Menisci and meniscal injuries
The knee is the most complex mobile joint in the body. Integral to the knee’s functionality and complexity are the menisci, semi-lunar wedge-shaped fibrocartilaginous structures (the lateral and medial meniscus) located between the upper leg (femur) and the lower leg (tibia).
At least two-thirds of the meniscus is thin and avascular (has no blood supply). About 80% of meniscal damage occurs in the avascular area where successful long-term tissue repair is not possible. Many of these injuries are originally sports-related among non-professional, highly active sports players. A sudden twist of the knee, resulting in a pinch or tear of the meniscus, is the usual cause. At present, if the tear is in the non-vascularised area, there is only one surgical option and the damaged tissue is removed by performing a partial meniscectomy. This leads to a permanent reduction in the functionality of the knee joint.
Menisci: mechanical properties
The menisci possess excellent mechanical properties allowing them to act as shock absorbers, lubricant and elastic buffers, and most important to distribute significant forces evenly between the femur and tibia in the knee joint and to ensure overall stability of the knee.
When injuries occur in the vascularised area of the meniscus (about 20% of the time), it is possible to repair the tear by suturing. Even in the vascular zone, this surgical repair fails in approximately 20% of the cases within two years at which stage there is no option but to remove more tissue and to compound the problem. There is overwhelming clinical evidence that removal of meniscal tissue leads to a degenerative condition over time followed by articular cartilage damage, often leading to painful osteoarthritis (bone and cartilage degeneration) and frequently the need for a total knee replacement.