Knee Ligament Injuries and Instability

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Dr Kau Chung Yuan (许医生)


MRCS (Ireland)

MMed (Ortho)

FRCSEd (Ortho)


Introduction to Knee Ligament Injuries and Instability

Ligament injuries can range from mild sprains to complete tears, leading to varying degrees of instability in the knee.

The knee joint, being one of the body’s most complex and heavily used joints, is stabilized and supported by a network of ligaments. Injuries and instability not only impact the individual’s ability to perform daily activities but also increase the risk of further joint damage.

Types of Knee Ligament Injuries

Knee ligament injuries are classified based on the specific ligament affected and the severity of the injury. The main ligaments involved in knee stability are:

Anterior Cruciate Ligament (ACL) Injuries

The ACL stabilizes the knee during rotational movements. Injuries range from partial to complete tears, often occurring during sports that involve sudden stops or changes in direction.

Posterior Cruciate Ligament (PCL) Injuries

PCL injuries are less common and typically result from a direct impact to the front of the knee, such as during a car accident or a fall onto a bent knee.

Medial Collateral Ligament (MCL) Injuries

Injuries to the MCL are often caused by a blow to the outer side of the knee, leading to sprains that can range from mild (grade I) to severe (grade III).

Lateral Collateral Ligament (LCL) Injuries

The LCL helps stabilize the knee against forces that push the knee inward. Like MCL injuries, LCL injuries can occur due to direct impact or excessive pressure on the knee but are less common.

Multi-Ligament Injuries

In severe cases, multiple ligaments can be injured simultaneously, often resulting from significant trauma. These injuries are complex and pose a greater challenge for treatment and rehabilitation.

Causes of Knee Ligament Injuries and Instability

Understanding these diverse causes is crucial for prevention, effective treatment, and rehabilitation strategies.

  • Sports-Related Activities
    Many ligament injuries occur during sports that involve sudden stops, jumps, or changes in direction, such as soccer, basketball, football, and skiing. The dynamic and high-impact nature of these sports can place excessive stress on the knee ligaments.
  • Direct Impact
    Falls, motor vehicle accidents, or collisions can forcefully bend or twist the knee, leading to ligament damage.
  • Overuse and Repetitive Stress
    Repetitive activities that put continuous stress on the knee ligaments, such as long-distance running or cycling, can lead to overuse injuries over time, weakening the ligaments and increasing the risk of tears.
  • Previous Knee Injuries
    Individuals who have suffered previous knee injuries are at a higher risk of subsequent ligament damage due to weakened structures or compensatory movement patterns that place additional stress on the ligaments.
  • Congenital Weakness
    Some individuals may have inherently weaker ligaments or anatomical variations that predispose them to knee instability and increased risk of injury.


The symptoms of knee ligament injuries can vary depending on the specific ligament affected and the severity of the injury. Common symptoms include:

  • Pain and Tenderness
    Immediate pain at the time of injury, often severe if the ligament is torn. The pain is usually localized to the area around the injured ligament but can spread throughout the knee joint in more severe cases.
  • Bruising
    Bruising around the knee may appear a few days after the injury, indicating underlying tissue damage.
  • Swelling and Stiffness
    Swelling typically occurs rapidly after the injury, within hours, and can be a sign of a severe ligament tear or associated damage to other parts of the knee. The knee may also feel stiff, especially after periods of inactivity, as swelling and pain limit movement.
  • Reduced Range of Motion
    Difficulty bending or straightening the knee fully, often due to pain, swelling, or mechanical blockage caused by the injury.
  • Audible Popping or Snapping Sound
    Some ligament injuries, particularly ACL tears, are accompanied by a loud pop or snap at the time of injury.

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Diagnosing knee ligament injuries involves a comprehensive approach, following procedures such as:

Clinical Evaluation
  • Medical History: Inquiries about how the injury occurred, the symptoms experienced, and any previous knee injuries.
  • Physical Examination: Examine the knee for signs of swelling, tenderness, and bruising, and assess the range of motion. Specific tests, such as the Lachman test for ACL injuries or the valgus stress test for MCL injuries, may be performed to evaluate ligament stability.
Imaging Studies
  • X-rays: While X-rays cannot show ligament damage directly, they can rule out associated bone fractures and assess the overall alignment of the knee joint.
  • Magnetic Resonance Imaging (MRI): MRI provides detailed images of both complete and partial ligament tears and can also identify injuries to other knee structures, such as the menisci and cartilage.

In certain cases where the diagnosis remains unclear or to assess the extent of damage more accurately, arthroscopic surgery may be considered. This minimally invasive procedure involves inserting a small camera into the knee joint, allowing the surgeon to directly visualize the ligaments and other internal structures.

Non-Surgical Treatment Options for Knee Ligament Injuries

Non-surgical treatment options focus on alleviating symptoms and promoting healing without surgery. Common options include:

Rest and Immobilization

Initial rest is crucial to reduce swelling and pain. The use of crutches or a knee brace may be advised to avoid putting weight on the injured knee and prevent further injury while the ligament heals.

