Meniscal damages are among the most frequent injuries to the knee joint and make up about 75 percent of the interarticular knee pathology

The importance of the meniscus in the knee joint is best shown by the fact that osteoarthritis (cartilage damage) after meniscectomy (partial or complete removal of the meniscus) is much more common than in the healthy knee which has not undergone a surgery.

Knee menisci are two elastic, crescent, connective-cartilaginous structures that achieve alignment of the femural and tibial articular surfaces (Fig. 1). The menisci are made up of 70 percent water and 30 percent of organic matter, which mostly consists of connective collagen fibres (75 percent). In surface layers collagen fibres are placed radially, in the deep layer they are placed longitudinally or circularly, and in peripheral structures they form a network. Such arrangement of collagen fibres, their waviness and longitudinal twirl provide strength and elasticity to menisci (Figure 1). At birth the fibres are fully vascularised, but by the age of ten the vascularisation is reduced to 10 to 30 percent of peripherals (the section next to the shell) of both menisci.

Thanks to their shape and structure, menisci have important functions in the knee joint. They disperse the load of the entire articular surface of the knee joint, absorb shock, stabilize the ankle, facilitate slidding, (joint movement), improve lubrication of joints, and consequently improve the cartilage nutrition, prevent excessive protrusion and have a proprioceptive role (send feedback to the brain). They overtake about 50 percent of the load, which is transmitted through the knee joint in extension and about 85 percent in flexion of the knee. In case of a partial or complete removal of the meniscus, the contact surface is reduced and the load increases:

  • a partial meniscectomy (only 10 percent of the meniscus) – results in a 65 percent of load increase at the point of contact,
  • a removal of the medial meniscus – results in 50 to 70percent of contact area reduction and increase of the load at the point of contact by 100 percent
  • a complete lateral meniscectomy – leads to 40-50 percent smaller contact area and as many as 200 to 300 percent larger load at the point of contact.
Figure 1 - Shape and position of the meniscus

It is obvious that the function of an intact meniscus is extremely important to preserve the cartilage covering and knee function, i.e. to prevent or to slow down the occurrence of osteoarthritis.

Meniscus injuries are among the most frequent injuries to the knee joint and comprise about 75 percent of the intra-articular knee pathology. They are a consequence of degeneration or trauma, or a combination thereof. A meniscus injury usually occurs by rotation mechanism in a mild flexion. An external rotation mechanism of the lower leg injures the medial meniscus, and an external rotation injures the lateral meniscus. The medial meniscus, especially its posterior horn is four times more frequently injured than the lateral. It is not uncommon that the same mechanism causes knee ligaments injuries, as well as cartilage injuries.

Usually an examination is sufficient to diagnose the injury

A rupture of the meniscus may be transversal, horizontal, longitudinal, inclined, or a combination thereof. In case of a longer longitudinal rupture a free part of the meniscus may “slip” into articulate bodies and block the knee, which, due to that condition, cannot be stretched out. Along with the blockage, other clinical symptoms of a ruptured meniscus are pain at the joint cavity level, slight swelling of the knee joint, and a sense of instability may be present as well.

The diagnosis of a ruptured meniscus is set up by taking of medical history, which is often typical, and a physical examination, which consists of a series of specific, usually not painful, tests. The tests can be supplemented by a magnetic resonance imaging, but only upon examination by an orthopaedist or traumatologist. It is recommended to carry out a native radiographic image of the knee.

Less invasive surgery

The development of arthroscopic techniques and other technical requirements set up the grounds for a minimally invasive treatment of a ruptured meniscus. The first arthroscopic suture was performed by Hiroshi Ikeuchi in 1969. Over time, this method of treatment has become a widely accepted method, so today the treatment of a ruptured meniscus consists of an arthroscopic meniscectomy or a meniscal suture (Figure 2).

Figure 2 - Partial meniscectomy and meniscal suturing view

Meniscectomy

This treatment method means that the knee joint is not opened, but an arthroscope (camera) is inserted through a small opening on one side and a specially designed instrument is inserted on the other side, so only the damaged part of the meniscus is removed. If it is in any way possible, the injured part of the meniscus is sutured (Figure 6) thus preserving its integrity, which is favourable for the subsequent function of the knee joint. For many years the only method of treatment was a partial or total meniscectomy, but soon it was realized that the meniscus does not regenerate, it can only be repaired and can grow up to one third of its normal volume, which is not sufficient for a normal function (Figure 3), thus causing early degenerative changes of the knee (Figure 4). All this leads to conclusion that meniscectomy should be avoided whenever possible, and if it needs to be done, it is recommended to be as minimal as possible, i.e. to remove only a part of the ruptured meniscus (Figure 5).

 

Meniscus sutures

Compared to meniscectomy, suturing is a technically more demanding procedure which prolongs surgery and requires the knowledge of several different meniscus suturing techniques, and assumes the availability of operating instruments as a technical prerequisite. Unfortunately, not all meniscus ruptures can be sutured. To suture ruptured meniscus it is necessary to know its blood supply. Since the blood supply is necessary for healing of a ruptured meniscus, the most suitable for suturing is the peripheral meniscus area, which has the best blood supply. When deciding on meniscus suturing it is important to take into account the type of rupture. Suturing is most appropriate for longitudinal ruptures in the vascular rupture zone and the meniscus and cap joint.

This indication is questionable in case of transversal, horizontal ruptures, ruptures in flap shapes, and various degenerative ruptures. The quality of a meniscus is also important, so it must not be torn or degeneratively altered. Younger patients are most suitable for meniscus suturing (younger than 40, and according to some authors, 50) with a fresh meniscus injury (preferably up to two months old), without injury of cruciate ligaments or with the reconstruction of the anterior cruciate ligament, in case of its rupture. The practice has shown that only 10 percent of the damaged menisci meet the above criteria for suturing.

Figure 3 - Long longitudinal tear of the medial meniscus with incarceration (pinched meniscus); subtotal meniscectomy performed
Figure 4 - Evident knee joint arthrosis 12 years after subtotal meniscectomy
Figure 5 - A small transverse rupture of the outer meniscus body treated with conserving partial meniscectomy
Figure 6 - Incarcerated medial meniscus; repositioned and re-fixed by re-suturing

Regeneration after suturing is complex

There is a significant difference in rehabilitation process after meniscectomy or meniscal suturing. The rehabilitation process after meniscectomy is quick, typically with minimum of pain, and patients can quickly return to full work and sports activities, usually after three to four weeks. But for a sutured meniscus the patient must be motivated, as the postoperative rehabilitation lasts longer. Due to this prolonged healing many professional athletes do not opt for this treatment. The rehabilitation after meniscus suturing consists of limiting flexion and preventing rotation of the knee. In the first two weeks the movement is limited by orthosis to 0/30°, following with 0/50° range in the third week, and after that 0/90°. After four weeks the full flexion is gradually allowed, but squatting and kneeling are forbidden. Walking is permitted immediately after surgery. Rotations of the knee, such as jumping, landing and running with the directional change are forbidden for three months after the surgery. Running without a change of direction is allowed after three months, and a contact sport with rotation six months after the procedure. If there was the reconstruction of the anterior cruciate ligament performed along with the meniscus suturing, then the rehabilitation process does not differ, with respect to accelerated rehabilitation after the reconstruction of the anterior cruciate ligament and an orthosis is not required.

 

Denis Tršek, dr. med., spec. ortoped, AKROMION – Special hospital for orthopedics and traumatology, Krapinske Toplice
Original article published in the Vaše Zdravlje magazine, No.80, year XIII. Front page and article as attachment
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