There are two menisci in the knee. They sit between the thigh bone and the shin bone. While the ends of the thigh bone and the shin bone have a thin covering of soft hyaline cartilage, the menisci are made of tough fibrocartilage and conform to the surfaces of the bones they rest on. One meniscus rests on the medial tibial plateau; this is the medial meniscus. The other meniscus rests on the lateral tibial plateau; this is the lateral meniscus. These menisci act to distribute body weight across the knee joint. Without the menisci, the weight of the body would be unevenly applied to the bones in the legs (the femur and tibia). This uneven weight distribution would cause the development of abnormal excessive forces leading to early damage of the knee joint. The menisci also contribute to the stability of the joint. The menisci are nourished by small blood vessels but have a large area in the center with no direct blood supply (avascular). This presents a problem when there is an injury to the meniscus, as the avascular areas tend not to heal. Without the essential nutrients supplied by blood vessels, healing cannot take place. The two most common causes of a meniscal<unk>  are traumatic injury (often seen in athletes) and degenerative processes, which are the most common<unk>  seen in all ages of patients. Meniscal<unk> s can occur in all age groups. Traumatic<unk> s are most common in active people aged 10–45. Traumatic<unk> s are usually radial or vertical in the meniscus and more likely to produce a moveable fragment that can catch in the knee and therefore require surgical treatment. A meniscus can<unk>  due to an internally or externally rotated knee in a flexed position, with the foot in a flexed position. It is not uncommon for a meniscal<unk>  to occur along with injuries to the anterior cruciate ligament ACL and the medial collateral ligament MCL — these three problems occurring together are known as the "unhappy triad," which is seen in sports such as football when the player is hit on the outside of the knee. Individuals who experience a meniscal<unk>  usually experience pain and swelling as their primary symptoms. Another common complaint is joint locking, or the inability to completely straighten the joint. This is due to a piece of the torn cartilage preventing the normal functioning of the knee joint. Degenerative<unk> s are most common in people from age 40 upward but can be found at any age, especially with obesity. Degenerative meniscal<unk> s are thought to occur as part of the aging process when the collagen fibers within the meniscus start to break down and lend less support to the structure of the meniscus. Degenerative<unk> s are usually horizontal, producing both an upper and a lower segment of the meniscus. These segments do not usually move out of place and are therefore less likely to produce mechanical symptoms of catching or locking. Risk factors The meniscus is made of cartilage, a viscoelastic material, which makes it more susceptible to rate of loading injuries. Repetitive loading can also lead to injury. Recent studies have shown people who experience rapid rate of loading and/or repetitive loading to be the most susceptible to<unk> s. People over the age of 60 who have working conditions in which squatting and kneeling are common are more susceptible to degenerative meniscal<unk> s. Athletes who constantly experience a high rate of loading (e.g. soccer, rugby) are also susceptible to<unk> s. Studies have also shown with increasing time between ACL injury and ACL reconstruction, there is an increasing chance of<unk> s. This study showed<unk> s occurring at a rate of 50–70% depending on how long after the ACL injury the surgery occurred. Meniscal ramp lesions <unk> s of the medial meniscus posterior horn at the menisco-capsular junction) occur in approximately 25% of ACL-injured knees. Lateral meniscal root<unk> s occur in approximately 7% of ACL injured knees
Meniscus tear
Meniscal cyst
Tenonitis
Superior canal dehiscence syndrome
Penile fracture
Discoid meniscus
Infrapatellar fat pad syndrome
Pneumatocele