Meniscal injuries are mostly caused by torsional external forces. When a leg is weight-bearing and the lower leg is fixed in semi-flexion with an external booth, the body and the femur rotate violently inward, and the medial meniscus, between the femoral condyle and the tibia, is subjected to rotational pressure, resulting in meniscal tears.
The meniscus is 2 crescent-shaped fibrocartilages located on the medial and lateral articular surfaces of the tibial plateau. Its cross-section is triangular in shape, thick on the outside and thin on the inside, slightly concave on top so as to coincide with the femoral condyles and flat on the bottom, where it meets the tibial plateau. Such a structure precisely allows the femoral condyles to form a deeper depression in the tibial plateau, thus increasing the stability of the spherical femoral condyles to the tibial plateau. The anterior and posterior ends of the meniscus attach to the middle non-articular surface of the tibial plateau, anterior and posterior to the intercondylar spine, respectively. This area can also be referred to as the anterior and posterior angles of the meniscus.
The marginal part of the meniscus is thick and tightly attached to the joint capsule, while the central part is thin and free. The medial meniscus is “C” shaped, with the anterior horn attached before the attachment point of the anterior cruciate ligament and the posterior horn attached between the intercondylar tibial bulge and the attachment point of the posterior cruciate ligament, with the middle of its outer edge closely attached to the medial collateral ligament. The lateral meniscus is “O” shaped, with the anterior horn attached before the ACL attachment point and the posterior horn attached before the posterior horn of the medial meniscus, and its outer edge is not attached to the lateral collateral ligament, which is more mobile than the medial meniscus.
The meniscus can move with the knee joint movement, moving forward when the knee is extended and backward when the knee is flexed. The meniscus is fibrocartilage and has no blood supply of its own. It is mainly nourished by synovial fluid, and only the lateral portion connected to the joint capsule receives some blood supply from the synovial membrane.
The role of the meniscus
Simply put, the function of the meniscus is to stabilize the knee joint, to transmit load to the knee joint, and to promote intra-articular nutrition. It is the stabilizing effect of the meniscus that ensures that the knee joint is not damaged by years of weight-bearing exercise.
1. Weight-bearing
When not bearing weight, the tibia and femur are not in contact and the meniscus pads between them. When weight-bearing, about 70% of the weight-bearing area is on the meniscus, which greatly reduces the stress on the tibial plateau, thus protecting the cartilage and the whole joint.
If the meniscus is removed, the peak pressure on the tibial plateau can rise twofold and will cause cartilage degeneration. It can be inferred that in the case of transverse meniscal tears, the weight-bearing function of the meniscus is completely lost. This requires us to cut as little as possible during partial meniscectomy.
2.Maintain the coordination of knee joint movement
The meniscus moves together with the tibia, the medial meniscus is less displaced than the lateral meniscus, and the meniscus can be deformed during knee flexion and extension to adapt to the anatomical shape of the knee joint. This maintains the coordination of the geometry of the knee joint, thus maintaining the coordination of knee motion.
3 .Maintain stability
Meniscectomy does not cause anterior tibial displacement when the ACL is intact, whereas it causes greater anterior tibial displacement when the ACL is ruptured.
4. Absorption of concussion
In some patients with knee pain, arthroscopic pathology does not reveal any abnormalities, but their symptoms are obvious, and later the meniscus is found to be poorly resorbed.
5, In addition, the meniscus also has the function of lubricating the joint. The meniscus can evenly coat the joint surface with joint fluid, so that the friction coefficient of the joint is greatly reduced.
Etiology of meniscal injury
Meniscal injuries are mostly caused by torsional forces. When a leg is weight bearing and the lower leg is fixed in semi-flexion and external booth, the body and the femur rotate violently inward and the medial meniscus is subjected to rotational pressure between the femoral condyle and the tibia, resulting in meniscal tears. The greater the degree of knee flexion at the time of sprain, the more posterior the tear site is. The mechanism of lateral meniscus injury is the same, but the direction of the force is opposite, and the ruptured meniscus slips partially into the joint, causing mechanical obstruction to joint activities and preventing joint extension and flexion activities, forming “interlock”.
Meniscus injury
Meniscal injury can occur at the anterior, posterior, middle or marginal part of the meniscus. The shape of the injury can be transverse, longitudinal, horizontal or irregular, or even broken into intra-articular free bodies. The classifications are: marginal tears, transverse tears, longitudinal tears, horizontal tears, and anterior and posterior corner tears. In severe trauma cases, the meniscus, cruciate ligament and collateral ligament can be damaged at the same time.
After a meniscal injury, there is severe pain in the knee joint, inability to straighten itself, and swelling of the joint. Pressure pain at the knee joint space is an important basis for meniscal injury.
Diagnosis of meniscus injury
1.Most patients have a history of knee sprain.
2.There is a popping sound in the knee when extending and flexing the knee joint.
3.There is tearing sensation and ringing sound in the knee joint at the time of injury, that is, severe pain, joint swelling and dysfunction of flexion and extension activities occur. The pain of knee movement is obvious when walking and going up and down stairs, and some patients may have a weak leg and strangulation of the knee.
4. The examination may reveal quadriceps atrophy, pressure pain in the knee joint gap, and inability to hyperextend or hyperextend the knee joint.
