ACL Injuries

What is an ACL Injury?

The anterior cruciate ligament (ACL) is one of the main stabilising ligaments of the knee. It runs through the centre of the joint, connecting the femur (thigh bone) to the tibia (shin bone), and is essential for controlling rotation and forward movement of the tibia. An ACL injury is a partial or, more commonly, complete tear (rupture) of this ligament.

ACL tears are among the most common significant knee injuries, particularly in sports involving sudden changes of direction, pivoting, jumping, and landing. A torn ACL does not heal back to its original strength on its own, which is why instability can persist after the initial injury settles.

Causes

Most ACL injuries occur without contact — typically during a sudden deceleration, change of direction, pivot, or awkward landing. They are common in sports such as football, netball, basketball, and skiing. They can also occur through direct contact or trauma. ACL tears are frequently accompanied by other injuries, such as meniscal tears or damage to other ligaments or cartilage.

Symptoms

• A “pop” felt or heard at the time of injury
• Rapid swelling of the knee, usually within hours
• Significant pain at the time of injury
• A feeling of the knee giving way or being unstable, particularly when changing direction
• Difficulty returning to sport or activities that involve pivoting

Diagnosis

Diagnosis is based on the history of injury and a clinical examination, including specific tests that assess the stability of the ligament. MRI is the key investigation and confirms the tear while also identifying associated injuries to the menisci, cartilage, or other ligaments. X-rays may be used to exclude a fracture.

Treatment Options

Treatment depends on your age, activity level, the degree of instability, associated injuries, and your goals — particularly whether you wish to return to pivoting sports.

Non-surgical treatment

Some patients, particularly those with lower physical demands or who do not participate in pivoting activities, can be managed without surgery. This focuses on:

• Physiotherapy to build strength and neuromuscular control
• Activity modification to avoid high-risk movements
• Bracing in selected situations

Surgical treatment

ACL reconstruction is commonly recommended for active individuals, those wishing to return to pivoting sport, and those with ongoing instability. The torn ligament is replaced with a graft, and the choice of graft and technique depends on the individual case. The most appropriate approach will be discussed with you at your consultation. (See also the ACL Reconstruction Surgery page for more detail on the procedure.)

Recovery

Where surgery is undertaken, rehabilitation is a substantial and structured process, with return to pivoting sport typically taking many months and guided by both time and functional progress. Where non-surgical treatment is chosen, a dedicated physiotherapy programme is central to optimising stability and function. Your specific plan will be tailored to your circumstances.

Frequently Asked Questions

Can an ACL tear heal without surgery?

A completely torn ACL does not reliably heal back to full strength on its own. Some people manage well without surgery through physiotherapy and activity modification, particularly if they do not participate in pivoting sports, while others require reconstruction to restore stability.

Do I definitely need surgery for an ACL tear?

Not always. The decision depends on your level of instability, activity goals, age, and any associated injuries. Active patients wanting to return to pivoting sports are more likely to be advised to consider reconstruction, while less active patients may do well with non-surgical management.

How long until I can return to sport?

Return to pivoting sport after ACL reconstruction typically takes many months and depends on both healing time and meeting functional rehabilitation milestones, rather than a fixed date. Your surgeon and physiotherapist will guide this based on your progress.

Medical Disclaimer
The information on this page is intended as general patient education and does not constitute medical advice. Every patient is different, and treatment decisions should always be made in consultation with a qualified medical professional based on your individual circumstances, health history, and imaging. Outcomes from treatment vary between patients and cannot be guaranteed. If you have concerns about your knee health, please contact Dr Slattery’s rooms to arrange a consultation.