Knee injuries

Knee injuries are common among athletes

The knee injury suffered by Ruud van Nistelrooy is typical of those suffered by footballers, as BBC News Online discovers.

Ruud van Nistelrooy's knee ligament injury is one of thousands suffered by professional footballers each year.

The vast majority of isolated medial ligament injuries heal without an operation

Mr Simon Roberts

The strains put on the knee by the action of twisting and turning put the ligaments - bands of fibrous tissue connecting bones or cartilage and strengthening joints - under tremendous strain.

There are four main ligaments in the knee - one on either side and two across the middle.

The ligament injured in the case of van Nistelrooy is the medial ligament, which runs up and down the inside of the knee.

Former England international Paul Gascoigne's famous knee injury was of one of the cruciate ligaments, which are cross-shaped within the knee-joint.

Mr Simon Roberts, a consultant orthopaedic and sports injury consultant at the National Centre for Sports Injury Surgery in Oswestry, Shropshire, said the problem faced by van Nistelrooy was common.

Top flight footballers

The centre, at Robert Jones and Agnes Hunt Orthopaedic and District Hospital, handles many cases of top flight footballers with damaged knee ligaments each year.

Mr Roberts said: "You can have a minor pull which heals within a few weeks, or a major pull which takes longer. Or it can be completely torn which takes even longer.

"The vast majority of such cases do not require operations, but occasionally people run into chronic trouble."

The medial ligament is linked to the cartilage so further problems can result.

There is some variation in opinion among orthopaedic surgeons about the best way to treat medial ligament injuries, but the vast majority favour allowing them to heal without surgery.

Physiotherapy is used instead, as the medial ligament, being outside the joint, heals more easily than the internal cruciate ligaments.

Mr Roberts added: "The vast majority of isolated medial ligament injuries heal without an operation."

Cruciate injuries, therefore, usually require surgery to repair the damaged ligament and several hundred such operations are carried out at Oswestry each year.