ACL (Anterior Cruciate Ligament) Tears

The anterior cruciate ligament, or ACL, is one of the key ligaments that help stabilise the knee joint. An ACL tear is a common injury, particularly among athletes who engage in sports that involve sudden stops, jumps, or changes in direction. This type of injury can range from a small sprain to a total tear, affecting mobility and quality of life. When the ACL is torn, people often experience pain, swelling, and a feeling of instability in the knee, making it difficult to walk or stand.

Experiencing persistent knee pain or suffered a sports injury recently? Consult our ACL specialist for an accurate diagnosis & personalised treatment plan.

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Dr Dennis Ng Zhaowen

Causes of ACL Tears

ACL tears occur when the anterior cruciate ligament in the knee is overstretched or torn. Several factors can contribute to this type of injury, including:

  • Knee Twist in Sports - Sports that involve sudden stops or rapid changes in direction, such as basketball, soccer, and football, can put excessive stress on the ACL. When the knee twists or pivots suddenly, the ligament can tear, affecting the knee's function and daily activities.
  • Falls or Improper Landing - People who frequently jump, such as in volleyball or gymnastics, and land awkwardly can tear their ACL. An improper landing can exert enough force to tear the ligament.
  • Physical Trauma - A direct blow to the knee, common in contact sports like football or hockey, can result in an ACL tear. This type of trauma often occurs during tackles or collisions with other players.
  • Overextension of the Knee - Straightening the knee joint too forcefully, such as during certain athletic activities, can cause the ACL to tear. This is sometimes seen in sports like skiing, where the lower leg is suddenly pulled forward.
  • Poor Conditioning and Fatigue - Weak muscles around the knee, especially the quadriceps and hamstrings, can increase the risk of an ACL tear. Fatigue can also play a role, as tired muscles cannot effectively support and stabilise the knee joint.

Symptoms of an ACL Tear

Recognising the symptoms of an ACL tear is important for early diagnosis and treatment. The following signs are commonly associated with an ACL injury:

  • Severe Pain
    Those who experience an ACL tear often report sudden and severe pain in the knee at the time of injury. This pain is typically intense and can make it difficult to continue physical activity.
  • Popping Sensation
    A noticeable “pop” sound or sensation in the knee at the moment of injury is a typical sign of an ACL tear. Many people describe feeling or hearing this pop when the ligament tears.
  • Swelling and Bruising
    Swelling around the knee typically develops within a few hours after the injury. This swelling results from bleeding within the joint, which causes the knee to become puffy and tender. A few days after the injury, bruising may also appear around the knee due to internal bleeding.
  • Instability
    A torn ACL often leads to a feeling of instability or the knee “giving way.” This can make it difficult to bear weight on the affected leg and cause the knee to buckle unexpectedly during physical activities.
  • Limited Movement
    Following an ACL tear, people may experience a reduced range of motion in the knee. This stiffness can prevent the knee from fully bending or straightening, limiting normal movement.

Diagnosis of ACL Tears

Accurate diagnosis of an ACL tear is important for determining the appropriate treatment plan. The diagnostic process typically involves the following steps:

Medical History

The first step in diagnosing an ACL tear is taking a detailed medical history. The knee specialist will ask about how the injury occurred, the symptoms experienced, and any previous knee injuries. This information helps the knee specialist understand the context of the injury and its severity.

Physical Examination

A physical examination of the knee is conducted to assess the extent of the injury. The knee specialist will look for signs such as swelling, bruising, and tenderness. Specific tests, such as the Lachman test and the anterior drawer test, are performed to check the stability of the ACL. These tests involve moving the knee in certain ways to see if abnormal movement indicates a tear.

Imaging Tests

To confirm the diagnosis and determine the severity of the ACL tear, imaging tests are often required:

  • X-rays: X-rays are used to rule out any bone fractures that might have occurred along with the ACL injury. Although X-rays do not show soft tissues like ligaments, they are useful for detecting bone-related issues.
  • MRI (Magnetic Resonance Imaging): An MRI is the most definitive imaging test for diagnosing an ACL tear. It provides detailed images of the knee’s soft tissues, including the ligaments, tendons, and cartilage. An MRI can reveal the extent of the ACL tear and any other injuries, like meniscus or other ligament damage.

