Meniscus tear: What should be noted about this type of injury?

The knee joint is a complex joint that is large and bears the entire load of the body. Because of its complex structure, by many components, and its large range of motion, the knee joint is very susceptible to injury. Each time an injury, often causes damage to many components of the joint.

The meniscus is one of the most important components of the joint and is most susceptible to injury. Meniscus tears are common in traffic accidents, sports injuries… So what is meniscus and how is meniscal damage? Please see the article below.

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• I. What is meniscus?
• II. Types of damage to meniscus
• III. Manifestations when meniscus is damaged
• IV. Diagnosis of meniscus tear
• V. Criteria for determining meniscus tear on MRI
• BECAUSE. Treatment and recovery after surgery of torn meniscus

I. What is meniscus?

The meniscus is derived from fibroblasts, which separates the lower end of the femur and the upper end of the tibia.

Anatomy – structure of meniscus

• The knee joint is made up of 3 bones: the lower end of the femur, the top of the tibia, and the patella.
• Each knee has two meniscuses between the head of the femur and the tibia. These are called the internal meniscus and the external meniscus.

Position

• Lined between the lower end of the femur and the top of the tibia are two plates of cartilage with strong, tough, and elastic properties called meniscus. There are two meniscus located inside and outside of the joint called the medial meniscal and the lateral meniscus. Each meniscus has three parts: anterior horns, posterior horns, and midbody; There are two borders: the joint capsule adheres to the joint capsule (peripheral margin), the free border (central border). The inner meniscus is C-shaped, and the outer meniscus is O-shaped.

Notes: A. posterior horn, B. trunk, C. anterior horn; I. rich vascular zone, II. poor circuit, III. circuitless zone

Based on the nature of blood supply, meniscus is divided into 3 regions:

• Area rich in blood vessels: occupies the outer third (joint capsule). This area is full of blood vessels. If this area is torn, it is easy to recover if detected early and treated properly.
• Medial zone: In the middle third, blood vessels begin to gradually decrease. Lesions can heal with correct treatment, but the results are less than the outer third.
• Avascular zone: inner third (free margin), no feeding vessels. If the tear here is irreversible, the tear usually needs to be amputated.

Distribution of blood supply in meniscus

Biomechanics of meniscus

Knee joints bear 5-6 times your body weight while walking. The force acting on the meniscus varies with posture. 50% of gravity is transmitted through the meniscus in the extended knee position, 85% in the flexed knee position. The knee joint with meniscus has the ability to absorb force and shock 20% higher than the knee joint that has been cut meniscus.

The role of meniscus

The meniscus is a C-shaped fibrous cartilage in the knee that functions as a “cushion”. It has the effect of receiving pressure for impact on the knee. It acts as a soft layer between the bones of the knee joint, supporting the stability of the knee joint when moving.

When we walk, run and jump, our knees will have to absorb tremendous forces. At this time, the cartilage layer also acts as a cushion, absorbing strong shock forces, minimizing excess force that damages the undamaged bone surface. Furthermore, thanks to the meniscus, resources from many directions are distributed widely over the entire knee instead of isolating them.

So in summary, the role of meniscus:

• Evenly distribute the force on the knee joint
• Create stability for joints
• Evenly distributes synovial fluid for lubrication and nutrition of joint cartilage.
• Prevent the joint capsule and synovial membrane from getting stuck in the joint space.

II. Types of damage to meniscus

Type of meniscus injury

Meniscus tears in different ways. Description is based on tear morphology, and tear location.

• According to morphology: longitudinal tear, transverse tear, spoke tear, flap shape, beak shape, suitcase handle and complex tear.
• By location: torn anterior horn, posterior horn, body; tear in the avascular area, in the feeding vascular area.

Types of meniscus damage

Causes and mechanism of meniscus tear

In young people:

• Meniscus tears often occur suddenly after an injury in the knee flexed (squat) state and the leg is twisted.
• Common in sports injuries, traffic accidents. Meniscus injuries are often associated with sports, such as football, tennis, or basketball. Even kneeling, deep squatting, or lifting heavy objects can sometimes lead to a meniscus tear.
• These cartilages can tear in any direction, depending on the direction the force is applied.

In the elderly:

• Meniscus tears are often caused by natural degeneration. At the same time, the degeneration on the surface of the femur, becomes more rough. That roughness will tear the meniscus, which has already become softer due to degeneration.
• The patient sits in a chair and stands up suddenly in an adverse position, with the legs slightly twisted, which can also cause meniscal tears. Meniscus tears in the elderly are often accompanied by flaking and wear of the meniscus.
• In these cases, surgery is often indicated.
• The surgery not only repairs the meniscus but also helps repair the damaged joint surface.

>> Exercise brings many benefits to everyone, especially for the group of patients with musculoskeletal diseases. However, due to pain, fatigue or swelling of the joints, many of us do not exercise, gradually weakening the muscles, stiffness, limitation of movement, and ankylosing spondylitis. Proper exercise can help reduce pain and improve quality of life. Along with SignsSymptomsList learn more about this issue through the article: Exercise with musculoskeletal patients

I II. Manifestations when meniscus is damaged

Symptoms of meniscus tear

When you have a sudden injury, strong activity in the knee joint, you may have the following symptoms:

• A "pop" sound can be heard when the meniscus tears.
• Most patients can still walk normally, football players still play the whole game right after the meniscus tear.
• However, after about 2-3 days, the knee gradually swells and feels like a loss of knee flexibility.
• It is possible that after an accident, patients with fluid accumulation in the knee joint can't stand up straight or do normal activities.

