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meniscus damage

Meniscus damage

Definition of

Loss of mass or various types of tears in a part of the meniscus; this usually affects the dorsal inner meniscus in the thin „white“, non-vascularized zone. The meniscus is comparatively thick and well vascularized on the outside near the joint capsule (red zone), further inwards towards the articulating joint cartilage there is a less vascularized „white-red zone“, the area far inwards near the joint cartilage is quite thin and no longer vascularized.
The middle area of the meniscus („white-red zone“), which is still slightly vascularized, is much less affected, while the outer meniscus („red zone“) is more affected, although it is still significantly vascularized. This is due to the fact that, in addition to rolling friction and, above all, sliding friction during flexion and extension of the knee joint, axial loads with a combination of this dimension of movement and rotation put a strain on the meniscus.

Arthroscopy ?

If the meniscus is damaged, it may be necessary to resect part of the meniscus if it threatens to become trapped, which can be associated with significant pain. However, any loss of mass increases the risk of osteoarthritis of the knee joint to a greater or lesser extent: removing the entire meniscus, however, increases the risk of osteoarthritis by a factor of over 20. Fairbanks had already pointed out the damaging effect of resection in 1948. Studies published in 1977 (McGinity), 1982 (Gillquist and Oretorp) and 1984 (Allen) also confirmed the clear disadvantages of partial resection. At the latest since Stein, 2010, it has been clear that the long-term prognosis is superior without resection. Even removal of 50% of the meniscus tissue leads to a 70% increase in pressure and to half of the patients having radiographically visible osteoarthritis after just 5 years. After 15 years, the rate is around 100%. In comparative studies, resective arthroscopic intervention is not superior to physiotherapy, but conservative treatment with physiotherapy leads to a better condition of the musculature, which has a protective effect on the knee and its menisci and thus improves the prognosis. The double therapy of surgery and physiotherapy is also not superior to conservative monotherapy, which is usually an argument against it in view of the risks of arthroscopy. All of the available studies relate to patients aged 40 and over. Before this age, tears are mainly caused by trauma. Even after that, some of the tears are caused by trauma, but it is assumed that even minor trauma can lead to a tear in the case of pre-existing degenerative damage later in life. Most tears are triggered by rotations of the lower leg in the loaded knee joint.

Arthroscopic suturing of a torn meniscus, on the other hand, can contribute to a significant improvement in the condition in many cases.

This applies to older years of life and older cracks
and for less vascularized areas,
so that this meniscus-preserving arthroscopy is often worthwhile. Degenerated tissue may have to be removed in older tears. Autologous growth factors from the serum then improve the prospects, e.g. in 30% of all longitudinal tears. Intralesional rasping as a stimulus for the release of growth factors also leads to better healing. The good results of asthroscopic suturing are visible radiologically and even more so clinically. Flap tears with loss of connection to the base of the meniscus and „wear and tear“ have a somewhat less favorable prognosis than other forms. In these cases, a sparing partial resection may be justified if there is a tendency to entrapment.

Meniscus degeneration generally increases with age. In over 70-year-olds, degenerative meniscus lesions can be detected in 50% of cases.

Clinical diagnosis is indicated bytenderness in the joint space(joint line tenderness) and flexor rotation pain. Meniscus damage is sometimes accompanied by joint effusion or painful joint blockages, and Baker’s cysts also occur. The suspected clinical diagnosis is confirmed by MRI.

Types of meniscus tears

1. Radial tear: usually asymptomatic tear from the inner edge along the meniscus radius outwards for some time, but not reaching the outer edge, usually traumatic, often in active young patients. If left untreated, the tear can develop into a parrot’s beak tear, in which the tear continues in a direction parallel to the edge. The unstable area then often leads to recurrent joint effusions, a latching sensation and the Givingway phenomenon
   Flap tear , if it runs parallel to the inner edge after a bend, usually degenerative, from middle age onwards
2. Basket handle tear: Tear line longitudinally through the meniscus – parallel to the main direction of the fibers without connection to the inner edge. The anterior and posterior ends of the fragments are connected to the rest of the meniscus. The free part with the inner edge can dislocate into the intracondylar fossa and cause an extensor lock, which is usually manually reducible and causes a loud pop or click. Combined with pain relief, this is a sign of a successful reduction. Even if this tear still shows the worst healing after suturing, because the tear line is usually in the non-vascularized white zone, it is often promising enough.
3. Horizontal tear: This is a horizontal tear, usually of a degenerative nature, which occurs from middle age onwards. One layer of the meniscus detaches from the underlying layer and can become an unstable flap over time, causing mechanical discomfort. The flap can fold over and become lodged between the articular cartilage.
4. Vertical tear: Vertical, edge-parallel crack line in which the torn part remains connected to the anterior and posterior horn. The vertical crack can develop into a basket handle crack with further detachment.

