Overview

The ACL (anterior cruciate ligament) is one of two cruciate ligaments located at the centre of the knee, forming part of a complex network of ligaments that give the joint its stability. It's a short, two-bundle ligament connecting the top of the shin bone (tibia) to the base of the thigh bone (femur), and its main job is to stop the tibia from sliding too far forward beneath the femur — providing around 85% of the restraining force against this movement.

What causes an ACL injury?

The ACL is the most frequently injured ligament in the knee, and ACL tears are among the most common knee injuries seen in sport. They typically occur when the knee suddenly rotates or changes direction under load, placing more force on the ligament than it can withstand. This can happen through direct contact — such as a tackle — or, more often, in non-contact situations like landing awkwardly from a jump. Football is the most common cause in men, and netball in women, though ACL injuries also occur in sports involving twisting movements, such as skiing, as well as in everyday accidents like falls or road traffic collisions.

Symptoms

An ACL injury typically causes the knee to swell rapidly — often within minutes — due to bleeding within the joint (known as a haemarthrosis). In the immediate aftermath, it's usually difficult to put weight on the leg, and movement in the knee is significantly restricted because of the swelling and pain. It's important to seek prompt advice from a medical professional at this stage. 

Initial treatment usually involves icing the knee and gently maintaining movement where possible. Swelling and pain generally begin to settle over two to three weeks, with movement gradually improving during this time.

Treatment

The decision to proceed with ACL reconstruction surgery follows a thorough history, examination, and MRI review, alongside a conversation with the patient. Not everyone needs an ACL reconstruction — some patients regain sufficient stability through physiotherapy alone. Whether that's realistic depends on several factors, best discussed with Mr Barkatali.

Surgery is generally recommended when the knee keeps giving way despite physiotherapy — even during everyday activities like walking — or when instability strikes during twisting and turning. It's also advised for those who place high demands on the knee, including professional athletes, high-functioning non-professionals, and people in physically strenuous jobs, where full stability is essential.

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Frequently asked questions

Early clinical assessment by a knee specialist, along with imaging such as an MRI scan, plays an important role in understanding the extent of the injury. In some cases, the ligament may be sprained rather than fully torn, meaning physiotherapy alone can be enough to restore the knee to its pre-injury strength and function.

The ACL is often injured alongside other structures in the knee, such as the meniscus, cartilage, or additional ligaments. An MRI helps identify the full picture, allowing your surgeon to plan the most appropriate course of treatment.

No. Injuries are graded from mild (Grade 1, a slight stretch) to complete (Grade 3, a full tear where the ligament splits into two pieces). Complete tears are the most common type that requires surgical discussion.

Many people describe hearing or feeling a distinct “pop” at the moment of injury, followed by pain, rapid swelling within a few hours, a feeling that the knee is unstable or “gives way,” and difficulty putting weight on the leg.

Some people can walk, and even a few can continue playing briefly, but the knee will typically feel unstable or “loose.” Continuing to put weight or twisting force on it can risk further damage to the cartilage or other ligaments.

It is best to wait until a few weeks after the injury, letting swelling go down and range of motion return first — this is linked to better outcomes than operating on a stiff, swollen knee. Your surgical timeline will be tailored to your specific case by Mr Barkatali.

An unstable knee is more prone to further injury — particularly to the meniscus and articular cartilage — with repeated episodes of the knee “giving way.” Over time, this raises the risk of early osteoarthritis in that knee.

You can’t eliminate the risk entirely, but structured training programmes that focus on jump-landing mechanics, hamstring strength, and balance have been shown to meaningfully lower the odds — particularly for athletes in high-risk sports.

Seek medical attention promptly if you feel or hear a pop in your knee followed by swelling, pain, or a feeling of instability — especially if you can't put weight on the leg. Early evaluation makes it easier to protect the rest of the joint while you decide on a treatment plan.

Please use the link below to make an enquiry and we will be in touch to book an initial appointment with Mr Barkatali.

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