What is an MRI of the knee joint, how do they show the MRI of the knee joint?

The knee joint is the most vulnerable in the human musculoskeletal system. That is why the diagnosis of knee injuries is an actual problem of traumatology. An ideal method of visualization of the knee joint is magnetic resonance imaging (MRI). With it, you can diagnose various injuries, from ligament ruptures to bone fractures. What is an MRI of the knee joint? How is tomography done? In these matters it is necessary to understand.

Anatomy of the knee joint

This compound is the largest in the human body. The bony bases of the knee are the femoral and tibia, and also the patella. The fibula has nothing to do with the joint. The surfaces of the bones forming the joint are covered with cartilage. Thanks to it, the frictional force is reduced and ease of movement is ensured.

At the distal end of the femur, there are two condyles - lateral (smaller) and medial (larger). They have a rounded shape. The condyle is also at the proximal end of the tibia. They are relatively flat. Between the articulating surfaces there are menisci (external and internal) - crescent cartilages. They stabilize the knee, perform the role of shock absorber in it.

In the knee joint, several ligaments are isolated, which ensure its stability:

• Tibial (medial) collateral;
• Fibular (lateral) collateral;
• Anterior cruciate;
• Posterior cruciate.

The knee also includes tendons. Before considering the MRI of the knee joint, which it shows, it is worth noting that the tendon of the quadriceps muscle is most often damaged. Its rupture is caused by an unexpected contraction of the muscle. Sometimes injuries of a dense and broad tendon or of the ootibial tract are diagnosed. This structure is a strong lateral dynamic knee joint stabilizer.

Indications for MRI

Damage to knee structures is observed quite often. Specialists are mainly addressed by young people who lead an active lifestyle and engage in sports. Before the help, doctors conduct magnetic resonance imaging. This is an accurate and reliable method of diagnosing various injuries.

MRI of the knee joint has certain indications. They include:

• Possible damage of collateral and cruciate ligaments;
• Violation of the integrity of menisci or tendons;
• Suspected fracture;
• Pain in the knee;
• Clarification of information obtained through radiography.

Contraindications to the study

"What will the MRI of the knee and foot show?" - a question, the answer to which can not be sought by all people, because this method of diagnosis has contraindications:

• The presence of an electrocardiostimulator (artificial pacemaker), whose function may be impaired due to the research;
• The metal clips placed on the blood vessels, capable of shifting due to the action of the magnetic field;
• Severe condition of the patient;
• claustrophobia;
• Ferromagnetic implants, because of which the images are not quite correct, the results of the study are distorted;
• Pregnancy before the 12th week.

From this list it is necessary to highlight claustrophobia. It is not an absolute contraindication. When a patient develops a fear of closed and tight spaces, sedative therapy or shallow anesthesia is used.

Conducting research

How the MRI of the knee joint passes is an actual topic for people who are assigned this procedure. So, before performing magnetic resonance imaging, the patient is offered to change into special clothes. You can stay in your things, if they do not have any metal buttons, lightning. Before the research, you also need to remove all jewelry, glasses, watches, remove keys from your pockets, mobile phone.

The scan is performed when the patient is lying on his back. The human feet are placed in the device. During the study, the injured leg is in the radio frequency coil. A healthy limb is parallel to it. Under the leg being examined, a small roller is placed. It is necessary for the best visualization of cruciate ligaments.

If there are suspicions of a tumor, then contrast magnetic resonance imaging is performed. Before the study, a special substance is injected into the patient's vein. It is necessary for the MRI of the knee to show a neoplasm.

MRI-anatomy of the knee joint

To make the correct diagnosis it is important to know that it will show the MRI of the knee joint in the norm. Here is the characteristic of the main components of the knee:

1. Normally, the anterior cruciate ligament on T2-VI and T1-VI appears as a black structure with a homogeneous low-intensity signal. The posterior cruciate ligament on images obtained as a result of MRI is visualized as a well-defined homogeneous black strand.
2. The marginal and tibial collateral ligaments normally give a homogeneous low-intensity signal to T2-VI and T1-VI.
3. Normal menisci on T2-VI and T1-VI are visualized in the form of homogeneously hypo-intensive structures (down to black ones) with central bundles of nerves and vessels. The contours of the meniscus are clear, the surface is uniform.
4. Tendons tend to have a very low signal. They may not even give it at all on images weighed on T1 and T2.
5. Articular cartilage is characterized by low signal intensity on T2-VI and an average signal intensity on T1-VI.