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Treatment Options

ACL tears are treated based on severity and activity level. Treatment minimises discomfort and swelling, restores knee function, and avoids damage. Non-surgical and surgical treatments are available.

Non-Surgical Treatments

Non-surgical treatments may be sufficient for less severe ACL tears or people who are not highly active. These treatments focus on:

RICE Method

The RICE method is a standard initial treatment for ACL injuries. It includes Rest, Ice, Compression, and Elevation, each important in managing pain and swelling.

  • Rest: Rest is recommended to prevent further injury and to initiate healing. Avoiding activities that put additional stress on the knee helps minimise further damage to the ligament.
  • Ice: Applying ice to the knee reduces pain and swelling. Ice should be applied for 20 minutes every two hours during the first 48 hours after the injury. This helps constrict blood vessels and reduce internal bleeding and swelling.
  • Compression: An elastic bandage or compression wrap can help control swelling and support the knee. Compression aids in reducing swelling by preventing the accumulation of fluids in the knee joint.
  • Elevation: Keeping the knee elevated above the heart level helps decrease swelling by allowing fluids to drain away from the injured area. Elevation is most effective when combined with rest and ice.
Physical Therapy

Physical therapy is an important part of healing that does not involve surgery. As part of an organised rehabilitation programme, knee exercises are used to make the knee stronger, more flexible, and more stable. The knee specialist shows patients specific exercises that build the muscles around the knee, especially the quadriceps and hamstrings, which help keep the knee stable.

Wearing a Knee Brace

A knee brace can give your knee extra support and stability, especially during physical activities. Braces help keep the knee from getting hurt again and let people slowly return to normal activities.


Over-the-counter pain relievers and anti-inflammatory medications can help manage pain and reduce swelling. Sometimes, the knee specialist may prescribe stronger medications to control pain.

Corticosteroids for ACL Tears

Corticosteroid injections are used to reduce inflammation and pain from ACL (Anterior Cruciate Ligament) tears. These injections provide immediate relief by decreasing swelling and discomfort, making it easier for patients to engage in physical therapy. However, corticosteroids do not promote tissue healing and are best used as part of a broader treatment plan.

Hyaluronic Acid for ACL Tears

Hyaluronic acid injections help manage ACL tear symptoms by lubricating and cushioning the knee joint. This treatment improves mobility and reduces pain, especially if the ACL tear is accompanied by osteoarthritis. While it doesn’t heal the torn ligament, it enhances joint function and comfort.

Platelet-Rich Plasma (PRP) for ACL Tears

Platelet-rich plasma (PRP) therapy involves injecting concentrated platelets from the patient’s blood into the injured ACL. This stimulates tissue repair and regeneration, promoting healing and reducing pain and inflammation. PRP supports the restoration of ligament strength and function, offering a promising alternative to surgery.

Surgical Treatments

For more severe ACL tears, particularly in active people or athletes, surgery may be recommended. Surgical treatment involves reconstructing the torn ligament using a tissue graft.

ACL Reconstruction

ACL reconstruction is the most common surgical procedure for treating ACL tears. This surgery involves replacing the torn ligament with a graft, which can be sourced from the patient’s own body (autograft) or from a donor (allograft). Common autograft sources include the patellar tendon, hamstring tendon, or quadriceps tendon. The surgeon secures the graft in place using screws or other fixation devices, allowing the new ligament to integrate and stabilize the knee over time.

ACL Repair

In certain cases, particularly with partial tears or tears near the ligament’s attachment to the bone, ACL repair may be a viable option. This procedure involves suturing the torn ligament back together. ACL repair is less common than reconstruction and is typically considered for specific patient populations, such as younger individuals or those with specific tear patterns.

Augmented ACL Reconstruction

Augmented ACL reconstruction combines traditional reconstruction techniques with additional supportive measures. One such method is the use of a synthetic scaffold to support the healing process and improve the integration of the graft. This approach aims to enhance the strength and stability of the repaired ligament, potentially leading to better long-term outcomes.


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Rehabilitation and Recovery

ACL tears require rehabilitation and healing, whether non-surgical or surgical. A structured rehabilitation program is needed to restore knee function, strength, and stability.

