What is an ACL Rupture?
An ACL rupture is one of the most common knee injuries. ACL stands for Anterior Cruciate Ligament, and is the most commonly injured ligament in the knee joint. The annual reported incidence in the USA in 2023 was 1 in 3500 people.
Below is a summary explaining what the an ACL rupture is, common symptoms, diagnosis and potential treatment.
What is the ACL?
The ACL is 1 of the 2 cruciate ligaments lying deep in the centre of the knee. You have an anterior (ACL) and posterior (PCL) cruciate ligament. Termed ‘cruciate’ due to their ‘X’ orientation. Ligaments attach bone to bone and provide structural stability to joints beyond the dynamic stability of muscle and tendon. The ACL and PCL are the major stabilisers of the knee joint so an ACL rupture can be a significant injury.
Ligaments have strong bands of thick connective tissue mixed with collagen (protein) fibres. Their orientation dictates what stability they provide. The ACL attaches at the top of the tibia (shin bone) near the front, then runs back, up and outwards to attach to the femur (thigh bone) above. It mainly stabilises by stopping the shin bone sliding forward on the thigh bone, as well as side to side and rotational movement.
The ACL is only 3.2cm long and 1cm wide, yet can withhold forces equivalent to over 200kg
How does an ACL rupture?
An ACL rupture usually occurs during a traumatic injury when playing sports, following an awkward fall, or occasionally in a road traffic accident. The most common cause involves multi-directional sports such as football, rugby, hockey or netball. Often sports that require sudden changes of direction with lots of twisting, pivoting and jumping.
As we mentioned above the ACL is an extremely strong fibrous band so this requires and very large, sudden force to cause it to rupture. The mechanism of injury usually involves the foot being planted, slightly flexed, with a sudden rotation or lateral movement.
What are the main symptoms of an ACL rupture?
Commonly symptoms include:
- A loud pop or a “popping” sensation in the knee at the time of injury
- Often painful, and inability to continue activity
- Rapid swelling (varying in amount)
- Loss of range of motion (struggling to straighten and/or kneel)
- A feeling of instability or “giving way” with weight bearing
- Often people describe the knee as “just doesn’t fell right”
How do you diagnose an ACL rupture?
Physiotherapists will often diagnose an ACL rupture through a comprehensive assessment. Detailed, subjective assessment around the mechanism of injury and subsequent symptoms help to set up a the diagnosis. Following this a thorough objective assessment involving physical, hands-on tests can clarify. If an ACL is suspected of being torn then a referral for an MRI scan is considered the goal-standard way of finalising the diagnosis.
Look out for our future blog on the best treatment for an ACL rupture.
Any questions regarding this or any other injury book an appointment here. For any further information please call us on 0114 267 8181 or email [email protected]