The classification into grades according to MRI is as follows:

1. a punctiform local signal increase without connection to the surface
2. a) several punctiform local signal increases without connection to the surface and
   b) linear signal increases without connection to the surface
3. Linear or irregular signal increases with connection to the surface, dislocation of fragments, deformation

Meniscus root tears

Root tears of the meniscus (meniscus root tear) are a special case in which one of the four meniscus roots (left/right, anterior horn/posterior horn) is torn or torn off. Although the significant pain experienced during the event later subsides, the affected meniscus(inneror outer meniscus) is far too mobile in the joint with only one anchor, which leads to an increased risk of arthrosisand significantly promotes impingement. This makes the root tear a serious disorder of the knee joint because it is prone to complications. If the meniscus becomes trapped inside the joint, the pain is sharp and shooting; more often, however, it is pushed outwards against the capsule due to the lack of ring tension and causes persistent, diffuse pain. Even tears lead to a pathologically increased flexibility of the meniscus in the joint.

In all cases, the pressure-absorbing surface can be significantly reduced, which significantly promotes wear of the cartilage coating of the bone(osteoarthritis). Only in the case of a posterolateral root tear, in which the meniscofemoral ligament remains functional, is there no increased flexibility and therefore no increased risk of arthrosis. The presence of the meniscofemoral ligaments varies from person to person: The posterior meniscofemoral ligament (Lig. Wrisberg) behind the posterior cruciate ligament in 70% and the anterior meniscofemoral ligament (Ligamentum Humphry) in front of the posterior cruciate ligament in 50%. The more frequent detectability of the ligaments in younger subjects suggests that they tend to degenerate with age.

Tears in and tears of the menisco-tibial ligament insertion and radial tears near the tibial insertion are classified as root tears, as the latter also lead to excessive flexibility of almost the entire meniscus in the joint. In the case of a root tear, the annular tension of the annular meniscus is also lost: axial loading of the meniscus is converted into tensile loading of the annular fibers of the meniscus, which are very resilient to tension, in the case of pyhsiological meniscus anchorsand intact meniscus. If the ring tension is absent, the meniscus yields under pressure to the point of complete ineffectiveness, which means the arthrosis risk of partial or total resection of the area. The most frequent occurrence of root tears is at the two posterior horns (inner and outer meniscus): acute tears are often associated with ligament injuries (in 7-12% of cruciate ligament tears), whereas chronic tears are degenerative, often affect overweight people and are usually localized at the posterior horn of the inner meniscus. Tears at the posterior horn of the medial meniscus mainly affect overweight women over 50 with hindfoot varus. The squatting, cross-legged and kneeling postures common in Asian cultures result in an increased incidence compared to Western countries. In contrast to the inner meniscus root tear, tears of the vascularized and therefore far better regenerating outer meniscus are more traumatic. They are divided into degrees:

1. Root avulsion with intact/intact ligmentum meniscofemorale
2. Radial tear with intact/intact ligmentum meniscofemorale
3. Root avulsion or radial tear with rupture or absence of the meniscofemoral ligament

In principle, MRI is the non-invasive diagnostic method of choice, but a great deal of experience is required to detect tears. Any outward deviation of the meniscus from the joint surfaces must be assumed to be a root tear until proven otherwise. Conservative treatment is not recommended for acute traumatic tears; the meniscus rootshould be refixed and radial tears sutured. In chronic degenerative cases, the meniscus is sutured up to grade 2, after which a partial resection is usually indicated, but only if absolutely necessary. Naturally, sutures on the non-vascularized medial meniscus are less frequently successful. Consequently, a realignment osteotomy must be considered, especially in the case of a varus position of the knee joint(bow leg) that puts a strain on the medial meniscus.

