KNEE INJURIES

THE anterior crucaite ligament (ACL) is one of four ligaments that stabilise the knee. It runs within the joint cavity of the knee (intra-articular) from the top of the leg bone (tibia) to the thighbone (femur) in an outward direction. It prevents the leg bone from sliding off the thighbone during activities like running or climbing down stairs.

Bundle of collagen

The ACL is a bundle of collagen (connective tissue) about four cm long and one cm thick. It, perhaps, deserves to be termed as the most valuable piece of collagen in the human body as many a high-profile sportsperson's career can be jeopardised by injury to the ACL.

In the last 10 years, there has been tremendous growth of scientific literature on the management of this injury. It is common to sportspersons and in the West, women have a greater incidence than man. This has been attributed to the peculiar anatomy at the end of the thighbone. In India, there is an additional high incidence in men after accidents.

Although there are very few randomised trials concerning surgical management, there have been reasonable studies in the initial assessment, surgical techniques and rehabilitation. Public awareness of the impact of the injury has led many people to seek early surgical treatment.

This is called ACL reconstruction, as attempts to suture the torn ligament have been largely unsuccessful. In an ACL reconstruction, a piece of tissue from the neighbouring tendons and bone (graft) of the patient's own knee (auto graft) is borrowed and fixed with implants. The source of the graft is commonly the patellar (knee cap) or hamstring tendons.

Bone tunnels are drilled in the tibia and femur to site the graft; the graft is threaded through them and is fixed at both ends by some implant (metal or bio absorbable).

Surgical reconstruction is advised in young people who wish to remain active in sports and even in those in whom it is symptomatic even if they are not engaged in sports.

There is no strict age limit or any reason to withhold an ACL reconstruction in a symptomatic individual.

Accurate history

Even consultants miss many ACL injuries. An accurate history should be obtained from the patient. There will be a "popping" sound at the time of the injury.

Immediate swelling ensues after this injury (haemarthrosis or blood collection in the joint). A routine MRI study to support diagnosis in cases of suspected ACL injury is not justified.

MRI has been shown to be less sensitive and specific than an experienced examiner. A MRI is useful in chronic injuries to pick up associated resultant damage to the menisci (semi-lunar cartilages). Concomitant treatment of articular cartilage lesions can logically improve the long-term results after an ACL reconstruction.

Surgical techniques have been refined over the last 10 years. Most knee surgeons now use Arthroscopic or minimally invasive technique. There is some debate about the best source of the graft — patellar tendon or hamstring tendon.

Advances

There is no one answer to this and surgeons should decide on the basis of the patient's needs. Patients whose occupations involve kneeling are not suitable for patellar tendon graft, as there is an increased incidence of anterior knee pain.

New forms of fixing grafts have been developed. These include bio absorbable fixation devices and screws. Early ACL reconstruction is advisable to avoid likelihood of damage to the cartilages of knee and osteo-arthritis.

Ten years ago, it was common practice to splint the knee after an ACL reconstruction. It is now considered unwise to protect the knee and an early return to normal activities is advocated.

Regaining the straight position of the knee is the first goal and regain flexion is the next goal to be achieved progressively. The exercise regime is in an "accelerated" nature and not "aggressive" to avoid strain on the graft.

The physiotherapist needs to supervise the rehabilitation process only on an intermittent basis.