What is an anterior cruciate ligament (ACL) injury?

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What is the ACL?

The anterior cruciate ligament (ACL) is one of the main ligaments in the knee joint. It connects the thigh bone (femur) to the shin bone (tibia), as seen below:

The ACL is a rope-like structure that mainly functions to prevent the tibia from sliding out in front of the femur, and it also resists twisting.

How does the injury occur?

ACL injuries mostly occur during sports such as football, netball, and basketball. This is because such sports involve many start-stop movements, changes of direction, and speed changes. They sometimes occur during simple falls or even at work.

The usual way this happens is when a sudden twist happens when the foot is planted on the ground. There is usually a sudden painful pop, and very frequently the patient falls down.

Signs and Symptoms

If you suspect that you have an ACL injury, here are some possible signs and symptoms which you can look out for:

  • Painful ‘popping’ noise, right when the injury occurs

  • A feeling that your knee is giving way (losing stability), significantly when changing direction
  • Intense pain and immediate swelling of the knee joint
  • Difficulty with putting weight on the injured leg
  • Discomfort or inability to walk
  • Range of motion becomes limited

What does this mean to the patient?

If left untreated, an ACL injury can significantly impact the patient’s activities, especially those that involve sports. It can result in pain, discomfort, and instability in movement. Most athletes will find themselves unable to return to their sport of choice.

In the long term, an unstable knee caused by an ACL injury can result in the knee wearing out faster than usual. This may necessitate further treatment, which can include more extensive surgery.

Assessment and Work-up

To diagnose an ACL injury, your doctor may conduct physical assessments alongside other tests. The doctor may also ask questions about how you got the injury and your medical history.

Your doctor may demonstrate that the knee is unable by pulling on the shin bone, where a torn ACL would lead to the shin bone shifting towards the doctor abnormally. This is known as the anterior drawer test.

The most important part of the assessment is frequently an MRI scan. This scan is useful as it allows the doctor to assess the status of the ACL, as well as other parts of the knee joint without any form of surgery.

An ACL tear may also coexist with other knee injuries, such as fractures, cartilage injuries, and injuries to other ligaments in the knee.

Treatment Options

For treatment of an ACL injury, the recommendation is for all fit and healthy individuals to undergo surgical reconstruction in order to improve their quality of life and minimise the risk of future knee degeneration.

The surgical treatment of ACL injuries is a prolonged process beginning with reconstructive surgery, followed by a 9 to 12-month course of monitored rehabilitation.

ACL reconstruction surgery is usually performed through arthroscopy. The patient will be under general anaesthesia. The orthopaedic surgeon makes several small incisions at the knee and inserts a viewing instrument and other surgical instruments.

The torn ACL will then be replaced with a tissue graft, usually harvested from a tendon of the patient. The most common source of this tendon is the two hamstring tendons from the inner thigh. The benefits of arthroscopy is that it is a minimally invasive procedure, which can mean less pain and quicker recovery times. Patients can usually be discharged within 24 hours.

After surgery, the patient may be fitted with an ACL brace and taught to walk with crutches. Most patients will regain the ability to walk without crutches within 2 weeks. They will then embark on a 9-12 month course of monitored rehabilitation in stages.

Rehabilitation and recovery

The estimated time for a return to the patient’s sporting activity of choice is 9 months.

After the initial 2 weeks of recovery from surgery, the patient will begin with knee strengthening and range of motion exercises, which will take anywhere from 6 weeks to 3 months.

At the 3 month mark, most patients will be able to embark on a more rigorous course of physical therapy which might include squats and straight-line running. This stage of rehabilitation continues till the 9-month mark.

Typically, at 9 months most patients will be able to return to their sport of choice and may begin sport-specific rehabilitation.

If you are looking for orthopaedic treatments in Singapore, feel free to book an appointment at The Orthopaedic and Pain Practice today! Dr. Yong Ren will be happy to give you a consultation.

For assessment of your condition, please book an appointment with Dr Yong Ren.

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Sarah Taylor

Obstetrics & Gynaecology