Magnetic resonance imaging is considered one of the safest methods of radiation research of tissues. This method uses magnetic radiation, while all other examination devices include the use of x-rays, which can cause adverse effects. What will the knee MRI show? During this procedure, the doctor receives the most accurate information about structural changes or damage, even at the initial stage of the disease.
The principle of MRI
The effect of magnetic resonance imaging is that certain tissues are exposed to radio frequency pulses of various structures and durations. They differ in signal intensity, which affects the degree of contrast when receiving a three-dimensional image.
Liquids are usually characterized by a strong signal, therefore they are colored brightly, but bone tissues have a weaker signal, because of this they appear dark in the image. MRI of the knee is able to show a picture in all planes. Due to this feature, it becomes possible to explore areas such as knee joints that cannot be studied by other types of examinations.
Indications for MRI of the knee
This research method is the only one with the help of which the following diseases are revealed: Glanzmann's myodystrophy, adhesive disease, which arose at the initial stage of the tumor. In addition, MRI is widely used to detect abnormalities of various anatomical structures of the knee - vessels, venous system, nerve trunks.
Thus, the following pathological conditions are indications for the procedure:
- damage to connective tissues (meniscus, tendon);
- tumors;
- fluid in the joint;
- bleeding;
- sports injuries;
- infectious diseases;
- violations with implants and so on.
What can show a picture of an MRI of the knee?
What can show such a study? Thanks to such an examination, quite a few anatomical structures can be seen. The resulting image clearly shows the state of the bone component, as well as nearby tissues. If you compare an MRI image of a healthy knee with an image of an injured joint, you can easily see the problem.
Thus, this type of tomography shows the following elements of the knee:
- Bone tissue. MRI of the knee joint makes it possible to study inflammatory and degenerative changes in the bones, the patella, the head of the joint, fractures, cysts, etc.
- Cartilage. Thanks to such a study, they reveal how worn the cartilage tissue is, and also detect microcracks and tearing of the cartilage.
- Ligaments and tendons. The knee is formed by various elements - muscle tendons, internal, external, posterior and anterior cruciate ligaments, patella. MRI determines their stretching, tears and loss of elasticity.
- Meniscus. The knee joint consists of two types of meniscus: medial and lateral. Often during injuries they rupture, and this can only be detected with an MRI.
Preparation for the procedure
Knee MRI is a diagnostic method for which you do not need to prepare in advance. But still, it is worth considering the following recommendations:
- Scanning and making a large number of images, of which subsequently form a three-dimensional image, lasts quite a long time - about 40 minutes. The patient should lie motionless all this time. In this case, you can ask your doctor for a pillow.
- Induction coils contribute to the creation of not only a powerful magnetic field, but also a loud knock. Suspicious and easily excitable patients may experience discomfort, so it is advisable to use a sedative.
- MRI is performed in a completely enclosed space (tube), so patients with claustrophobia are also advised to take sedatives.
- The contrast agent used in the diagnosis for many people causes allergies, so if you are prone to allergic reactions, you should tell the doctor in advance about this.
- During the study, a powerful magnetic field is created that can damage the patient’s pacemaker or damage tissues containing metal elements (pins, ceramic-metal tooth crowns, staples). In this case, the procedure should be abandoned.
Before the study itself, the patient must remove all metal objects, and his clothes should be free and not restrict movement.
Contraindications
In addition to the fact that a powerful magnetic field destroys pacemakers and damages tissues with iron present in them, there are several more reasons why an MRI of the knee is contraindicated:
- Pregnant and lactating women are not allowed to undergo tomography with a contrast agent, as it is toxic and can be excreted in milk. Also, a magnetic field can adversely affect the fetus, so during pregnancy, MRI is performed only in the most extreme cases, for example, if the mother has a tumor.
- Children under 6 years of age also undergo such a procedure only in special circumstances.
- If the patient weighs more than 120 kg, then he is not allowed to be examined, as he simply will not enter the tomograph.
- If a knee injury causes severe pain, then the person will not be able to lie still, which is the main condition during the examination. In this case, you should abandon the procedure.
- Patients with renal failure are not allowed to have an MRI.
How do they do it?
Many are interested in how to do knee MRI. Magnetic resonance imaging of the knee joint is carried out in the same way as in the study of other organs, only in this case the induction coils will be located at the level of the diseased knee.
The patient rests on a special retractable couch, his position is fixed by pillows and rollers, after which the table is rolled into a closed tube scanner. During the study, the patient should be absolutely motionless, since high diagnostic accuracy depends on this. A tomograph produces a slice every 0.3-0.6 cm, so even the slightest movement is reflected in the results of the examination.
During the session, none of the medical staff will be near the patient, but just in case, two-way communication with the operator is provided. If dizziness, nausea and panic occur, the patient can inform the operator about this.
Many are interested in the question: "If an MRI of the knee is prescribed, how long does it take?" Typically, this procedure lasts from 10 to 40 minutes, and the patient receives the result in his hands 1-2 hours after its completion. But the doctor conducting the MRI can send the result to the specialist who gave the direction.
The use of contrast medium
There are such situations that during the procedure the patient is required to administer an intravenous contrast agent. This method of MRI is called contrast and is used to identify processes that are not visible during the routine diagnosis. Its essence is that the injected drug begins to change the parameters of the surrounding tissues.
Almost all substances are made on the basis of iron oxide and gadolinium, but have different mechanisms of action. Before conducting such a study, they will definitely find out whether an allergy to a contrast medium can occur. Choosing the institution where the MRI of the knee will be performed, you should find out if there is resuscitation equipment there. But complications are very rare.
Which is better - MRI or ultrasound of the knee?
It is necessary to consider these two most popular methods of examination. Ultrasound of the knee joint is performed using ultrasonic waves, and MRI is a computer-aided research method based on the magnetic resonance of compounds of atoms that are part of certain tissues.
Ultrasound is usually recommended for examination of internal organs in order to diagnose their disorders. MRI is used to diagnose bone diseases in the human body.
Ultrasound is also completely safe and practically has no contraindications, regardless of which area is being examined. But when performing MRI, a rather large magnetic field is created, which is why this method of examination has certain contraindications and in some cases it cannot be performed.
Do not forget about the availability of such methods. Due to the simplicity of such a study as ultrasound of the knee joint, its cost is very low, and therefore it is available to all segments of the population. But not many people can afford MRI.
Thus, it is impossible to answer the question of which method for diagnosing the knee joint is better. Therefore, only a specialist can be able to determine the appropriateness of a particular method.
Procedure cost
The cost of an MRI of the knee joint is several times higher than other diagnostic methods. The high cost of the procedure is explained by the high information content of the images, on the basis of which an accurate diagnosis is made.
The cost of an MRI of the knee varies between 3,500 rubles and depends on the intended diagnosis.
Patient Reviews
To many patients, doctors prescribe knee MRI. Reviews indicate that almost everyone was satisfied with this procedure. But not in any clinic, you can go through it, since quite expensive equipment is required. According to patients, the accuracy of the result, the painlessness and safety of the study is what makes the procedure more and more popular every day.
Conclusion
Thus, MRI of the knee joint, although it is considered a safe procedure, but before you go on it, you need to weigh the pros and cons. You can also consult with a specialist in this field. It is also important to find a good clinic where you have an MRI of the knee. It is important that there is resuscitation equipment in it, if the procedure is accompanied by the introduction of a contrast medium.