Non-Surgical Rehabilitation

Non-surgical rehabilitation involves strength and flexibility exercises to stabilise the joint. This includes:

  • Strengthening and Flexibility Exercises: These exercises target the quadriceps, hamstrings, and calf muscles to improve muscle support and maintain knee flexibility, which include leg presses, squats, and lunges. Flexibility exercises stretch knee muscles to maintain and improve range of motion. Hamstring and quadriceps stretches are the most common flexibility exercises.
  • Balance and Proprioception Training: Balance and proprioception exercises improve the body’s ability to sense the position of the knee joint, preventing further injuries. These exercises often involve balance boards or stability balls. These activities train the neuromuscular system to adapt to posture changes.
  • Functional Training: Functional training aims to restore the knee’s ability to handle real-life physical demands. It includes exercises such as step-ups, lateral movements, and agility drills.
Post-Surgical Rehabilitation

After ACL surgery, rehabilitation follows a planned routine to ensure healing and function. The post-surgical rehabilitation process generally includes several phases:

Initial Phase

In the initial phase, the focus is on reducing pain and swelling while gradually increasing the knee’s range of motion. Gentle exercises, such as heel slides and quad sets, are introduced to maintain muscle activity without straining the knee.

Intermediate Phase

As healing progresses, the rehabilitation program introduces more intensive strengthening and flexibility exercises. The goal is to restore the full range of motion and build muscle strength around the knee. Activities such as stationary biking and swimming may be incorporated.

Functional Phase

The functional phase emphasises regaining full function and preparing for a return to sports or daily activities. This includes more dynamic exercises like running, jumping, and agility drills. Patients also engage in sport-specific training tailored to their activity level.

Final Phase

The final phase focuses on a gradual return to pre-injury activities. The knee specialist assesses the knee’s strength, stability, and function to determine readiness for a safe return to sports or demanding physical activities.

Prevention of ACL Tears

Preventing ACL tears is important, especially for athletes and those engaged in high-risk activities. Preventive methods can greatly reduce injury risk. This includes:

  • Warm-Up and Cool-Down
    Incorporating proper warm-up and cool-down routines into workouts helps prepare the muscles and joints for physical activity. Warm-ups should include dynamic stretches and light aerobic exercises to increase blood flow, while cool-downs should focus on static stretching to improve flexibility and reduce muscle stiffness.
  • Use of Proper Technique
    Proper techniques during physical activities are key to lowering the risk of ACL tears. This includes correct landing mechanics when jumping, avoiding excessive inward movement of the knee during activities, and using appropriate form during exercises. Coaches and trainers should emphasise the importance of technique to athletes.
  • Wearing Suitable Footwear and Bracing
    Sports-specific footwear can improve support and traction, minimising the risk of ACL injuries from slips and falls. Proper footwear helps in preserving stability and alignment during exercise. In high-risk activities, a knee brace may support and stabilise the knee. Braces can avoid knee strain and injury for people with a history of ACL rupture.
  • Engage in Regular Exercise
    Regular exercise helps maintain overall fitness and muscle strength, supporting joint health and reducing the risk of injuries, including ACL tears. Consistent physical activity ensures that the muscles around the knee are strong and flexible, providing better support and stability.

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Learn what our patients have to say about our treatments and services.

