Meniscal tear

The meniscus is a semilunar-shaped fibrocartilagenous structure interposed between the femoral condyles and tibial plateaux.

• lateral meniscus is a “C” shaped structure with a short distance between its anterior and posterior horns while the medial meniscus is “U” shaped and with a larger distance between the two horns
• it is mostly avascular in adults (1)
• the menisci is responsible in transmiting more than 50% of body weight in extension, and even more in flexion. This quality of mensici helps in
  • distribution of stresses over the articular cartilage
  • absorption of shock during axial loading
  • stabilization of the joint in both flexion and extension
  • joint lubrication (2)

Aetiology of meniscal tears can be divided into two groups

• increased force on a normal meniscus
  • usually results from a twisting strain applied to a flexed, weight-bearing leg during sport
  • produces longitudinal or radial tears
• normal forces on a degenerative meniscus
  • usually results in horizontal tears in the posterior half of the meniscus (2)

A torn portion of meniscus may sometimes displace and become jammed between the femur and tibia in the centre of the joint - a 'bucket handle tear'. This may cause a blocking of extension - 'locking of the knee'.

The meniscal tag will act as a persistent mechanical irritant, and will cause recurrent synovial effusion and eventually, secondary osteoarthritis. Medial meniscal tears produce prolonged loss of extension that can stretch and rupture the anterior cruciate ligament.

Reference:

• (1) Nicola Maffulli et al. Meniscal tears. Open Access Journal of Sports Medicine 2010:1 45–54
• (2) Fox MG. MR imaging of the meniscus: review, current trends, and clinical implications. Radiol Clin North Am. 2007;45(6):1033-53