Synonyms
posterior cruciate ligament rupture, HKB, HKB rupture, cruciate ligament lesion, posterior knee instability, posterior cruciate ligament insufficiency, chronic insufficiency of the posterior cruciate ligament, cruciate ligament plastic
Definition
A posterior cruciate ligament rupture is caused by exceeding the maximum possible extension of the posterior cruciate ligament, usually by external force. This is a complete rupture, a so-called continuity interruption, of the posterior cruciate ligament, whereby a sagittal (= parallel to the central axis) instability and the so-called drawer phenomenon (= large displacement of the lower leg against the thigh) becomes noticeable.
Cause for cruciate ligament ruptures
In most cases, not only the posterior cruciate ligament is affected by a posterior cruciate ligament rupture. The injuries are usually far more complex and usually affect the entire knee joint, sometimes with enormous adverse effects. Often accidents are responsible for torn posterior cruciate ligaments, and often also car accidents. This is due to the fact that sitting in a car causes the lower leg to bend. If you push it forcibly against it, the rear cruciate ligament tears.
Symptoms
A tear of the posterior cruciate ligament is usually accompanied by typical symptoms that are characteristic of the injury. Immediately after the trauma responsible for the rupture of the posterior cruciate ligament, swelling of the knee and significant pain in the knee joint usually occur. Furthermore, an instability of the affected knee joint is conspicuous, which consists especially in the flexion of the knee joint.
Depending on the extent of the injury and the soft tissue structures affected, bruising and open wounds can occur. Often there are accompanying injuries of other ligaments, bones or cartilage, which is why the resulting pain can only be localized diffusely. During the physical examination, the so-called drawer phenomenon is conspicuous because the knee joint lacks an important fixation due to the tear.
A positive drawer test and a Lachmann test are typical signs of a posterior cruciate ligament rupture. In general, examinations of a knee joint with a fresh ligament injury are difficult due to the severe pain. The pain occurs at the moment of the injury, diminishes, but usually returns when the ligament is strained.
A comparison should always be made with the “healthy” side. The rupture may cause severe swelling and effusions. During the examination, the degree of possible mobility and the meniscus signs must be clarified.
As already mentioned, the medial and lateral ligament stability can be checked by means of the so-called Lachmann test. The drawer test, which is also described, cannot be triggered in the case of an acute injury due to the muscular counter-tension in the acute case. In the case of acute swelling of the knee joint and a knee joint puncture indicated as a result, it can also provide information as to whether a ligament injury in the knee joint is present or not.
If blood from the knee joint is punctured during a puncture, this usually indicates a ligament injury to the knee joint. Often, the diagnosis is only made after the knee joint has become unstable. This can lead to changes in the cartilage and meniscus due to wear and tear.
The diagnosis is made primarily by testing the stability of the knee joint in the extended and flexed positions, in external and internal rotation and in the normal position of the foot. A close examination of the knee with regard to swelling, effusion and the gait pattern is also essential. The neighboring joints should always be examined for clarification and the blood circulation, motor function and sensitivity should be taken into account.
In the case of acute injuries, the stability tests are generally difficult to perform due to the muscle tension, so that further instrumental measures must be taken to make a diagnosis. These are for example:
- X-ray diagnostics: X-ray images in different variations provide information about possible bony lesions.
- Magnetic resonance tomography (MRT): For final clarification whether and to what extent a cruciate ligament rupture is present. With the help of magnetic resonance imaging (MRI), the damage that has occurred can be accurately assessed and any necessary operations can be planned and initiated precisely.
- Assessment of knee swelling, joint effusion, range of motion and motion pain
- Assessment of gait pattern, leg axes
- Evaluation of the femoropatellar joint (sliding bearing of the patella)
- Assessment of knee stability and menisci
- Muscular atrophy (weakening of the muscle relief)
- Assessment of adjacent joints
- Assessment of blood circulation, motor skills and sensitivity (feeling on the skin)
Necessary apparatus examinations X-ray: knee joint in 2 planes, patella (kneecap) tangential Special examination useful in individual cases
- X-ray: Knee joint p. a. in standing position in 45 degree flexion
- Fricke image (tunnel image)
- Captured images
- Whole leg images under load
- Functional images and special projections
- Sonography (meniscus, Baker’s cyst)
- Computer tomography (especially tibial head fracture)
- Magnetic resonance imaging (cruciate ligaments, menisci, bone injury)
- Puncture with synovial analysis (for effusion)
- Automatic drawer testing (not a standard test)
