Anterior Cruciate Ligament (ACL) Injury

Injured knee is throbbing and tender when touched

What is anterior cruciate ligament (ACL) injury?

The anterior cruciate ligament (ACL) is one of the two cruciate ligaments found in the middle of the knee with the purpose of preventing the shin bone from sliding out of its position. The ACL is one of the ligaments connecting the tibia to the femur and it plays a crucial role in the maintenance of knee joint mechanics and kinematics — keeping the joints in place and allowing optimal movement of joints. This ligament specifically, prevents your knee from moving too far forwards. 

An ACL injury, thus, causes limitations in movement and interrupts your stability. An ACL injury is also a common injury that one can incur and is often accompanied by other forms of knee injuries such as meniscus injuries.  

anterior cruciate ligament (ACL)
Anterior cruciate ligament (ACL) is a ligament found between the tibia and femur.

ACL injury is commonly regarded as a “sprain” and can manifest as:

  • Partial tear: ligament becomes loose, however, these forms of tear are rare. 
  • Complete tear: ligament is torn or ruptured in half or completely pulled away from the bone.

The extent of the injury is graded by different levels of sprain:

  • Grade 1: mild damage in the form of a stretch but still capable of maintaining joint stability. 
  • Grade 2: ligament is loose, ability to maintain joint stability is affected, and often referred to as a partial tear. 
  • Grade 3: complete tear or rupture and knee joint is completely unstable.
ACL injury
ACL injuries are graded according to the severity of the tear or strain.

What causes anterior cruciate ligament (ACL) injury?

ACL injury is often caused by trauma to the knee or an improper movement that releases impact on the joint. 

These include:

  • A sudden change of direction that places strain on the ligament
  • Abruptly stopping when moving in a fast motion
  • Incorrectly landing causing an upward force on the ligament 
  • Direct and heavy contact at the knee 

What are the symptoms of anterior cruciate ligament (ACL) injury?

Some of the signs that you have an ACL injury include:

  • A loud “pop” or “snap” when an injury occurs 
  • Swollen knees
  • Pain that forces you to compensate by using the uninjured leg for support 
  • Difficulty conducting any form of movement (walking, running)
  • Generally feeling unstable and the sensation of your leg “giving away” or buckling
ACL injury football
Abrupt movement during sports activities is often the cause of ACL injuries.
If you notice any of the symptoms, make an appointment with an orthopaedic specialist to get an accurate diagnosis and treatment.

Dr Puah KL is our Senior Consultant Orthopaedic Surgeon at Artisan Sports & Orthopaedic Surgery. He used to serve the sports service of Singapore General Hospital - the highest volume trauma centre for orthopaedics in Singapore.

Is anterior cruciate ligament (ACL) injury painful?

Yes. After the initial jolting pain during injury, one may feel like their injured knee is throbbing and tender when touched.

Pain has been reported between mild and excruciating, the levels varying by the degree of sprain that one has incurred. Even amongst those with a high tolerance for pain, an ACL injury still provides high levels of discomfort. 

Who is at risk of anterior cruciate ligament (ACL) injury in Singapore?

A consistent risk pattern has been noted in ACL injuries which include:

  • Athletes: ACL injuries are common among athletes of football, rugby, and basketball. 
  • Gender: women athletes are more prone to ACL injuries potentially attributed to the anatomical difference of the lower extremities, looseness of ligaments, and other physical conditioning.

How is  anterior cruciate ligament (ACL) injury diagnosed?

ACL injuries are diagnosed in the following ways: 

  • Physical examination and medical history: inform your orthopaedist of the potential activities that may have led to an injury such as trauma, exercise, or sports. Physically the area of injury will be examined and several motion tests will be conducted to review the injury. 
  • Imaging tests: magnetic resonance imaging (MRI) or dynamic ultrasonography would be required to examine if surrounding areas of the ACL are impacted given the likelihood of ACL injury being accompanied by other forms of injury. An x-ray if a fracture is suspected.
  • Diagnostic arthroscopy: arthroscopy, a minimally invasive procedure would be conducted where a small camera is inserted into the knee joint to visualise the structures inside if a diagnosis cannot be made from other tests or if surrounding damage of the knee is predicted.
MRI knee
MRIs are used in the diagnosis of ACL injuries.

What are the treatment options for anterior cruciate ligament (ACL) injury in Singapore?

Depending on the severity and individual need ACL injuries can be treated by:

  • Rest: you would be advised to observe complete rest to relieve pain and reduce swelling.
  • Medications: non-steroidal anti-inflammatory drugs (NSAIDs) and painkillers are commonly prescribed as the first course of treatment to reduce inflammation and manage pain.  
  • Injections: corticosteroid injections may be administered to reduce inflammation and provide immediate relief. 
  • Brace: to reduce movement of the joint and allow the ligament to heal.
  • Crutches: to limit placing weight on the affected knee.
  • Physiotherapy: upon discontinuation of the use of the brace, an active range of motion exercise would be administered via physiotherapy to regain mobility and strengthen muscle.
  • Surgery: knee arthroscopy surgery would be administered if deemed necessary to restore the structure of ligament damage. 
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Feeling aches and pains?

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For emergency appointment, please call or Whatsapp us at (65) 8909 8877. We will arrange for a limousine to send you to our clinic.
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