The ‘Pop’ and the ‘Lock’: ACL vs. Meniscus Tears

A sudden knee injury during sport can be alarming, especially when it involves a painful “pop” with swelling or difficulty walking afterwards.

For many active Australians, one of the first questions after this type of injury is if they have torn their ACL or damaged their meniscus. Though both injuries can occur during similar sports movements and may feel alike at first, they are very different conditions that require careful assessment and management.

At Ortho ARC in Brisbane, our team regularly assess people with knee injuries that are sustained during netball, soccer, rugby, AFL, basketball, running and gym training. Understanding the difference between an ACL vs. Meniscus tear can help patients seek medical attention sooner and reduce the risk of further joint damage.

Why ACL and Meniscus Injuries Happen During Sport

The knee is a complex joint that relies on ligaments, cartilage, tendons, and muscles working together to provide stability and movement. Two structures that are commonly injured during sport are the anterior cruciate ligament (ACL) and the meniscus. Both injuries often occur during twisting or pivoting movements, especially when changing direction quickly or landing awkwardly.

What Is the ACL?

The ACL is one of the main stabilising ligaments of the knee. It helps control rotational movement and prevents excessive forward movement of the shin bone beneath the thigh bone.

Of all the countries in the world, Australia has the highest reported rate of anterior cruciate ligament (ACL) injuries, with the most common cause being sports injury.

What Is the Meniscus?

The meniscus is a crescent-shaped piece of cartilage that acts as a shock absorber, positioned between the thigh bone and shin bone. Each knee has two menisci, one on the inside and one on the outside of the joint, helping distribute load, absorb shock and support joint movement.

Meniscal tears may occur during twisting injuries or gradually over time due to cartilage wear and degeneration.

I Heard a “Pop…” What Does That Mean?

Patients with both ACL injuries and meniscal tears may describe hearing or feeling a “pop” at the time of injury.

This is why the injuries are commonly confused in the early stages. The symptoms that develop afterwards are usually more indicative as to which structure may be injured.

Signs That May Suggest an ACL Injury

ACL injuries commonly occur during non-contact twisting or pivoting movements, particularly in sports such as netball, soccer and basketball. Instances where sudden direction changes place high rotational stress on the knee.

Many people seen at Ortho ARC describe the knee feeling unstable or unreliable during movement after the initial injury. They often report experiencing:

  • A sudden popping sensation
  • Immediate pain
  • Rapid swelling within the first few hours
  • Difficulty continuing sport immediately afterwards
  • A feeling that the knee may “give way”
  • Instability when walking or turning
  • Pain with weight-bearing or changing direction

Rapid swelling after injury is one of the more common signs associated with ACL rupture, as bleeding may occur inside the joint following ligament damage.

In Brisbane, our orthopaedic specialists frequently see ACL injuries sustained during community sport competitions and training sessions around sporting hubs and local facilities. We also assess injuries through referrals connected with Greenslopes Private Hospital and surrounding sports medicine networks.

Signs That May Suggest a Meniscal Tear

Meniscal tears can occur during the same type of twisting movements that injure the ACL, but they can also develop gradually through wear and tear.

Meniscal tears often present with more localised symptoms, where patients may notice:

  • Pain along the inner or outer side of the knee
  • Tenderness at the joint line
  • Clicking or catching sensations
  • Difficulty fully bending or straightening the knee
  • Intermittent swelling
  • Mechanical locking or stiffness

One of the more distinctive symptoms of a meniscal tear is mechanical locking. Patients may describe the knee temporarily becoming stuck or unable to fully straighten.

Unlike ACL injuries, patients with meniscal tears may still continue activity or sport initially before symptoms become more noticeable or worsening over the following days.

Can ACL and Meniscus Injuries Happen Together?

Yes. ACL injuries and meniscal tears frequently occur together during sporting incidents involving forceful twisting or pivoting. This is one reason why orthopaedic assessment is important after a knee injury, even when symptoms appear manageable initially.

At Ortho ARC Brisbane, assessment includes discussion of the injury mechanism, symptom progression, knee stability and imaging findings to help determine the extent of joint injury and guide treatment planning.

Why Early Assessment Matters

Continuing to train or compete on an unstable knee may place additional stress on cartilage, ligaments and surrounding structures inside the joint.

Repeated episodes of instability or locking may increase the risk of further injury within the knee.

