Ligament injuries in athletes are common especially around the knee and ankle.

What is a ligament?
A ligament is a short band of tough, flexible tissue, made up of lots of individual fibres, which connect the bones of the body together. They can be found connecting most of the bones in the body.

Celtic defender John Kennedy and Arsenal's Robert Pires have suffered.

How?
Twisting, or landing on a knee or ankle that is over-extended.

A heavy landing or awkward turn when the ligaments around a particular joint are at full-stretch can cause it to tear away from the bone.

Or even tear apart.

The four different grades of injury are: