Symptoms
A torn ligament in the knee is a very painful injury. The stabbing and severe pain starts immediately after the rupture event, which is sometimes audible as a “popping” or popping sound. The source of the pain depends on which ligament is torn at the knee.
In addition to the leading symptom of pain, a torn ligament is usually always accompanied by swelling of the knee joint. The swelling can be traced back to an effusion of the joint, which is usually bloody and is therefore also called haemarthros. These two symptoms are very characteristic of a torn ligament in the knee.
The exact structure that is ultimately affected can be determined more precisely by the instability that occurs. Affected persons whose inner or outer ligaments are affected bend inwards or outwards more often. If a rupture of the cruciate ligament is present, some patients feel that the lower leg slides forward under the knee joint.
In general, the loss of stability means that gait insecurity is evident. A torn ligament is usually also accompanied by a restriction of movement. Due to the joint effusion and the associated swelling, the degree of movement is limited. The patient’s own sensation of pain also restricts further mobility and resilience.
Diagnosis
The diagnostic spectrum for torn ligaments in the knee is relatively broad. Before diagnostic equipment such as X-rays or magnetic resonance imaging is used, the clinical examination offers many possibilities to determine whether a torn ligament is present and if so, which ligament is affected. First, however, as with any examination, the inspection and palpation of the knee joint is necessary.
Here, the first important indications of a torn ligament can already be detected: If there is a fresh rupture of the ligament, it often comes to the concomitant symptom of the bloody joint effusion, the so-called haemarthros. An acute haemarthrosis is a swollen, slightly discoloured skin change on the knee joint. The sign of the “dancing patella” can be examined on palpation to detect a joint effusion.
To do this, the doctor uses one hand to stroke the suprapatellar recessus, a bursa, on the patient lying down with the leg stretched out. At the same time, he presses the kneecap (patella) with the other hand, paying attention to a springy resistance, which is indicative of a knee joint effusion. With the various stability tests, there are specific tests for each group of ligaments of the knee joint, with which increased mobility due to a ruptured ligament can be demonstrated and can be performed following inspection and palpation.
The inner and outer ligaments are tested first. The knee is placed under valgus and varus stress. This means the load on the knee including the ligament structures through forces that cause the joint to bend once laterally (= valgus stress) and a second time medially (= varus stress).
When valgus stress is applied, the lateral ligaments are compressed and the medial inner ligaments are stretched and tested for stability. The functionality of the outer ligament is checked with the help of varus stress. Increased “opening” when the ligament is bent hardens the suspicion of a torn ligament.
In addition, pain provoked by the two tests can be an indication of a meniscus lesion. To check the cruciate ligaments, the drawer phenomenon and the pivot-shift test can be performed. The drawer phenomenon is used to check instability in the sense of increased shiftability.
The doctor bends the patient’s knee, sits on the tip of the foot and grasps the lower leg. Now he pulls the lower leg forward once and then pushes it backwards. An anterior instability indicates a rupture of the anterior cruciate ligament, a posterior instability indicates a rupture of the posterior cruciate ligament.
Another test that is positive for an anterior cruciate ligament rupture is the pivot shift test, also called subluxation test. In this test, the lower leg is pressed against the knee and an internal rotation is performed simultaneously under valgus stress. The pivot-shift test is considered positive if there is a painful subluxation, an incomplete dislocation of the tibial plateau anteriorly outward.
If a torn ligament is suspected, imaging of the knee joint is also performed in the vast majority of cases. In this case, an MRI of the knee is best, as the ligament structures are best assessed here. Another test, which is similar to the drawer phenomenon in its execution and which tests the anterior cruciate ligament in the same way as the pivot shift tests the anterior cruciate ligament, is the test according to Lachmann.
In contrast to the drawer phenomenon, the knee joint is not angled at 90° but only at 30°. In this slight flexion position, the shiftability can then also be checked. All these clinical stability tests serve to diagnose a fresh ligament lesion.
If there is a chronic ligament injury, a reduction in the circumference of the thigh muscles is evident. To ensure the suspected diagnosis of a torn ligament, a nuclear spin of the knee is almost always prescribed. In contrast to X-rays, magnetic resonance imaging does not use X-rays, but the magnetic field and radio waves. Torn ligaments can be detected very well with this sectional imaging method. X-rays are more likely to detect bony structures, so an X-ray is often ordered to exclude an accompanying fracture.