Jeremy Teo
Jeremy Teo
I tore my left pec muscle after a bench press accident and had the fortune of getting help from Dr Dennis. He is a very caring and helpful individual that you can tell wants the best healing progress for you and actively follows up with you sincerely. I initially had a two month delay and misdiagnosis at Ktph and it caused my tendon to retract. Should have went to Dr Dennis from the start.. 5/5
Emily Loo
Emily Loo
I felt that doctor Dennis is very experienced and he skilfully aligned my fractured toe after my accident so that I didn’t need to do a minor surgery. He was friendly and professional and I felt his fees were reasonable without additional overselling of tests, supplements etc. that I have experienced elsewhere. Overall it was a smooth and effective experience and I would highly recommend doctor Dennis.
Ming W
Ming W
Wonderful experience with Dr. Dennis and his team. The staff were attentive and efficient. Dr. Dennis is professional, caring and knowledgeable. I had a shoulder injury and knee injury that required surgery. The whole journey, including pre and post surgery, Dr. Dennis and his team made sure I received the best treatment possible. Really thankful for the team and I definitely will recommend this place to others.
Jermy Tan
Jermy Tan
Saw Dr Dennis for my lumbar slipped disc. Great doctor and he explained clearly the different options available. Went with surgery and have been recovering well since then.
Amanda Seah
Amanda Seah
I came in with a shoulder injury that meds from a GP did not relieve one month ago. Dr Dennis and his team were great in diagnosing the exact injury with an mri, and he prescribed physio. My shoulder condition has greatly improved and I can now move my arm almost completely! Thank you Dr Dennis!
Jaslyn HENG (Kenrick)
Jaslyn HENG (Kenrick)
A very friendly and nice doctor who manage to cure my elbow issue whjch has been bothering me for more than 6 months! Thank you Doctor Dennis!
Xianmin Jiang
Xianmin Jiang
I had severe left shoulder pain due to exercise. After MRI checking , it was shown high-grade tendon tearing. Dr Dennis did the surgery for my left should calf repair. After surgery, I strictly follow what he suggested. The recovery was really amazing and fast. I was curious about what happened to my shoulder, he explained in details and with great patience. Now, I am fully recovered in a very fast speed and come back to my loved sports and exercises. I definitely recommend Dr Dennis for his profession, patience and delicate skills. Last not the least, thank for his medical team. The nurses are always prompt to reply when I need help and message them.
Omar Lechuga
Omar Lechuga
Dr. Dennis helped me with an elbow pinch coming from a trauma. His attention to detail confidence and great empathy really helped me to fully recover. Thank you Dr. Dennis.
Benjamin Mah
Benjamin Mah
Dr Dennis has been helpful in the diagnosis and explanation of my injury

Dr Dennis Ng Zhaowen
Mount Elizabeth Novena Specialist Centre
38 Irrawaddy Road #08-41,Singapore 329563

Dr Dennis Ng Zhaowen

  • Senior Consultant Orthopaedic Specialist
MBBS (Singapore)
FRCSEdOrth (Gold Medal Award)

Before private practice, Dr Dennis Ng was the former Deputy Head of the Shoulder & Elbow Division and Sports Knee Division in National University Hospital.

He completed his fellowship at the prestigious Fowler Kennedy Sports Medicine Centre in London, Ontario, Canada, and has rich experience treating professional athletes and returning them to sports. 

Special areas of interests include keyhole and reconstructive procedures of the knee and ankle. 

Common procedures include ACL Reconstruction, Meniscus repair, Cartilage resurfacing, Knee preservation etc.


Our clinic is on the specialist panels of the following Health Networks/Insurance Plans, and we are happy to assist with your claims or
attend to any query you may have.

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    Visit Us Today

    Mount Elizabeth Novena Specialist Centre

    38 Irrawaddy Road #08-41
    Singapore 329563

    Monday – Friday: 9am – 1pm; 2pm – 5pm
    Saturday: 9am – 1pm
    Sunday & PH: CLOSED

    Other Clinic Location

    Gleneagles Medical Center

    6 Napier Road #07-15
    Singapore 258499

    Monday – Friday: 9am – 1pm; 2pm – 5pm
    Saturday: 9am – 1pm
    Sunday & PH: CLOSED

    Frequently Asked Questions (FAQs)

    How long does recovery from an ACL tear take?

    Recovery time varies depending on the severity of the injury and the chosen treatment approach. Non-surgical recovery may take a few weeks to several months, while post-surgical recovery typically requires six to nine months of rehabilitation.

    Do all ACL tears require surgery?

    Not all ACL tears require surgery. The decision depends on the severity of the tear, the patient’s activity level, and overall health. Non-surgical treatments, including physical therapy, may be sufficient for less active people or partial tears.

    Will I be able to return to sports after an ACL tear?

    Many people return to sports after an ACL tear, especially with proper treatment and rehabilitation. The timeline for returning to sports varies, and it’s important to follow the knee specialist’s guidance to prevent re-injury.

    How soon should I see a knee specialist after a suspected ACL tear?

    It is advisable to see a knee specialist as soon as possible after suspecting an ACL tear. Early medical evaluation helps accurately diagnose the injury and initiate appropriate treatment to prevent further damage.

    What are the risks of not treating an ACL tear?

    Untreated ACL tears can lead to chronic knee instability, which may cause further damage to the knee joint, including meniscus tears and cartilage damage. Proper diagnosis and treatment are required to prevent long-term complications.

    +65 9751 1486