rotation of the joint, when getting out of the car for example, can cause a meniscus tear.
Forms of different meniscus tears
The tear can be vertical, horizontal or radial:
- A vertical tear crosses the meniscus from top to bottom and runs parallel to the shape of the meniscus.
- The horizontal tear divides the meniscus into an upper and a lower part. It is also known as a “cleavage” or “fishmouth” tear.
- If the tear stretches from the thin inner edge to the thicker outer edge (base) of the meniscus, it’s known as a radial tear.
Symptoms and signs
A meniscus tear can lead to swelling of the knee joint. If the tear is caused by an accident, there are often additional injuries to the cartilage, lateral ligaments and cruciate ligaments. Damage to the inner meniscus causes pain on the inside of the knee, and damage to the outer meniscus causes pain on the outside of the knee.
- Rotation movements of the joint in an upright position, for example when dancing, doing sport or also during everyday life, are then painful.
- If the person affected cannot stretch out their leg, then this can also be a symptom indicating a meniscus tear: Parts of the torn meniscus can get caught between the thigh and lower leg.
- The knee joint can suddenly give way while walking.
Determining the diagnosis
As well as asking the patient about the duration and nature of the problems, physical examination of the knee joint gives important indications of a possible meniscus injury. As the menisci are soft tissue, they cannot be imaged in an x-ray. Magnetic resonance imaging is therefore a suitable method for establishing a meniscus injury. It also provides additional information about other injuries or damage to the knee.
Therapy: Surgery is often required
Meniscus injuries usually do not heal by themselves. This is because, on the one hand, they are usually in an area of the meniscus that is not supplied with blood. On the other hand, the continuous movement in the knee means that the edges cannot fuse together. Over the course of time, the tears expand and torn meniscus parts can get into the joint and impair its function. This leads to permanent damage on the soft articular cartilage, resulting in increasing joint wear (arthrosis). For this reason, meniscus tears that lead to sustained or recurrent discomfort are usually treated surgically, particularly in young people and active athletes. Increasing age can lead to tearing in the menisci owing to natural wear and tear. But this does not mean that every meniscus tear visible under magnetic resonance imaging has to be surgically treated: If there is no persistent pain, treatment is not necessary. Increasing age can lead to tears in the menisci owing to natural wear and tear.
Meniscus-preserving operation or meniscus substitute
Operative therapy is carried out almost without exception using arthroscopy. As little tissue as possible is removed, to allow the meniscus ideally to retain its function (meniscus partial resection). If complete parts of the wide meniscus base are removed, this is referred to as meniscus resection. This means, however, that the meniscus loses its most important functions, such as load distribution and stabilisation of the joint. The direct loading of the articular cartilage then significantly increases, which leads over the long-term to wear and tear of the joint (arthrosis). This is why the operation should retain the meniscus as much as possible. Tears in the outer parts of the menisci, which have good blood circulation, can in many cases be sutured (meniscus suturing). Particularly with younger patients, it’s worth trying this repair (refixation). In older patients the poorer substance of the meniscus usually does not allow a repair. If the meniscus can no longer be retained, in younger patients, it can be either completely or partly replaced. As with the meniscus suturing, the idea is to prevent premature joint wear and tear.
Braces can promote healing
After a meniscus operation, braces can be used to stabilise the knee, protect it and support the healing of the meniscus. The meniscus suture requires particular protection, because a severe bending of the knee with simultaneous loading leads to high levels of shear forces, which can endanger the meniscus suture. The loading of the knee is therefore usually recommended only in a stretched position.
Modern braces (e.g. M.4 X-lock) support therapy after a meniscus refixation. They have a special locking mechanism to ensure that the knee remains stretched while under strain. The locking mechanism can be unlocked for early functional exercises under no strain. Joint flexibility can therefore be trained at an early stage, which combats muscular atrophy.