As a rule, the symptoms and medical history (anamnesis) of the accident are already indicative of an external meniscus lesion. In addition, the clinical examination reveals a clear painfulness under pressure over the affected outer joint space. In the case of a joint effusion, this must also be palpated.
There are various clinical tests, so-called meniscus tests, which are positive in case of a meniscus tear and should therefore be tested. In the case of an outer meniscus lesion, pain occurs during internal rotation in this position. In addition, a load from the outside on the outer meniscus causes pain if there is a lesion here.
Since a bony involvement cannot be excluded, an x-ray of the affected knee joint is usually performed in two planes. However, the most valuable diagnostic method is magnetic resonance imaging (MRI in the case of a torn meniscus). This can exclude or confirm an outer meniscus lesion with 95% certainty.
The MRI is a radiation-free examination method with which soft tissues, especially the meniscus and a torn meniscus, can be depicted. – The Steinmann -I- sign describes a passive rotation of the patient by the examiner. This causes severe pain during internal rotation.
- The Steinmann -II sign is positive if a pressure pain occurring in the joint space moves backwards when the knee joint is flexed. – Another test is the Apley-Grinding-Test. In this test, the patient lies on his stomach and the knee joint is flexed by 90°.
Therapy of an external meniscus lesion
As a rule, an arthroscopy (reflection of the knee) is performed after an external meniscus lesion. An arthroscopy offers the possibility of a close examination of the injury and direct therapy. However, this is often difficult and does not always produce satisfactory results.
On the one hand, part of the meniscus can be removed during arthroscopy (meniscectomy). However, this depends on the extent of the injury, as only small parts can be removed. Especially in young patients, attempts are made to suture the meniscus (meniscus suturing).
Due to the good blood supply in the peripheral (outer) third, this is often successful in this area. After the treatment, a long phase of immobilization and very careful re-stressing is often necessary. Overall, sporting activities often have to be reduced.
The quality of the operation and the extent of the partial meniscus removal usually determine the prognosis of an outer meniscus lesion. If the meniscus suture holds sufficiently and the meniscus does not tear out at the suture, the prognosis is relatively good. If, on the other hand, a large part of the meniscus has been removed, arthrosis of the knee joint develops very quickly.
Although the outer meniscus is much less frequently affected by an injury than the inner meniscus, therapy and prognosis do not differ substantially. The outer meniscus can be injured mainly by a strong internal rotation with axial load. With an external rotation the outer meniscus is rather relieved.
Depending on the form and direction of the meniscus tear, different forms are distinguished. Basically, the entire extent of the meniscus rupture determines the therapy and prognosis of the outer meniscus lesion. Smooth tears in the area of the peripheral meniscus can be sutured relatively well, as the blood supply is very good here.
However, if a part of the meniscus is almost completely torn off, often only a partial removal of the affected part remains. The risk of a resulting knee joint arthrosis is then very high.