One of the most common knee injuries is an anterior cruciate ligament sprain or tear. It usually occurs in running ball sports – soccer, football, rugby, netball, and basketball, as well as skiing.

The knee is a hinge joint held together by four ligaments. A ligament is a structure in the knee that holds the bones together and helps to control joint movement or motion. There is a ligament on each side of the knee (the collateral ligaments) and two ligaments deep inside the knee. The two ligaments inside the knee that “cross” each other are called the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Both ligaments attach on one side to the end of the thighbone (femur) and on the other to the top of the shinbone (tibia).

The ACL can be injured or torn in a number of different ways. The most common mechanism is that of a sudden pivoting or cutting manoeuvre during sporting activity, which is commonly seen in football, basketball and soccer. The ligament can also tear due to work injuries or automobile accidents.

So, we know there is a common mechanism of injury.

This mechanism can be a result of two events. A contact event, where another athlete, object, or force puts the knee in a position that causes the ACL to rupture or a non-contact event where the athlete is cutting, decelerating, jumping, or landing that pushes the knee into a position with enough force that it causes the ACL to rupture.

This position of the body for the mechanism of injury is most commonly: Foot planted, knee caves in (knee valgus), hip rotates in (hip internal rotation), and the knee flexes. Although we can get in and out of this position any time we want with no consequence or injury, when combined with high forces or an outside force it has the potential to cause an ACL rupture.

It is important to understand this mechanism in order to understand what can be done to reduce the risk of an ACL injury.

    At the time of the injury, a “pop” or “snap” can sometimes be felt or heard. The amount of pain experienced at the time of the injury is somewhat variable but can be quite severe. Typically, the person is unable to continue play or activity, and has the impression that a significant injury has occurred. Immediate swelling of the knee develops at the time of injury—within the first several hours—but the extent of swelling can be limited if the knee is immediately iced or splinted.

    Treatment options are based on the patient’s symptoms, examination, the growth remaining in his or her growth plates, type of injury to the ligament, and the type of sports and activity goals.


    This would include immobilization or bracing, physical therapy, and a gradual progression back to regular activities and sports.


    Surgical treatment is recommended for individuals with more serious or complete ACL tears. Surgical options may vary based on the type of ACL injury, whether the patient has open or closed growth plates, and the type.

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    Meet Dr Peter Smith, a leading Orthopaedic Surgeon operating from the Mediclinic Milnerton in Cape Town, Western Cape. His practice is situated in the heart of this seaside town.  Dr Peter Smith not only offers patients the full spectrum of professional orthopaedic treatments, but specialises in total knee replacement, total hip replacement, sports injuries and the latest arthroscopic surgery techniques and computer guided surgery. He gained extensive experience in the latest arthroplasty techniques during his stay of 6 years in Australia where he performed more than a hundred primary and revision hip and knee replacements cases in a year.


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