Meniscus injuries: causes, symptoms, diagnosis, treatment

Menisci are fibrocartilaginous structures of a crescent shape. In section they have the shape of a triangle. The thick edge of the menisci faces outward and is fused with the joint capsule, and the thin edge faces inward. The upper surface of the menisci is concave, and the lower surface is almost flat.

The menisci act as shock absorbers for the knee joint, softening impact loads in the joint and protecting the hyaline articular cartilage from traumatic effects. By changing their shape and shifting in the joint cavity, the menisci ensure the congruence of the articular surfaces of the femur and tibia. Bundles of the popliteal and semimembranosus muscles approach the menisci, facilitating their movement within the joint. Due to the connection of the menisci with the lateral ligaments, the menisci regulate the degree of tension of these ligaments.

The circumference of the medial meniscus is greater than that of the lateral meniscus. The internal distance between the horns of the lateral meniscus is two times shorter than that of the medial meniscus. The anterior horn of the medial meniscus is attached to the anterior edge of the articular surface of the tibia in the anterior intercondylar fossa. The attachment site of the lateral meniscus is located somewhat posteriorly, in front of the attachment site of the distal end of the anterior cruciate ligament. The posterior horns of the medial and lateral menisci are attached to the posterior intercondylar fossa of the tibia behind the tubercles of the intercondylar eminence.

The medial meniscus is tightly connected to the joint capsule on its outer surface, and to the deep bundles of the medial collateral ligament in the middle part. It is less mobile than the lateral meniscus. The lateral meniscus is tightly connected to the capsule only in the area of its horns. The middle part of the lateral meniscus is loosely fused with the capsule. The tendon of the popliteal muscle passes through the area of the transition of the posterior horn into the body of the lateral meniscus. At this point, the meniscus is separated from the capsule.

Normal menisci have a smooth surface and a thin, sharp edge. The menisci are poorly supplied with blood. The vessels are localized in the anterior and posterior horns, as well as in the paracapsular zone, i.e. closer to the joint capsule. The vessels penetrate the meniscus through the meniscocapsular junction and extend no more than 5-6 mm from the peripheral edge of the meniscus.

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Epidemiology of meniscus damage

Meniscus tears of the knee joint account for 60-85% of all closed knee joint injuries.

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Symptoms of Meniscus Damage

In case of incomplete longitudinal damage to the posterior horn of the medial meniscus, visual inspection does not reveal characteristic changes. In order to reveal damage, the upper and lower surfaces of the meniscus are examined using an arthroscopic hook. If there is a gap in the thickness of the meniscus, the tip of the probe falls into it. In case of a flap tear of the meniscus, its flap can bend to the posteromedial section or to the medial flank or bend under the meniscus. In this case, the edge of the meniscus looks thickened or rounded. In case of damage at the transition point of the meniscus body to the posterior horn, pathological mobility of the meniscus can be detected when pulling the hook located in the paracapsular zone. In case of a "watering can handle" tear of the meniscus, the central torn part can be pinched between the condyles or significantly displaced. In this case, the peripheral zone of the tear looks narrow and has a vertical or oblique edge.

Degenerative changes in the meniscus occur as a result of age-related changes. They manifest themselves as fraying and softening of the tissue and are combined with a violation of the integrity of the articular cartilage. In chronic long-term degeneration of the meniscus, its tissue has a dull, yellowish tint, and the free edge of the meniscus is frayed. Degenerative tears of the meniscus may not have clinical symptoms. Degenerative tears, like horizontal delamination of the meniscus, are often found in combination with oblique or flap tears. The disc-shaped form of the lateral meniscus is characterized by an unusually wide edge. If the meniscus completely covers the lateral condyle of the tibia, it can be mistaken for the articular surface of the leg. The use of an arthroscopic hook allows you to distinguish the meniscus from the hyaline cartilage covering the tibia. Unlike articular cartilage, when the probe slides along the surface of the meniscus, it is deformed in a wave-like manner.

Classification of meniscus damage

There are different classifications of meniscus tears. The main meniscus injuries are the following: anterior horn tear, transverse or radial, complete or partial meniscus body tear, longitudinal flap tear, longitudinal "watering can handle" tear, paracapsular tear, posterior horn tear, horizontal tear.