Damage to ligaments

The most commonly injured ligament is the anterior cruciate. What will the MRI of the knee show if this structure is damaged? When the rupture increases the intensity of the signal within the ligament. There may be a discontinuity or a lack of a normal signal. With fresh injuries it is difficult to conclude on the results of MRI on the presence or absence of a rupture, because with a trauma the ligament increases in size (there is edema).

Injury of the collateral ligaments can be a complete rupture, partial tearing and an intraconding rupture. If the tibial collateral ligament proves to be damaged, its thickening will be observed. Areas of signal increase will appear. This is what the MRI of the knee joint shows in the first day. In the future, these areas will disappear due to the absorption of excess fluid in the area of injury by surrounding tissues.

Disorders of the peroneal collateral ligament are diagnosed, as a rule, extremely rarely. Such traumas are combined with massive fractured fractures of the condyle of the tibia, loss of surrounding soft tissues.

Damage to meniscus

With injuries of these structures of the knee joint, the images obtained in the sagittal and coronal planes are considered the most informative. To assess what will be shown by the MRI of the knee joint, and to make a diagnosis, doctors pay attention to the following characteristics:

• The size of the meniscus;
• Their configuration, the nature of the signal;
• Thickness and depth of the changed signal;
• Localization of changes within the meniscus.

There are several degrees of meniscus damage :

1. The first degree is the unexpressed central degeneration. In the course of magnetic resonance imaging, changes are detected within the meniscus. They are manifested by the increased intensity of the signal.
2. The second degree is widespread central degeneration. Inside the meniscus, a wider area of increased signal intensity is visualized.
3. The third degree is the rupture of the meniscus. Inside the meniscus, an increased intensity of the signal is detected. The contour of the intraarticular space is broken. Sometimes the position of fragments of the meniscus changes.

Damage to the tendons

The examination of the tendon of the knee joint is performed in the sagittal and axial planes. In the first of these, the changes are more clearly visualized. The presence of lesions is confirmed if the following MR signs are detected during magnetic resonance imaging:

• Effusion in the tendon sheath (response to excessive congestion) or edema in the peritendinous synovial tissue (in those areas where there is no envelope);
• Thickening or thinning of the tendon;
• Signal change (in case of degenerative pathology in the central zone of the tendon, longitudinally directed radiance is traced, for which a hyperintense signal on T1-VI is characteristic);
• Complete rupture of the tendon (a thickening of scraps of the tendon with a recorded signal intensity and a wavy outline is recorded).

Fractures of bones

Some of the most common injuries are fractures of the bones that form the knee joint. With true fractures, there is a linear decrease in the signal with a rupture of the cortical bone. Sometimes fragments move. There can be hemarthrosis - a hemorrhage into the joint cavity. It appears on the T1-weighted image with a higher signal than the serous fluid.

Particular attention deserves chronic (chronic) fractures, because some people after receiving damage do not seek help from specialists. Such injuries are characterized by hypo-intensive, non-uniform changes with signs of sclerosis of fibrous tissue and bone marrow space.

It is worth considering and contusion lesions (bruises) of the bone. What does the knee MRI show in these cases? With these injuries, there is limited intraosseous edema. It is characterized by a weak diffuse signal decrease on the T1-weighted image and an increase in its intensity on the T2-weighted image. The pathological signal can persist for 3-10 months.

In conclusion, it should be noted that the knee joint is most often injured. One of the best methods for diagnosing various lesions is magnetic resonance imaging. It has several advantages. First, this study is very informative. It allows specialists to assess the condition of bones and soft tissues. Secondly, magnetic resonance imaging is harmless for patients (in the absence of contraindications). That is why MRI of the knee joint is prescribed for children and adults.