Common symptoms of a meniscus tear

• Knee pain.
• Swelling, fluid accumulation and limited knee movement.
• The knee joint is stuck, or there is a clicking sound in the joint when moving.
• The pillow cannot be fully extended

IV. Diagnosis of meniscus tear

Meniscus tear is often the first diagnosis that comes to mind when a patient is admitted to the hospital with a spontaneous injury to the knee.

Doctor's visit

• Diagnosis will become easier when your doctor asks you to move your knees and legs in different positions. Then observe how you walk, raise your knees, and even squat.
• Examination: Press on the joint space of the painful patient; The Mac Murray and Appley tests were positive.
• Meniscus damage is often accompanied by damage to the ligaments of the knee joint. The doctor will review and consider examining the associated lesions.

Diagnostic imaging tools

However, manual examination and medical history alone are not enough. To accurately identify the lesion, the involvement of diagnostic imaging tools is necessary.

The imaging tools commonly used to investigate lesions:

X-ray:

• To assess the condition of the knee joint.
• This is a popular means of quick and easy implementation. However, the value of x-rays in meniscus injuries is rather limited. Because the axial structure of the cartilage is not visible on the x-ray.
• However, this indication can help rule out other knee problems that cause similar symptoms. X-rays can help your doctor look for associated head injuries, especially in older adults.

Knee ultrasound:

• This is a method that uses ultrasound waves to take pictures of the inside of the body. This will determine if you have any loose cartilage that could be stuck in the knee.
• This method can help your doctor examine fluid accumulation around the knee.
• A new method is dynamic ultrasound of the knee joint. This ultrasound is quite cheap compared to MRI. It shows accompanying ligament damage.
• Often this method is used in monitoring the restoration of meniscus and ligaments. Especially the period after surgery.

Diagnostic endoscopy:

• Used when meniscus damage is too complicated.
• Your doctor may use an instrument called an arthroscope to examine the anatomical structures inside your knee.
• The device is inserted through a small incision near the knee. The kit contains a light source and a small camera, which transmits a magnified image from the inside of the knee to the screen. If necessary, surgical instruments may also be inserted. Also through an arthroscope or through other small incisions in the knee to repair the tear.
• Allows viewing of the entire knee joint. Accurately assess the condition and extent of damage to cartilage, ligaments, meniscus, and synovial membrane. From there, it helps to decide on a specific treatment method for each specific case.

MRI images of meniscus lesions

• An MRI (magnetic resonance) machine is essentially a combination of large blocks of magnets. Using frequency magnetic fields and computers to create detailed images of organs and structures inside the body.
• The advantage of this tool is promoted in the diagnosis of diseases in the cartilage, ligaments, tendons, bones or surrounding muscles.
• There is a sensitivity of about 95% and specificity of 81% for the lateral meniscus, and a sensitivity of about 85% and specificity of 93% for the lateral meniscus. MRI is the modality of choice when meniscus tear is suspected and describes most of the features of this lesion.

V. Criteria for determining meniscus tear on MRI

This is the best imaging study to detect a meniscus tear. So this section I will write separately, in order to clarify the important role of this method.

The two most important diagnostic criteria for meniscal tears on MRI are when observed:

1. Meniscus has an irregular shape
2. The meniscus has a high signal intensity but indistinct contact on the surface of the bone head.

Regarding the location and type of tear, MRI imaging of meniscus helps to classify the following types:

• Horizontal meniscal tear

This is the most common type of tear, accounting for 32% of the medial meniscus. Patients with transverse meniscal tears often do not remember the specific injury. Only go to the doctor because the pain in the knee appears or increases more when walking and exercising.

Therefore, the cause of these cases is often attributed to degenerative disease, especially in patients over 40 years of age without the original knee injury.

• Longitudinal meniscus tear

This type of tear shows up on MRI as an elongated tear parallel to the circumference of the cartilage. This is a consequence that is almost always associated with a significant knee injury.

• Radial meniscus tear

This is a case of an annular tear, arising from the free edge of a cartilage and extending into the lumen.

The most common site for this type of tear is in the medial meniscus.

This is because the femur that holds the body's center of gravity slides over the edge of the tibia.

• Complicated meniscus tear

This type of tear is when the meniscus tear does not follow a neat line but tears a flap, spreading in a plane creating separate flaps of cartilage.

Sometimes a torn meniscus flap may move on its own or may be displaced by the transducer during arthroscopy.

• Tear meniscus into cap

The meniscus tear has gone beyond the circumference of the cartilage, forming a loose piece of cartilage that has been displaced from the site of the tear.

The role of knee MRI in this type of tear is important for locating the flap before laparoscopy. It can sometimes be difficult to find the tear because it is displaced during arthroscopy.

If not removed, the torn flap can cause chronic knee pain and jam the knee joint.

BECAUSE. Treatment and recovery after surgery of torn meniscus

• Treatment is complicated, based on careful examination of the injured knee joint.
• In general, depending on the extent of the damage, there will be two types of treatment: conservative (non-surgical) and surgical.
• Post-operative and non-surgical recovery both require an effort on the part of both the physician and the patient.
• Please refer to the treatment and recovery section in our following articles:

>> How long does recovery, treatment and therapy take? When will the patient return to normal activities? With SignsSymptomsList refer to the article:  Treatment and recovery of Meniscus tear

The knee is made up of many different parts. Knee injuries caused by accidents at work, traffic or sports can cause damage to meniscus, ligaments, and ends of bones.

All meniscus tears are characterized by pain, swelling, joint deformity, and limited mobility. Therefore, you should see a specialist as soon as you have a knee injury to be able to accurately diagnose the location of the injury. From there, an appropriate treatment plan is proposed.