The knee joint is the most vulnerable in the human musculoskeletal system. That is why the diagnosis of knee injuries is an urgent problem of traumatology. Magnetic resonance imaging (MRI) is considered an ideal method for knee imaging. Using it, you can diagnose various injuries, starting with tearing ligaments and ending with bone fractures. What is knee MRI ? How do tomography? These issues have to be sorted out.
Knee anatomy
This compound is the largest in the human body. The bony base of the knee is the femur and tibia, as well as 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 friction 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. There are condyles at the proximal end of the tibia. They are relatively flat. Between the articulating surfaces there are menisci (external and internal) - sickle-shaped cartilage. They stabilize the knee, perform the role of a shock absorber in it.
In the knee joint there are several ligaments that ensure its stability:
- tibial (medial) collateral;
- fibular (lateral) collateral;
- anterior cruciform;
- back cruciform.
The knee also includes tendons. Before examining an MRI of the knee, 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 muscle contraction. Sometimes injuries of the dense and wide tendon or otibial tract are diagnosed. This structure is a strong lateral dynamic stabilizer of the knee joint.
Indications for MRI
Damage to the structures of the knee are observed quite often. Specialists are mainly addressed by young people who lead an active lifestyle and play sports. Before assisting, doctors perform magnetic resonance imaging. This is an accurate and reliable method for diagnosing various injuries.
MRI of the knee has certain indications. These include:
- possible damage to 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 not all people can search, because this diagnostic method has contraindications:
- the presence of a pacemaker (artificial pacemaker), the function of which may be impaired due to the study;
- metal clips superimposed on blood vessels that can move due to the action of a magnetic field;
- severe condition of the patient;
- claustrophobia;
- ferromagnetic implants, due to which not entirely correct images are obtained, the results of the study are distorted;
- pregnancy until the 12th week.
Claustrophobia is worth highlighting from this list. It is not an absolute contraindication. If the patient is afraid of closed and cramped spaces, sedative therapy or shallow anesthesia are used.
Conducting research
How is an MRI of the knee joint a hot topic for people who are prescribed this procedure. So, before performing magnetic resonance imaging, the patient is asked to dress in special clothes. You can stay in your things if they don’t have any metal buttons, zippers. Before the study, it is also necessary to remove all jewelry, glasses, watches, remove keys from your pockets, and a mobile phone.
Scanning is performed when the patient is lying on his back. Human feet are placed in the device. During the study, the damaged leg is in the RF coil. A healthy limb is parallel to it. A small roller is placed under the examined leg. It is necessary for the best visualization of the cruciate ligaments.
If there is a suspicion of a tumor, then a contrast magnetic resonance imaging is performed. Before examination, a special substance is injected into the patient's vein. It is necessary for the MRI of the knee joint to show a neoplasm.
MRI anatomy of the knee
To make the correct diagnoses, it is important to know what the MRI of the knee joint will show is normal. Here is a description of the main components of the knee:
- Normally, the anterior cruciate ligament on T2-VI and T1-VI looks like a black structure with a homogeneous signal of low intensity. The posterior cruciate ligament in MRI images is visualized as a well-defined homogeneous black strand.
- Peroneal and tibial collateral ligaments normally produce a uniformly low-intensity signal on T2-VI and T1-VI.
- Normal menisci on T2-VI and T1-VI are visualized in the form of homogeneously hypo-intensive structures (up to black ones) with central bundles of nerves and blood vessels. The contours of the menisci are clear, the surface is homogeneous.
- Tendons normally have a very low signal. They may even not give it at all on images weighted by T1 and T2.
- Articular cartilage is characterized by a low signal intensity at T2-VI and an average signal intensity at T1-VI.
Ligament damage
The most commonly injured ligament is the anterior cruciate ligament. What will the MRI of the knee show when this structure is damaged? With a break, the signal intensity inside the ligament increases. Discontinuity or lack of a normal signal may be observed. With fresh injuries, it is difficult to conclude on the presence or absence of a rupture by the results of MRI, because in case of injury the ligament increases in size (edema occurs).
Collateral ligament injury can be a complete rupture, a partial tear, and an intra-ligamentous rupture. If the tibial collateral ligament is damaged, then its thickening will be observed. Signal enhancement areas will appear. This is what the MRI of the knee will show on the first day. In the future, these areas will disappear due to the absorption of excess fluid in the area of injury by the surrounding tissues.
Fractures of the peroneal collateral ligament are diagnosed, as a rule, extremely rarely. Such injuries are combined with massive comminuted fractures of the tibial condyle, loss of surrounding soft tissue.
Meniscus damage
In injuries of these structures of the knee joint, the images obtained in the sagittal and coronal planes are considered the most informative. To evaluate what the MRI of the knee will show, and to make a diagnosis, doctors pay attention to the following characteristics:
- meniscus size;
- 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:
- The first degree is unexpressed central degeneration. In the course of magnetic resonance imaging, changes are detected inside the meniscus. They are manifested by increased signal intensity.
- The second degree is widespread central degeneration. Inside the meniscus, a wider area of increased signal intensity is visualized.
- The third degree is a meniscus tear. Inside the meniscus, an increased signal intensity is detected. The contour of the intraarticular space is torn. Sometimes the position of the meniscus fragments changes.
Tendon injuries
The study of tendons of the knee joint is performed in the sagittal and axial planes. In the first of them, changes are visualized more clearly. Damage is confirmed if the following MR signs are detected during magnetic resonance imaging:
- effusion into the tendon sheath (response to excessive overload) or edema in the peritendinous synovial tissue (in areas where there is no sheath);
- thickening or thinning of the tendon;
- signal change (with degenerative pathology in the central zone of the tendon, a longitudinally directed radiance is observed, which is characterized by a hyperintensive signal at T1-VI);
- complete rupture of the tendon (thickening of fragments of the tendon with a changed signal intensity and a wavy contour is recorded).
Bone fractures
One of the most common injuries is bone fractures that form the knee joint. With true fractures, a linear decrease in the signal with a rupture of the cortical part of the bone is observed. Fragments are sometimes displaced. Hemarthrosis may occur - hemorrhage in the joint cavity. It appears in a T1-weighted image with a higher signal compared to serous fluid.
Particular attention should be paid to chronic (chronic) fractures, because some people do not seek help from specialists after receiving damage. Such injuries are characterized by hypo-intensive, heterogeneous changes with signs of sclerosis of fibrous tissue and bone marrow space.
It is worth considering contusion lesions (bruises) of the bone. What does the MRI of the knee show in these cases? With these injuries, there is limited intraosseous edema. It is characterized by a weak diffuse decrease in the signal in a T1-weighted image and an increase in its intensity in a T2-weighted image. A pathological signal can persist for 3-10 months.
In conclusion, it is worth noting that the knee joint is injured most often. One of the best methods for diagnosing various injuries is magnetic resonance imaging. She has several advantages. Firstly, this study is very informative. It allows specialists to evaluate the condition of bones and soft tissues. Secondly, magnetic resonance imaging is harmless to patients (in the absence of contraindications). That is why MRI of the knee joint is prescribed for children and adults.