Meniscus injury

Meniscus injury: what’s that?

The meniscus is an elastic, crescent-shaped cartilage disc, which acts as a pressure distributor, shock absorber and stabiliser. Two such cartilage discs are located in the knee joint – the internal meniscus (medial meniscus) and the external meniscus (lateral meniscus). Together with further soft tissue structures they ensure guidance of knee movement, in particular when the knee joint is bent with a slight rotary motion.

At its base, which is on the outer side of the joint, the meniscus has its thickest point and on the inner side its thinnest point. Blood supply follows via the base, i.e. the blood supply diminishes increasingly in the direction of the inside (see Figure).

In the region with no blood vessels, the meniscus tissue is fed via so-called diffusion from the synovial fluid. The greatest degeneration risk and highest susceptibility of tearing exist there. The anatomic structure of the meniscus and the blood supply zones determine the pattern of the injury. This is both decisive for the symptomatic status and for a possible operational procedure.

Injuries or damages to the meniscus are more frequent on the medial meniscus than on the lateral meniscus. Lateral meniscus injuries are often incurred in conjunction with injuries to the ligaments such as injury to the lateral collateral ligament or damages to the cruciate ligament within the scope of (sports) accidents.

Six different meniscus tear patterns are described (see Figure) and their names are related to the course of the tear.

1. transverse tear, 2. longitudinal tear, 3. horizontal tear, 4. abrasion, 5. bucket-handle tear, 6. flap tear

Causes of a meniscus injury

During the course of a lifetime, the menisci are naturally subjected to certain wear and tear. Degeneration already starts from the 30th year of life, i.e. fat is deposited and elasticity lost successively. This degenerative process is also described as meniscopathy and makes the menisci more prone to injuries.

Older patients may already incur meniscus lesions when getting up from a squatting position. Degeneratively pre-damaged menisci can even tear during normal knee movement. Meniscus damages are facilitated by overweight, risk sport types and leg axis malposition (varus or valgus malalignment).

Meniscus injuries are mostly accident-caused amongst young, athletic patients and frequently associated with accompanying injuries to the knee joint. These are traumatic impairments.

Symptoms of a meniscus injury

The symptoms of a meniscus injury can be very varied. They range from an acute joint blockage with inability to bear weight to stabbing pain when making certain movements, but otherwise normal load-bearing. In case of accidents in connection with a strong twisting of the knee, considerable effusion formation and internal bleeding in the joint result. Here, the mobility of the knee is restricted, it is significantly swollen and cannot be burdened.

Diagnosis of a meniscus injury

Initially, a detailed clinical examination is made for diagnostic purposes. Due to the pain of fresh injuries, frequently no classical examination of the knee is possible. However, the course of the accident and observation of the joint with a preliminary assessment provide initial indications. If pain radiates towards the hollow of the knee when it is bent, this confirms the likelihood of meniscus injury.

X-rays and magnetic resonance imaging (MRI) serve to rule-out accompanying osseous injuries. In case of accidents, both menisci and the capsuloligamentous structure may be damaged – e.g. the anterior cruciate ligament and the joint cartilage.

In particular, this is significant for operational procedures. Often, the precise injury pattern cannot be established on MRI. Although severe injuries of the meniscus such as bucket handle or flap tear can mostly be depicted using MRI, it is hardly possible to project the precise extent of horizontal and vertical lesions realistically.  The patient and physician decide jointly regarding operational procedures. Here, both the patient records, clinical examination and imaging as well as the extent of pain and movement restrictions are decisive.

How can meniscus injury be prevented?

No preventive measures for meniscus injury exist. For certain risk sport types with sudden changes of burden such as squash or sport types with external contact, the risk of meniscus injury is very high when older, if overweight or if the training status is poor. When the menisci start to wear, overburdening should be avoided.

What therapy options are available for meniscus injury?

In particular for a so-called bucket-handle tear, the indication for operational treatment is acute. Basically, however, the means of treatment by the physician depends on the patient’s psychological stress and movement restrictions. So-called minimally-invasive arthroscopic meniscus repair surgery is the first-line therapy in case of indication of surgical intervention (pain and movement impairment). This is performed as an outpatient procedure under general anaesthetic, whereby a mini camera is inserted into the joint via a skin cut the size of a buttonhole and the meniscus is treated via a further skin cut (= working access).

For younger patients – i.e. without severe meniscus degeneration – a meniscus tear can be sewn. Modern procedures exist, whereby the part of the meniscus which has been torn off can be tacked. The disadvantage of this meniscus suture is that the use of crutches is required for relief during the 6-week healing phase. The success rate of meniscus sutures is some 70%.

If meniscus suturing is not possible due to the tear pattern and the tissue quality, a partial meniscus removal is made, i.e. the unstable and torn parts of the meniscus are removed. Here, the meniscus root remains intact as full removal of the meniscus should be avoided. The healing phase following partial meniscus removal or a meniscus suture is facilitated by wearing supports and braces .

Minor meniscus injuries with low-level pain can also be treated conservatively with remedial gymnastics, avoidance of risk sport types and wearing a brace.
However, if pain remains after 3-4 months, a meniscus operation is normally inevitable. The success rate for partial meniscus removal is over 90%. Here, careful post-operative treatment plays a decisive role. Post-operative treatment must take the respective patient’s condition into account – regarding the stage of his/her meniscus degeneration and cartilage damage – and be individually adapted to his/her needs.