Damage to the lateral and medial meniscus is similar in many ways, while longitudinal and flap tears are more typical for the medial meniscus, while horizontal and transverse tears are more typical for the lateral meniscus. Damage to the medial meniscus occurs 3-4 times more often than to the lateral meniscus. Often, both menisci are torn at the same time, but clinical manifestations of damage to one of them predominate. The overwhelming majority of tears occur in the posterior horn of the meniscus. As a rule, an oblique or flap tear occurs in this place. The second most common tear is a longitudinal tear. With a displaced meniscus, a long longitudinal tear can turn into a "watering can handle" tear. In the posterior horn of the internal meniscus, a horizontal dissecting tear is often encountered in patients aged 30-40 years. All of the listed tears can be combined with oblique or flap tears. In the lateral meniscus, transverse (radial) tears are more common. The torn part of the meniscus, while maintaining a connection with the anterior or posterior horn, often shifts and becomes trapped between the condyles of the femur and tibia, causing a blockade of the joint, which manifests itself as sudden limitations of movement (extension), acute pain, and synovitis.

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Diagnosis of meniscus damage

Diagnosis of meniscus damage is made based on the following symptoms.

• Baykov's Symptom. When pressing with a finger in the area of the joint space with the shin bent to an angle of 90°, significant pain appears in the knee joint; with continued pressure and extension of the shin, the pain intensifies due to the fact that during extension, the meniscus rests against the immobile tissue pressed in by the finger. When flexed, the meniscus shifts backward, the pressure decreases, and the pain goes away.
• Chaklin's Symptom. When the medial meniscus is damaged, the tone decreases and the medial head of the quadriceps muscle of the thigh becomes hypotrophic. When the thigh muscles are tense against the background of the medial head of the quadriceps muscle of the thigh, a distinct tension of the sartorius muscle can be observed.
• Apley's Symptom. Pain in the knee joint when rotating the lower leg and flexing the joint up to 90°.
• Land's symptom, or "palm" symptom. The patient cannot fully straighten the affected leg at the knee joint. As a result, a "gap" is formed between the knee joint and the plane of the couch, which is not present on the healthy side.
• Perelman's symptom, or "staircase" symptom. Pain in the knee joint and uncertainty when going down stairs.
• Steimann's Symptom. The appearance of sharp pain on the inside of the knee joint with external rotation of the shin; when the shin is bent, the pain shifts backwards.
• Bragarda's symptom. Pain with internal rotation of the leg and its irradiation to the back with continued flexion.
• McMurray's Symptom: With significant flexion in the knee joint, rotation of the shin (inward or outward) and gradual extension, pain occurs in the corresponding part of the knee joint.
• The "hook" symptom, or Krasnov's symptom. A feeling of fear and uncertainty when walking, a sensation of a foreign, interfering object in the joint.
• Turner's sign. Hypoesthesia or anesthesia of the skin on the inner surface of the knee joint.
• Behler's Symptom: When the meniscus is damaged, walking backwards increases the pain in the joint.
• Dedushkin-Vovchenko's symptom. Extension of the leg with simultaneous pressure with the fingers in the area of the projection of the lateral or medial condyle from the front causes pain on the side of the injury.
• Merke's Symptom. Used for differential diagnostics of damage to the medial and lateral meniscus. The patient, standing, slightly bends his legs at the knee joints and turns the body alternately to one side and then to the other. The appearance of pain in the knee joint when turning inward (in relation to the sore leg) indicates damage to the medial meniscus, but if pain appears when turning outward, it indicates damage to the lateral meniscus.
• Gaidukov's symptom. Presence of fluid in the knee joint. Clearer transmission of transverse shocks in the area of the upper fold during maximum flexion of the tibia (compared to an undamaged joint).
• Payra's Symptom. Pressing on the knee joint with the patient's legs crossed causes sharp pain.
• Rauber's sign. In case of old damage to the meniscus, an exostosis occurs at the upper edge of the tibia.
• Hadzhistamov's Symptom. When the shin is flexed to the maximum at the knee joint and the folds are compressed, the fluid in the cavity moves to the anterior part of the joint and forms small protrusions on the sides of the patellar ligament.

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Treatment of meniscus damage

According to W. Hackenbruch, over the past 15 years, arthroscopic meniscectomy has become the "gold standard" for treating meniscus injuries. Arthroscopy allows for detection, precise determination, and classification of the type of meniscus injury. Low invasiveness of arthroscopic intervention has resulted in a significantly shorter hospital stay compared to open surgery. Previously, open meniscectomy allowed only partial meniscus removal. The current endoscopic procedure allows for partial meniscectomy, i.e. resection of only the damaged portion of the meniscus using special instruments while preserving the functionally important edge of the meniscus, which is necessary for normal joint biomechanics and maintaining its stability, preventing the development of arthrosis.

In young patients in the acute period of injury, arthroscopy allowed meniscus suturing. The most important factor for performing a meniscus suture is the localization of its damage. Ruptures of the peripheral parts of the meniscus, located in the blood-supplied zone, heal better than ruptures of the central parts, where the avascular zone is located.

Arthroscopy has allowed us to reconsider the timing of the start and duration of rehabilitation in the postoperative period. After arthroscopy, early loading of the limb, early development of joint movements, and early return to professional activity are possible.