An accurate diagnosis is important because treatment recommendations differ depending on:

  • The injured structure
  • The severity of the injury
  • Sporting demands
  • Patient age and activity level
  • Knee stability
  • Associated cartilage damage

At Ortho ARC, treatment discussions may involve rehabilitation pathways, return-to-sport considerations, surgical planning and long-term knee health depending on the injury pattern.

Is MRI Needed for Diagnosis?

MRI scans are commonly used when ACL or meniscal injuries are suspected because they provide detailed imaging of the soft tissues within the knee.

An MRI may help confirm:

  • ACL rupture or partial tear
  • Meniscal tear location and severity
  • Cartilage injuries
  • Bone bruising
  • Other ligament damage

This imaging helps our orthopaedic surgeons at Ortho ARC to develop an individual treatment and rehabilitation plan.

ACL and Meniscus Treatment Options

Treatment depends on the injury, knee stability, activity and patient goals. There is no single treatment approach that suits every patient.

Treatment and management are influenced by:

  • Age
  • Sporting participation
  • Occupation
  • Degree of instability
  • Associated injuries
  • Lifestyle goals

ACL Injury Treatment

ACL injuries may be managed with physiotherapy, rehabilitation or ACL reconstruction surgery depending on instability symptoms and sporting requirements.

For some active individuals, particularly those participating in pivoting sports, ACL reconstruction may be recommended to improve knee stability.

Meniscus Tear Treatment

Treatment recommendations for meniscal injuries depend on the tear type, cartilage quality, knee stability and symptom severity. These may be treated with rehabilitation, repair techniques, arthroscopic surgery or partial meniscectomy in selected cases.

Ortho ARC’s philosophy on orthopaedic management is not only about symptom relief but on preserving long-term joint health wherever possible.

Supporting Recovery and Return to Sport

Recovery following a knee injury can take time. It usually involves a tailored physiotherapy program and progressive rehabilitation. Individual recovery can vary, but staying consistent in your structured plan assists your recovery and can help reduce the risk of re-injury.

Your physiotherapy program can support:

  • Strength
  • Knee movement
  • Balance and control
  • Range of motion
  • Technique
  • Return-to-sport readiness

When Should You Seek Medical Assessment?

It is important to seek professional medical assessment after a knee injury if you experience:

  • A popping sensation during sport
  • Rapid swelling of the knee
  • Knee instability or giving way
  • Difficulty weight-bearing
  • Mechanical locking or inability to straighten the knee
  • Persistent pain after twisting the knee

Early evaluation from an Orthopaedic Specialist may help identify ligament or cartilage injuries before further joint damage develops.

ACL and Meniscus Injury Assessment in Brisbane

Dr Blake Fidock and the team at Ortho ARC provide assessment and management of sports-related knee injuries across Brisbane, including ACL ruptures, meniscal tears and knee instability injuries.

Consultations include discussion of injury patterns, imaging, rehabilitation pathways, surgical considerations and return-to-sport planning tailored to the individual patient.

Patients experiencing swelling, instability, locking or ongoing knee pain after sport may benefit from orthopaedic assessment and MRI referral where required.

Book Your Knee Injury Consultation with Ortho ARC

Ask your GP for a referral to Ortho ARC Brisbane to discuss your knee symptoms and treatment options.

Already have a referral?

Book Your Consultation

References:

Anterior Cruciate Ligament Injury | Sports Medicine Australia. (2023). Sports Medicine Australia. https://sma.org.au/resources/injury-fact-sheets/acl-injury-2/

Practitioners, T. R. A. C. of general. (2012). Meniscal tear. Australian Family Physician. https://www.racgp.org.au/afp/2012/april/meniscal-tear

Olivia.Mowat. (2021, August 4). ACL Rehab. Allsports Physiotherapy & Sports Medicine. https://www.allsportsphysio.com.au/2021/08/acl-injuries-why-are-they-so-common-in-australia/

Australia, H. (2020, December 9). Knee injuries. Www.healthdirect.gov.au. https://www.healthdirect.gov.au/knee-injuries

Dr Blake Fidock (MED0001788650) MBBS (Hons. 1), MTrauma (Ortho), FRACS (Ortho), FAOrthA is a Specialist Orthopaedic Surgeon in Brisbane. This information is general in nature and is not a substitute for medical advice, diagnosis or treatment and does not establish a doctor-patient relationship. All surgery carries risk and individual results may vary. Please consult your GP regarding your individual circumstances and for referral if required.