Anterior Cruciate Ligament (ACL) Injury

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

An Anterior Cruciate Ligament (ACL) injury involves a tear or sprain of the ACL, one of the key ligaments that help stabilise the knee joint. ACL injuries are common in sports that involve sudden stops, changes in direction, or jumping, such as football, basketball, and skiing.

Aetiology

ACL injuries typically occur due to:

• Sudden deceleration or change in direction while running
• Landing awkwardly from a jump
• Direct impact to the knee, such as in a tackle
• Twisting or pivoting on a planted foot

Pathophysiology

The pathophysiology of ACL injury involves:

• Overstretching or tearing of the ACL due to excessive strain
• Partial or complete rupture of the ligament, leading to instability of the knee
• Associated injuries, such as meniscal tears, cartilage damage, or injury to other ligaments
• Inflammation and haemorrhage within the joint

Risk Factors

• Participation in high-risk sports, such as football, basketball, or skiing
• Female gender, due to anatomical and hormonal differences
• Previous ACL injury
• Poor neuromuscular control and muscle imbalances
• Inadequate warm-up or stretching before physical activity
• Improper footwear or playing surfaces

Signs and Symptoms

The signs and symptoms of ACL injury include:

• A loud "pop" or "crack" sound at the time of injury
• Severe pain and inability to continue activity
• Rapid swelling of the knee
• Instability or "giving way" of the knee, especially during weight-bearing activities
• Limited range of motion due to pain and swelling

Investigations

Specific investigations to diagnose an ACL injury include:

• Clinical examination: Physical tests such as the Lachman test, anterior drawer test, and pivot shift test to assess knee stability.
• Imaging studies:
  • MRI: The gold standard for diagnosing ACL tears, assessing the extent of the injury, and detecting associated injuries.
  • X-rays: To rule out fractures or other bone injuries.
  • Ultrasound: May be used to assess ligament and soft tissue injuries.

Management

Primary Care Management

• Initial assessment and referral: Prompt referral to orthopaedics or sports medicine for further evaluation and management.
• RICE protocol: Rest, Ice, Compression, and Elevation to reduce swelling and pain.
• Pain management: Analgesics such as paracetamol or NSAIDs to relieve pain and inflammation.
• Immobilisation: Use of a knee brace or crutches to stabilise the knee and prevent further injury.

Specialist Management

• Non-surgical management:
  • Physiotherapy: Focused on strengthening the muscles around the knee, improving range of motion, and restoring function.
  • Activity modification: Avoiding high-risk activities that may exacerbate the injury.
• Surgical intervention:
  • ACL reconstruction: Surgical repair of the torn ligament using grafts from the patient (autograft) or a donor (allograft).
  • Postoperative rehabilitation: Intensive physiotherapy to restore knee stability, strength, and function after surgery.

References

1. NHS (2024) Anterior Cruciate Ligament (ACL) Injury. Available at: https://www.nhs.uk/conditions/acl-injury/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Knee Injuries: Anterior Cruciate Ligament. Available at: https://cks.nice.org.uk/topics/knee-injuries-anterior-cruciate-ligament/ (Accessed: 24 June 2024).
3. British Medical Journal (2024) ACL Injuries: clinical features, diagnosis, and management. Available at: https://www.bmj.com/content/350/bmj.h2409 (Accessed: 24 June 2024).
4. American Academy of Orthopaedic Surgeons (2024) Anterior Cruciate Ligament (ACL) Injuries. Available at: https://orthoinfo.aaos.org/en/diseases--conditions/anterior-cruciate-ligament-acl-injuries/ (Accessed: 24 June 2024).

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