Biomechanical considerations of the menisci of the knee.

The menisci of the knee are important structures for maintaining a healthy joint since they absorb shock and prevent rotatory instability. The shapes of the menisci and the orientations of their collagen fibres are naturally suited for bearing weight of the joint. Their shape also allows the tibial plateau contact area to be three times greater, thereby decreasing the stress by up to seven times. The medial and lateral menisci are able to move to different extents as a result of the variable laxities of the adjoining ligaments. Often a meniscus becomes injured and must be surgically removed by either a partial or total meniscectomy. Many meniscal injuries occur during sports activities and are caused predominantly by a twisting motion. A meniscectomy has been shown to have detrimental effects including increased joint laxity, osteoarthritis, and other structural changes. Approximately 25% of those who have had a total meniscectomy must stop or restrict their sports activities.