Menisci

What are menisci ?

Menisci are cartilaginous structures located between the femur and the tibia. The wedge shape of the meniscus and its horn attachments serve to convert vertical compressive forces into horizontal stresses (1). Each meniscus thus resists many different forces such as shear, tension and compression. They also play a crucial role in supporting and transmitting loads, absorbing shocks, and lubricating and nourishing articular cartilage (3)(4)(5). The menisci are thus involved in all movements that mobilise the knee. As vital parts of the joint, they also act to prevent deterioration of the knee structures. Indeed, they slow down the degeneration of the articular cartilage and the onset or development of osteoarthritis (1).

A great deal of research is underway to find alternatives to simple meniscectomies (removal of part or all of the meniscus). The solutions being explored are based on the one hand on in vivo processes by trying to reproduce menisci with the help of stem cells. The main aim would be to incorporate cells that subsequently differentiate into connective tissue and fibroblasts specialised in meniscus function. On the other hand, the solution of cells differentiating with the help of locally injected growth hormones is emerging. On the other hand, research is being carried out into the development of gels or meniscus substitutes that can fulfil the basic functions of the meniscus. However, none of these are ready for application at the moment, but research is continuing, with the aim of one day being able to achieve a less radical and aggressive treatment than meniscectomy… (1)

Anatomically, how are menisci defined ?

The meniscus is a semi-lunar fibrocartilage with little vascularity. Each knee has two menisci, an internal and an external meniscus. They increase joint congruence, stabilise the knee and allow shock absorption and cartilage protection. They are directly linked to the joint capsule but also to the tibia. Thus, it is important to note that the lateral menisci cover a larger portion of the tibial plateau (75-93% laterally) compared to the medial menisci (51-74% medially). Another interesting physiological feature is that the mature meniscus contains blood vessels and nerves only in the peripheral 10-25% of the tissue (2). This is why the inner 1/3 of each meniscus takes much longer to heal after injury or surgery. 

What tests can be used to detect a possible meniscus injury ?

4 simple tests can be performed to try to detect a meniscus injury: 

The tests are positive if pain or discomfort appears and reproduces the usual symptoms. It is essential to always compare the two knees, starting with the healthy side, and to consult a doctor or physiotherapist to confirm the diagnosis, as other factors are also involved. 

• Oudard’s sign: with the patient lying on his back with his knee bent, the practitioner applies pressure with his thumb in the meniscus foci, at the level of the line between the femur and the tibia, to compress the internal or external meniscus. Then, keeping the palpation marks, it is possible to perform a knee extension. 

• Mc Murray’s sign:  The patient lies on his or her back with the knee and hip flexed to 90°. The movement consists of several knee extensions combined with internal rotation (to target the external meniscus) or external rotation (to target the internal meniscus) of the tibia.

• Appley Sign or Grinding Test:  The patient lies prone with the knee bent to 90°. The objective of this test is to apply pressure in the axis of the tibia to compress the menisci. This longitudinal pressure will be combined with internal rotation (to target the external meniscus) or external rotation (to target the internal meniscus).

• Unipodal support and pelvic rotation : The patient stands in unipodal support, knee unlocked and therefore slightly flexed, with his hands on those of the physiotherapist who is in front of him. The aim of this test is to rotate the pelvis and trunk to one side and then the other to compress the menisci. Be careful not to perform rotations at the level of the shoulders, in which case the test will not be representative.  

What treatment should be applied ?

In physiotherapy, the main objectives will be to recover pre-injury amplitudes as quickly as possible in order to be able to start real muscle, proprioceptive and functional strengthening work. Muscular strengthening will mainly target the quadriceps but also the hamstrings and the sural triceps, structures encompassing the knee joint. 

Cryotherapy and cupping sessions can also help with pain and speed of healing. 

The important thing is to always keep in mind the progressiveness, whether it is in the beginning of the rehabilitation or in the resumption of physical activities. 

How can we try to prevent meniscus injuries ?

The prevention of meniscus damage is based on strengthening the structures peripheral to the meniscus. This reinforcement will target the quadriceps, the semi membranous which envelops the external condylar shell, but also the gastrocnemius which originate on the condylar shells of the femur. 

It is obviously advisable to avoid external shocks as much as possible, even though these are uncontrollable events during a match or training session. 

Correct daily hydration allows, although difficult to prove specifically, to provide water and nutrients necessary for the menisci to ensure their proper function. 

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