5, meniscus popping test (McSweeney’s sign): the patient lies on his back, fully bend the hip and knee, the examiner holds the foot with one hand, the other hand on the knee, first make the calf inwardly rotated, then abducted and straightened, then make the calf externally rotated and abducted, then inwardly straightened, if there is pain or popping is positive. Most of the patients are positive.
6.Grinding test: The patient is in prone position, the affected knee is flexed at 90°, the examiner presses down hard on the ankle and does rotational grinding, and it is positive when there is pain in a certain position.
Meniscal injury tests
The purpose of radiography is not to diagnose meniscal tears, but to rule out osteochondral free bodies, exfoliative osteochondritis and other knee disorders that may be similar to meniscal tears. Arthrography is a valuable adjunct to the analysis of knee disorders. However, because of modern non-invasive and highly accurate examinations such as MRI, imaging techniques are now less commonly used.
2, MRI is by far the imaging means with the highest positive sensitivity and accuracy in diagnosing meniscal injury and cruciate ligament rupture, with an accuracy rate of 98%. MRI of meniscal tears shows a low signal meniscus with linear or complex shaped high signal bands across the surface of the meniscus.
Other diagnostic imaging methods such as high-resolution ultrasound and high-resolution CT of the knee joint are also helpful in the diagnosis of intra-articular disorders of the knee.
3. Arthroscopy Arthroscopic techniques have been recognized as the most ideal means of diagnosis and surgical management of meniscal injuries. However, arthroscopy should not be the routine means of examining meniscal tears. Only after the clinical diagnosis of meniscal tears is made, arthroscopy is used to confirm the diagnosis and to perform arthroscopic surgery at the same time. The superiority of arthroscopy can be demonstrated only after the initial clinical diagnosis of meniscal tears has been made.
Treatment of meniscal injuries
Many studies have been conducted on the biomechanical function of the meniscus, and the importance of the biomechanical function of the meniscus has been increasingly recognized. It is believed that it is not advisable to simply remove the damaged meniscus, but to repair them. It is one of the problems in the orthopedic field that meniscal injuries without blood supply do not heal easily after repair, and many studies have been conducted for this reason.
1.Acute stage If the joint has obvious fluid (or blood)
If the joint is “interlocked”, the “interlocking” should be released by manipulation, and then the knee joint should be fixed in the straight position for 4 weeks with a tubular cast from the upper 1/3 of the thigh down to the ankle. The cast should be properly shaped so that the patient can walk with the cast on the floor. During the fixation period and after the removal of the fixation, the quadriceps should be actively exercised to prevent muscle atrophy.
2.Repair of meniscus blood supply area injury
Injuries to the blood supply area of the meniscus, especially longitudinal lacerations, can be healed by suturing surgery, which has a good prognosis, as confirmed by many experimental and clinical studies.
3.Repair of meniscus injury without blood supply area
Injuries to the meniscus without blood supply are relatively difficult and have become a challenge in knee surgery. Smaller and regular injuries of the meniscus without blood supply, such as barrel stem-like tears, are often treated with partial resection with fair results, but this compromises the biomechanical and biophysical function of the meniscus to a greater or lesser extent. Although many methods have been found to deal with meniscal injuries without blood supply, clinical studies have been conducted less frequently, and this area needs to be explored.
4.Severe meniscus injury
When the meniscus is severely damaged, only total resection surgery can be performed. At this time, frozen meniscus and meniscus prosthesis transplantation are feasible, but there are many difficulties in meniscus prosthesis transplantation, such as the biomechanical function of the prosthesis cannot meet the requirements, the prosthesis is difficult to fix, and joint degeneration is still obvious after transplantation.
5.Surgical treatment
Surgical treatment mostly refers to the use of arthroscopy to remove the free meniscus fragments, or to remove the damaged meniscus. However, no matter which treatment plan is used, the meniscus should be preserved as much as possible, trimmed or sutured as much as possible, or the meniscus should be preserved as much as possible under the premise of maintaining the stability of the residual meniscus to reduce biomechanical changes. However, if a severely damaged meniscus is not treated with surgery as early as possible, the damaged meniscus will wear away the articular cartilage, which in turn will cause degeneration of the joint. It is like a bearing with a broken ball inside, and everyone should know what to do with it.
6.Meniscus regeneration
A more desirable treatment than surgical treatment is to allow the meniscus to regenerate. Since the 80’s, the use of pure natural sawtooth shark cartilage powder has been popularized in advanced countries such as Europe, America and Japan as an alternative therapy for knee meniscus injuries.
It is the best way to treat meniscus injuries by restoring the meniscus to regenerate. The purely natural Sawtooth shark (i.e., the great blue shark) cartilage powder can realize the regeneration of human cartilage and completely regenerate the meniscus from the inside, which has become a brand new attempt in advanced countries and has been gradually promoted to the clinic in the world. However, the difficulty of selecting materials for this therapy, the high technological requirements and the relatively high price are an obstacle to its widespread popularity.
The usual points to note
1, diet less greasy, high fat, more vegetables and fruits, less fine grains, more coarse grains.
2.When going up and down the stairs, you must pay full attention and step steadily before moving the second step to avoid trauma.