Anterior Cruciate Ligament (ACL) Tear
What is a Anterior Cruciate Ligament (ACL) Tear?
The ACL is one of the main stabilising ligaments in the knee, connecting the femur to the tibia. ACL injuries are increasingly common, particularly during pivoting sports such as soccer, tennis, netball, rugby and skiing, and currently affect an increasing number of children and adolescents.
The ACL is in the middle of the knee and controls rotation as well as the forward movement of the tibia bone on the femur bone. If it’s torn, the knee becomes unstable when it is twisted and can give way, as well as losing its full range of movement.
As the knee gives way, the joint surface and meniscal cartilages, frequently become damaged. In 75% of ACL injuries associated damage to the anterolateral ligament or the menisci are encountered. Bruising (oedema) of the bones also occurs at the time of the injury as the femur and tibia collide with each other. The “bone bruising” which is frequently described as micro trabecular fracture does not require any specific treatment.
Mechanism of Injury
The ACL is often injured when the knee is suddenly twisted, for example when a soccer or tennis player changes direction. Another common mechanism is by knee hyperextension (over straightening the joint). Injuries are also common in sports where participants:
• Stop suddenly and change direction, for example during basketball
• Collide with someone, for example knee hyperextension during a rugby tackle
• Land awkwardly from a jump, for example during netball or gymnastics
Symptoms of Anterior Cruciate Ligament (ACL) Tear
When the ACL tears (ruptures) there is often a popping sound, as well as pain and swelling in the knee, usually within an hour of the injury. Patients usually are unable to continue playing sports and hobble for a week or so and then things can settle down.
In around 20% of cases, people with an ACL tear can continue with normal activities. However, most people have ongoing symptoms including knee instability (where the knee gives way, especially when you change direction while walking or running) as well as recurrent pain.
Frequently Asked Questions (FAQ)
In a total knee replacement, the entire knee joint surface is replaced – the ends of the femur (thigh bone), tibia (shin bone), and usually the underside of the kneecap are all resurfaced with artificial components. In a partial knee replacement (PKR), also called unicompartmental knee replacement, only the damaged compartment of the knee is replaced, leaving healthy bone, cartilage, and ligaments intact.
Diagnosis involves understanding a history of your symptoms, examining your knee, and using imaging such as X-rays to assess cartilage wear and joint alignment. In some cases, additional scans such as CT or MRI scans may be required to either exclude other conditions or quantify the degree of arthritis.Some patients develop patellofemoral pain syndrome in the absence of any bone, joint or soft tissue abnormalities. However, most patients with the syndrome present with one or more abnormalities related to bone anatomy, joint anatomy and/or soft tissue.
Although knee arthritis can affect anyone, there are several factors that can increase the risk of arthritis:
- Genetic predisposition
- Previous knee injury or surgery
- Other joint conditions such as rheumatoid arthritis or gout
- Occupations involving heavy manual work
- Age (over 40)
- Female gender
- Being overweight or obese
- Participation in high impact activities or sports (e.g. running, soccer or rugby)
Knee arthritis typically develops as a result of progressive cartilage wear within the joint. This process may occur naturally with age or be accelerated by factors such as previous injury, altered joint alignment, or increased mechanical load.
In some cases, inflammatory conditions such as rheumatoid arthritis can also contribute to joint degeneration.
