What is the knee meniscus?
Menisci are semi-lunar fibrocartilaginous structures located between the femur and the tibia in the knee. There are two menisci – medial and lateral – shaped like the letter C, attached anteriorly and posteriorly to the tibia.
By virtue of their shape, the menisci reduce the incongruence between the joint surfaces of the femur and tibia. In this way they:
- Increase the contact area between the joint surfaces
- Contribute to load transfer
- Reduce pressure on the articular cartilage
- Participate in knee stability
- Distribute synovial fluid within the knee joint
At birth the entire meniscus is vascularised. By the age of 10, the inner two-thirds of the meniscus lose their blood supply, while the outer third retains vascularity – which enables better healing potential after tears.
Meniscal tears in children
It was previously believed that all meniscal injuries in children were related to the discoid form. However, today an increasing number of young athletes present to the paediatric orthopaedic clinic with tears of a normally shaped meniscus.
Meniscal tears are frequently associated with ACL rupture. A torn meniscus loses its physiological protective function, initiating unfavourable processes in the knee – predominantly cartilage damage that gradually leads to degenerative changes and ultimately osteoarthritis.
How is a meniscal tear diagnosed in children?
Meniscal tear is the most common knee injury and accounts for almost 75% of all intra-articular knee pathology. The clinical picture of acute meniscal injury is characterised by:
- Intense pain at the site of the injured meniscus
- Swelling
- Reduced range of motion
Children describe sudden severe knee pain during twisting or extending from a semi-flexed position. A knee block may occur – inability to achieve full range of motion – caused by entrapment of the torn fragment between the bones. The knee then remains in a slightly flexed position with inability to fully extend.
If the meniscal injury is associated with ACL rupture, the event is far more dramatic and children describe the knee "popping out".
Clinical suspicion is further confirmed if specific meniscal tests are positive – all tests involve compression and rotation of the knee to provoke pain at the site of the injury.
Every injured knee should be X-rayed in at least two projections to assess the bones. Since menisci are not visible on X-ray, the imaging study for confirming meniscal injury is MRI, where tear locations can be clearly identified.
Special types of meniscal injury
There are two characteristic forms of meniscal injury:
- RAMP lesion – a specific form of posterior medial meniscal tear at the junction of the posterior meniscal body with the joint capsule. RAMP lesions are frequently associated with ACL rupture and are notable for being very difficult to detect – hence the name "hidden meniscal lesion".
- ROOT lesion – tear of the meniscal root, representing rupture of the fibres that anchor the meniscal ends to the tibia. Such a meniscus no longer has correct biomechanical load distribution, significantly increases contact pressure between the tibia and femur, and accelerates cartilage wear.
How is a meniscal tear in children treated?
The current standard operative technique for meniscal tears is arthroscopic knee surgery with meniscal repair (suturing). The arthroscopic technique begins with inspection inside the joint and confirmation of the meniscal injury.
Once the tear is identified, its character is assessed, the stability of the meniscus is evaluated with a probe, and the surgeon then decides which suture technique to apply. Before suturing, the wound edges of the meniscus or capsule must always be refreshed – especially for older tears – as this triggers biological healing processes in the tissue.
This operative technique should always be applied when treating meniscal tears in children and adolescents. Today, removal of the meniscus – meniscectomy – is considered a "vitium artis" (professional failure) in this age group.
Rehabilitation
Post-operative rehabilitation is essential to allow meniscal healing while preserving range of motion and muscle strength, with the goal of returning children to all activities at the same level as before the injury.
In the early phase of rehabilitation, a knee orthosis is worn; squatting, kneeling and rotational movements are prohibited. Progressive physical therapy subsequently achieves readiness for sporting activities approximately six months after surgery.