Degenerative tears are a result of the natural aging process, as over time the meniscus loses its elasticity (similar to your skin) and becomes harder. This makes it more likely to tear.  These tears may be purely incidental findings on scans and may not cause any problems.

Acute tears of the meniscus occur as the result of an injury to the knee.  These are may be associated with other injuries such as ACL injuries or articular cartilage injuries.  It is vital that your knee is assessed correctly for other injuries as they often require combined treatment.  These tears typically heal well after repair, and it is advisable to be seen as soon as possible to start the healing process and prevent further injury.  

The meniscus can tear in various ways(see image at right), they can be A: Horizontal B: Radial C: Longitudinal D: Flap E: Parrot Beak F: Bucket Handle.

The pattern of the meniscal tear will ofter determine if or how the meniscus can be repaired.  In many cases in a healthy meniscus, the meniscus can be sutured back together using keyhole surgery.  For more complex tears with good meniscal tissue, sometimes arthroscopic assisted surgery may be required (this involves an incision on the side of the knee as well as the keyhole surgery).  If the meniscus is degenerative, or if it is unable to be repaired then the torn portion of the meniscus may need to be removed as it will not heal.

If small parts of the meniscus are removed, this will not substantially affect the knee; however if large sections of the meniscus are removed, it increases the force through the cartilage of the knee, and this can result in early osteoarthritis of the knee.  Therefore, wherever possible, Dr Slattery tries to repair the meniscus to preserve the shock-absorbing function of the knee and prevent arthritis.