Ice and Compression

Applying ice to the knee for 20-30 minutes several times a day during the first few days after the injury can help reduce swelling. Compression bandages or wraps can also help minimize swelling and provide support to the injured knee.

Physical Therapy

Physical therapy focuses on exercises that strengthen the muscles around the knee, improve flexibility, and increase the range of motion.

Activity Modification

Avoiding activities that put stress on the injured ligament is important until the knee has healed sufficiently.

Surgical Treatment Options for Knee Ligament Injuries

Surgical treatment options are aimed at repairing or reconstructing the damaged ligaments to restore knee function. These include:

  • Ligament Repair
    Direct repair of the torn ligament may be possible in certain cases, particularly if the ligament has been avulsed (torn away) from the bone.
  • Multiligament Reconstruction
    In cases where multiple ligaments are injured, a more complex surgical approach may be required to restore the stability and function of the knee.
  • Ligament Reconstruction
    Reconstruction is often the preferred method for treating complete tears of the ACL and is also used for significant injuries to the PCL, MCL, and LCL. A graft is harvested from the patient’s own body (autograft) or a donor (allograft) and the new ligament is then anchored in place to recreate the original ligament’s function.

Dr. Kau Chung Yuan

MBBS (S’pore)

MRCS (Ireland)

MMed (Ortho)

FRCSEd (Ortho)

Dr Kau (许医生) is a Fellowship trained Orthopaedic Surgeon with a subspecialty interest in Hip and Knee surgery and has been in practice for more than 15 years.

He is experienced in trauma and fracture management, sports injuries, and joint replacement surgery.

  • Fellow of the Royal College of Surgeons Edinburgh, Orthopaedics (FRCS, Edin) 2014
  • Master of Medicine (Orthopaedics), Singapore (MMed) 2013
  • Member of the Royal College of Surgeons Ireland (MRCS, Ire) 2009
  • Bachelor of Medicine and Surgery (MBBS, Singapore) 2004

Preventative Measures for Knee Ligament Health

Preventative measures concentrate on strategies to strengthen and protect the knee, reducing the likelihood of ligament injuries.

  • Strength and Flexibility Exercises: Focusing on exercises that strengthen and maintain flexibility in the muscles around the knee, particularly the quadriceps and hamstrings, can help support the joint and reduce the tightness of its ligaments.
  • Proper Technique: Learning and applying the correct techniques for sports and physical activities, especially those that involve jumping, pivoting, and cutting motions, can help minimize stress on the knee ligaments.
  • Use of Appropriate Equipment: Wearing proper footwear that provides adequate support and cushioning can reduce the risk of knee ligament injuries, especially in activities that involve significant impact or lateral movements.
  • Warm-Up and Cool-Down: Engaging in a thorough warm-up before activity prepares the muscles and ligaments for the stresses to come, while a cool-down helps to gradually reduce heart rate and prevent stiffness.
  • Neuromuscular Training: Exercises that improve balance, coordination, and proprioception (the sense of joint position) can enhance knee stability and reduce the risk of ligament injuries.

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Patient Feedback

Ethan Chan
Dr. Kau is an exemplary doctor who is experienced in his field and is very patient with his patients. He walked me through the details of my knee condition and addressed all my concerns. Thanks to Dr. Kau, I had a better understanding of my ACL and MCL injury and the various treatment options available. His advice and treatment have been very valuable to me.
Ming Lee Chua
Dr Kau was very careful and explained clearly the surgery procedures. After surgery, the care while I was in hospital was closely monitored and he even came during weekends! The hip so far has recovered and healed. His ‘predictions’ of when what can happen are so accurate. Trust him.
Teo Pek Suan Diana
I had a very successful total hip replacement done by Dr Kau 4 years ago. 4 months after the operation I was back walking, cycling and swimming. The beautiful job gave me much confidence Dr Kau is most professional and has such great doctor patient communication.

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    Frequently Asked Questions (FAQs)

    Can knee ligament injuries heal on their own?

    Mild to moderate ligament injuries (sprains) can often heal on their own with appropriate care, including rest, ice, compression, and elevation (RICE protocol), along with physical therapy. However, complete tears may require more intensive treatment, including surgery.

    How does body weight impact knee ligament health and the risk of injury?

    Excess body weight increases the stress on knee ligaments during everyday activities and physical exercise, potentially leading to higher rates of wear and tear and a greater risk of injuries. Maintaining a healthy weight can reduce this risk and decrease the overall strain on the knee.

    Are there any long-term limitations after knee ligament reconstruction?

    Some individuals may experience long-term limitations after knee ligament reconstruction, such as reduced range of motion, lingering pain, or a need to modify certain activities to protect the knee.

    How do knee ligament injuries differ between children and adults?

    Children and adolescents may experience ligament injuries differently due to growth plate involvement, which can complicate diagnosis and treatment. Their recovery protocols often require adjustments to accommodate ongoing growth and development.