Knee dislocation is uncommon and its main problem is the damage it can cause in ligaments and meniscus.
The symptoms of a knee dislocation are mainly pain and inflammation of the knee.
The doctor will perform an examination to determine if a joint component has been broken due to knee dislocation.
- What is a knee dislocation?
- What types of knee dislocation are there?
- Symptoms of a knee dislocation
- How is a knee dislocation diagnosed?
- Treatment of a knee dislocation
- What is a knee dislocation?
What’s a knee dislocation?
A knee dislocation is a lesion of the knee joint in which the two bony components that form it (the femur and the tibia) lose the joint coupling between both due mainly to a high energy trauma.
Knee dislocations in which the forward or backward displacement of the tibia on the femur occurs are considered traumatological emergencies in which the main problem to be detected in the shortest possible time are vascular lesions, mainly of the artery.
However, although not less important, especially in the medium and long term, they are usually accompanied by breaks in the ligamentous, meniscal and osseous components of the joint.
The dislocation of the knee is a very rare trauma injury, estimated to be around 0.07% of all orthopedic injuries in the human body.
However, numerous recent studies estimate a great loss of cases diagnosed due to traumatic mechanisms where the dislocation of the knee occurs and the subsequent spontaneous reduction of it, making it difficult, therefore, its final diagnosis. In this way it is estimated that knee dislocations present, in fact, a much higher prevalence.
What are the types of knee dislocation?
We can classify knee dislocations according to the evolution time in acute knee dislocations if they are less than 3 weeks from the accident or traumatic mechanism and chronic knee dislocations if they are older than 3 weeks.
From a clinical point of view, knee dislocations can be classified into 5 types:
- Anterior dislocation of the knee: displacement of the tibia above the femur. They account for 40% of all dislocations and are usually accompanied by rupture of the posterior cruciate ligament (PCL).
- Posterior dislocation of the knee: displacement of the tibia below the femur. They account for 33% of cases.
- Internal dislocation of the knee: medial displacement of the tibia with respect to the femur. They account for 4% of knee dislocations.
- External dislocation of the knee: lateral displacement of the tibia with respect to the femur. They account for 18% of all cases.
- Dislocation by rotation of the tibia on the femur: this type of dislocations are a mixture of anterior and posterior displacements with the medial and lateral displacements, they are the least frequent dislocations of all.
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Symptoms of a knee dislocation
People who suffer or have suffered a traumatic knee dislocation have a very inflamed, red knee, which is painful to the touch and pressure and which is generally not able to flex or extend.
Regardless of this, people who have suffered a knee dislocation have had to suffer a high energy trauma that may have caused the bone displacement of the tibia on the femur or vice versa.
The most common mechanisms through which this type of injuries occur are traffic accidents (especially the impact of the dashboard in the knees) if a posterior knee dislocation, a hyperextension mechanism of the knee (in patients precipitated ) in anterior dislocations of the knee and mixed mechanism of rotation of the knee with the same flexion (especially during the performance of sports activities) in which a lateral dislocation usually occurs together with an anterior or posterior rotating dislocation.
If there is vascular involvement due to the mechanism of the lesion, it is possible that they may present pain and decreased coloration in the affected lower limb compared to the previous one.
How is a knee dislocation diagnosed?
In the majority of cases in which a patient suffers a knee dislocation, the doctor finds an inflamed knee, painful on palpation, rigid and deformed by the displacement of the bone components that characterize it.
In cases in which the knee dislocation has reduced spontaneously after the trauma mechanism, the physician should suspect its existence before the finding during the physical examination of joint instability with suspected rupture of at least two of the components of the joint.
In the first place, the doctor in charge of health care must perform a thorough anamnesis in order to find out the type of trauma, the mechanism of action and the force that has caused it. The situation of the patient at the time of the impact or of the mechanism of action also guides the practitioner on the type of injuries he may encounter or suspect.
After the anamnesis or clinical interview, the doctor will perform a complete physical examination of the joint assessing the strength, sensitivity of the knee and distal territories, mobility and angles achieved with the movements as well as the presence of exploratory signs of meniscal lesions. and / or ligaments.
Do knee health questionnaire
If knee dislocation is suspected after this physical examination, an attempt should be made to assess the integrity of the vascularization distal to the lesion, for which it is very important to palpate the intensity and presence of distal arterial pulses and compare them with the contralateral healthy leg.
Before the slightest doubt of vascular alteration in a suspected dislocation of the knee, an imaging test such as arteriography or vascular Doppler ultrasound should be performed to verify the presence or not of vascular lesions inside the knee.
After the corresponding physical and neurovascular examination, the best way to detect adjacent bone lesions and try to elucidate the mechanism of action of the trauma is to perform an X-ray of the affected knee and of the general contralateral in the anteroposterior and lateral views.
Only after the stabilization of the affected knee and having ruled out vascular and neurological pathology can one go on to perform more advanced radiological explorations that improve the diagnosis already suspected through the physical examination, mainly the magnetic resonance.
Treatment of a knee dislocation
Once a traumatic knee dislocation has been diagnosed and maintenance of the vascular and neurological function of the affected limb has been verified, the dislocation must be reduced. For this it is necessary that the patient remains sedated as best as possible to avoid pain and achieve adequate muscle relaxation that allows a reduction as physiological as possible.
The techniques for reducing knee dislocations depend on the mechanism of action of the trauma and the type of dislocation we have.
The final objective will be the repositioning of the bone components in the proper joint harmony, physiological and anatomical.
Subsequently, the knee will be fixed in full extension by placing a plaster splint for at least 2-3 weeks.
The non-urgent posterior treatment of the knee is usually surgical. For a few years now and with the improvement of the effectiveness and efficiency of ligament and meniscus repair interventions by arthroscopy, surgical intervention is recommended in general for the repair of injuries produced by dislocation of the knee.
This type of intervention usually occurs in two different situations depending on the time of intervention. By normal general deferred surgical interventions are recommended around 10-14 days.
The medical objective that is intended with the postponement during this period of time for the surgical intervention is to achieve an affected joint with less intra-articular inflammatory component, with a more consolidated internal structures after the rupture and to enhance the extensor musculature of the knee (quadriceps) that it will improve the postoperative recovery.
In those cases in which, due to the morbidity of the patient, it is not possible to perform the intervention within this period of time, it is usually preferable to prolong the time of surgical intervention until the patient is able to stabilize the knee by conservative methods and intervene in those elements whose recovery It has not occurred under the best circumstances.