Symptoms
A tear of the anterior cruciate ligament (ligamentum cruciatum anterius; ligamentum = lat. ligament, anterius = lat. anterior) often makes itself felt at the time of the injury by a noise – similar to a cracking sound – as a typical symptom.
As a rule, the affected person also feels the torn cruciate ligament. Following the anterior cruciate ligament rupture, the following symptoms develop:
- Pain in the area of the knee, since the tear and the subsequent stretching of the articular capsule (Capsula articularis) damages the nerves that mediate the sensation of pain
- Furthermore, in the case of an anterior cruciate ligament rupture, there is instability of the knee, but this only becomes apparent after a few days when the swelling has subsided. In the initial period, the instability resulting from an anterior cruciate ligament rupture is masked by reflective tension of the muscles.
After a few days, an effusion of the knee joint develops in almost every case (approx.
95%) as the most important symptom. Blood accumulates inside the joint capsule, which is called haemarthros. Due to the rupture of the blood vessels supplying the knee joint, it bleeds into the capsule in the event of an anterior cruciate ligament rupture.
This is visible from the outside as a swelling of the knee. When the fluid contained in the knee joint is examined (knee joint puncture), the blood may also contain fatty deposits. This is a sign of an accompanying bony injury to the anterior cruciate ligament rupture, whereby fat is released from the bone marrow of the affected bone, for example from the femur (humerus) or the tibia (tibia).
Alternatively, the fat can also be released as a result of a crush injury to the Hoffa fat body of the knee (lat. corpus adiposum infrapatellare). The Hoffa fat body is a connective tissue structure with fatty tissue parts below the kneecap (lat.
Patella). In addition, an anterior cruciate ligament rupture restricts the mobility of the leg and the affected person is no longer able to move the knee normally. Rather, a person affected by an anterior cruciate ligament rupture assumes a relieving position of the leg: The injured knee is held in a bent position.
When the knee is examined for symptoms of a torn cruciate ligament, a sign typical of an anterior cruciate ligament rupture – the anterior drawer phenomenon – becomes apparent. This manifests itself when the knee is bent by 90 degrees when the examiner pulls the lower leg forward. No movement is possible in a healthy person, but in the case of a torn anterior cruciate ligament, the lower leg can be displaced relative to the thigh.
A similar test is also positive for a torn anterior cruciate ligament. This is the anterior Lachmann test. In principle, it is performed like the anterior drawer test, but in only 30 degrees of flexion.
The described symptoms of an anterior cruciate ligament rupture usually subside after about one week. However, if an anterior cruciate ligament rupture is not treated (cruciate ligament rupture therapy), a permanent instability develops after a few weeks. This is caused by wear and tear of the joint, the capsule-ligament apparatus of the knee, the menisci and the joint cartilage of the knee joint.
The permanent instability after a rupture of the anterior cruciate ligament is called giving way symptomatology. In this case, the affected person’s leg bends away in the area of the knee and the lower leg slips out. The extent of this instability – as well as the impairment of stability at the beginning of the symptoms after a torn anterior cruciate ligament – depends on the strength of the knee joint structures, which include ligaments, muscles and joint capsule.
An anterior cruciate ligament rupture is often accompanied by other injuries. This is the case in about 80% of all patients. Often the inner or outer meniscus or the collateral ligaments of the knee (collateral ligaments) are injured simultaneously.
Other accompanying injuries include damage to the joint cartilage or the joint capsule. Bony tear-out fractures (fracture = break) are also among the concomitant injuries in the case of an anterior cruciate ligament rupture. A typical example is the so-called Segond fracture, which is characterized by a bony tear of the joint capsule at the site of the tibial plateau (upper end of the tibia). A special form of the disease with involvement of the anterior cruciate ligament is the symptom – complication “unhappy triad” (“unhappy triad”).In addition to anterior cruciate ligament rupture, damage to the inner ligament and the inner meniscus is present.