The meniscus root suture is only a case for experienced surgeons. After an operation, partial weight-bearing is initially carried out for 6-8 weeks with forearm crutches. The range of motion is then gradually increased according to pain sensation, whereby 90° flexion should be exceeded after 3 months at the earliest. If the tear occurs together with other damage to the knee joint, the treatment plan must be adapted accordingly. Axial misalignments of the leg such as bow legs may require adaptation of the treatment.

Entrapment

If a meniscus becomes trapped (usually abruptly) and causes significant pain of a stabbing nature, this is not necessarily an indication for prompt arthroscopy, but the meniscus can usually be reduced. However, it should then be clarified why it has become trapped. It is not uncommon for people whose meniscus has already become trapped several times to develop a manoeuvre to reduce it.

ICD M23, S83

Cause

1. degenerative (onset from the age of 40), every person consumes a little of their meniscusresources every day
2. traumatic: the required extent of the triggering event depends on the degree of previous damage, i.e. statistically also roughly on age and use
3. Activities and sports that damage or consume the meniscus

Predisposing

– Axial and static errors

1. Subluxations
2. genu varum (bow leg)
3. genu valgum (X-leg)
4. Buckling foot
5. Pronationor supination tendencywhen running, i.e. hyperpronation or hypersupination
6. Ligament damage
7. Deviation from the leg axis during movements, endorotation of the thigh when bending the knee joint

– muscular factors

1. Lack of strength of the exorotators of the hip joint
2. Lack of strength in the abductors (smaller glutes)
3. Lack of stability and muscular stabilization of the ankle joint

– Behavior

1. Activities and sports that cause rotation in the knee joint. The damaging effect is increased if the knee joint is flexed or extended during rotation.

Diagnosis

1. MRI
2. Tests and signs. All tests are based on pressure pain in the joint space or provocation of a subluxation of the meniscus:
   Steinmann-I: With the knee flexed, the lower leg is rotated. Pain during internal rotation: injury to the outer meniscus, during external rotation: injury to the inner meniscus. Good sensitivity, only moderate specificity
   Steinmann II (Steinmann II sign): When the knee joint is flexed, the pressure pain moves from the front to the back (as the menisci move backwards during flexion ).
   Apley-Grinding test: Rotation with the knee joint flexed, prone position. Pain analogous to Steinmann-I. Good sensitivity, only moderate specificity
   Böhler sign: pain on abduction or adduction ( valgus stress and varus stress) in the knee joint. Good sensitivity, only moderate specificity
   Payr sign: Pressure on the inner side when sitting cross-legged provokes pain Good sensitivity, only moderate specificity
   Joint line tenderness palpation ( painful joint space)
   McMurray test Good sensitivity, only moderate specificity
   Thessaly test
   Hyperflexion and hyperextension pain
   Krömer (only positive for major damage)
   Bragard (only positive for major damage)
   Merke’s sign (only positive for major damage)
   Childress test (duck-walk test)
   Fouche sign (only positive for major damage)
   Quadriceps Active Test / Active Drawer Test
   Eges test
   Chabot sign
   Turner sign
   Tschaklin sign
   Finochietto sign (only positive for major damage)
   Pässler rotation-compression test

Symptoms

1. In the event of entrapment of split-off parts of the meniscus: pain on movement with a stinging sensation
2. Exercise-induced pain
3. also pain at rest with rotation of the lower leg
4. Joint lock if necessary: the extent of the extension deficit and the size of the tear are not proportional

Complications

1. Baker’s cyst
2. Entrapment with joint blockage
3. GonArthrosis
4. Meniscus tear with sudden pain
5. Increased risk of arthrosis, especially of the proximal tibial cartilage

Therapy

1. PT
2. If the meniscus is trapped: reduction with subsequent clarification of the cause
3. Surgery/arthroscopy with suturing, if indicated, also with partial resection. For sutures, the type and location of the tear, activity level and patient compliance are much more important than the patient’s age when determining the indication. In the case of sutures, intralesional and parasynovial rasping can improve healing by stimulating the release of growth factors.
4. Replacement of the meniscus with NUsurface implant if necessary
5. Reproduction of the meniscus with stem cells and growth factors
6. Artificial prosthesis or donor meniscus
7. Improvement of the situation for knock-knees and bowlegs, if necessary corrective osteotomy, also double surgery on tibia and femur
8. Interleukin-1-RA, Orthokine® for osteoarthritis prophylaxis if necessary