The anterior cruciate is a ligament in the centre of the knee joint that controls rotation and is therefore vulnerable to excessive twisting movements. It can also be injured in large sideways movements of the joint which initially injure the ligaments on the inside or outside of the joint and as the joint opens out excessively, the ACL is also torn.
Not surprisingly, the common sports that produce this injury are football, rugby, skiing and netball, but the ACL can be injured in almost any sport that requires a change of direction while running, or involves physical contact. Women are at greater risk than men with up to 3 times the injury rate in some sports.
The typical story is of a twist while running or landing from a jump, or a blow from the side of the knee. There is often a feeling or hearing of a pop or a snap or something tearing. The player is usually unable to carry on, but may occasionally try and run it off, which is followed by the knee collapsing. The knee then swells within 4 hours. In the UK the story is often then of a trip to casualty, a normal X-ray and a discharge with a piece of tubigrip! The swelling then takes a couple of weeks to settle and a return to activity is possible, but only in straight lines. If an attempt to change direction at speed is made, the knee feels as if it comes apart.
There is a spectrum of symptomatology with at one end a small percentage of patients able to cope quite well, to the other end of the scale where the patient can't turn round in the supermarket without falling over. Undoubtedly there is a high risk of further injury if a return to sporting activity is made. Studies seem to show that reconstructions carried out in the first 6 months following injury have a better prognosis, and the better the state of the joint at the time of reconstruction the better the long term outlook.
Reconstructive surgery generally now involves minimally invasive surgery, taking a strip of the knee cap tendon or hamstring tendon from the back of the thigh and using this tissue to create a new ligament and fix it in the knee, to replace the old ACL. Both types of reconstruction have similar results at 2 and 5 years with a generally accepted success rate of about 90%. Choose your surgeon with care. Studies have shown that in reconstructions that have failed, the cause of failure in 70% of cases is technical error. The best centres report a 5-10% failure rate, so in good hands there is a 90-95% chance of returning to playing sport (depending to a certain extent on the state of the joint at the time of surgery). Surgery does involve the risks inherent to any operation, of deep vein thrombosis or infection, and generally an overnight stay in hospital followed by a phased 6-8 month period of rehabilitation.
Return to sport is generally somewhere between 6-12 months after reconstruction providing rehabilitation has progressed satisfactorily. There has been some publicity about earlier return, but evidence now seems to suggest that this leads to a higher failure rate, as no matter how good the knee feels the healing and remodelling rate of the graft material cannot be speeded up.