Acute knee injuries, explained

The knee is a commonly injured part of the body. In fact, in sport it’s the most commonly injured part, with research finding that up to one in four of all sport injuries affect the knee. Read on to learn more.


What is a knee joint?

Your knee joint is made up of many different structures – ligaments, bones, joint cartilage and two menisci (which are also made of cartilage). These structures all work together to give you:

  • mobility, which lets your knee bend and straighten when you walk, run and jump
  • stability, which keeps all the structures safely connected together while you’re being active.

Ligaments, such as the ACL, have an important role in providing stability in the knee. The two menisci provide both mobility and stability, as well shock absorption in the joint.

Anatomy of the knee joint


What is my knee joint injury?

An acute injury of the knee joint is the result of a single incident – such as a twist, fall, excessive force or direct blow from a solid object. The knee cannot cope with the type of action that has occurred and this damages one or more structures, for example, tearing a meniscus or a ligament.

If you see a health professional, they will diagnose which structure in your knee joint has been injured and how badly it’s been damaged.

An accurate diagnosis will help your health professional to recommend the most effective and safest treatment.

However, making an accurate diagnosis can sometimes be a challenge. Injuries to different structures can cause similar symptoms such as pain, swelling, bruising and difficulty walking and running.

So how does your health professional make an accurate diagnosis? In most cases it is a combination of history and physical examination.

Taking your history

This involves your health professional asking you specific questions.

An important question is ‘how did the injury happen?’

For example, an ACL tear – the most common acute knee injury – may typically occur when you suddenly change direction. This can happen while running and performing cutting movements in sports such as football and basketball.

Conducting a physical examination

A health professional will combine physical tests with focussed questions about exactly how you injured your knee to inform the diagnosis.


This involves your health professional checking you for symptoms such as swelling, your joint movements and muscle strength, and your response to physical tests that assess your ligaments and menisci.

Do I need an X-ray?

In most cases, no.

X-rays can make an accurate diagnosis of a bone fracture (break). But only 7% of acute knee injuries are bone fractures.

So how does a health professional decide whether you need an X-ray?

In 1995, doctors in Ottawa, Canada, developed a set of rules, called the Ottawa Knee Rules, that can identify which people presenting with acute knee injuries are most likely to have a fracture.

These rules can help a health professional decide if you need an X-ray. These rules can also help you avoid having a dose of radiation due to an unnecessary X-ray.

If your health professional recommends an X-ray, asking the 5 questions recommended by Choosing Wisely Australia can help make sure you end up with the right amount of care – not too much and not too little.

Do I need an MRI?

In Australia, magnetic resonance imaging (MRI) can be used for an acute knee injury to help your health professional diagnose an anterior cruciate ligament (ACL) tear or meniscus (cartilage) tear.

However, research shows that a history and physical examination by an experienced health professional is as accurate as, if not better than, a knee MRI.

As a result, the Royal Australian College of General Practitioners recommends that an MRI is only needed when a diagnosis is still unclear after a history and physical examination AND if confirming diagnosis with an MRI will change your treatment.

Another reason for a limited role for knee MRIs is that they can have downsides. In particular, MRI can sometimes find a ‘problem’ that is not a real injury.

For example, a person of any age can have a meniscus tear that doesn’t cause pain or swelling and doesn’t require treatment.

But once this type of meniscus tear is ‘discovered’ on an MRI, it may cause anxiety and sometimes may lead people to have unnecessary and expensive treatments, even surgery.

Just as with an X-ray, if your health professional recommends an MRI, asking the 5 questions recommended by Choosing Wisely Australia can help make sure you end up with the right amount of care — not too much and not too little.

What can I do?

If your health professional has decided (following a history and physical examination) that your injury will settle with simple treatment such as rest and ice, you can manage your injury yourself under their supervision in the first few days.


  • Rest – avoid using the injured joint for at least 2 days.
  • Ice – apply ice packs for 20 minutes every 2 hours (never apply ice directly to skin – it can burn)
  • Compression – firmly bandage the injury.
  • Elevation – lie or sit with leg raised.


  • No Heat.
  • No Alcohol
  • No Running or similar activity
  • No Massage

Apart from providing these tips your health professional may also recommend using over-the-counter pain relief medicines.

When should I go back to see my health professional?

Your health professional may ask you to return in a few days once the swelling has gone down, so they can check your progress.

But you should go back to see your health professional as soon as possible if:

  • the pain, swelling or stiffness does not settle within a few days
  • the symptoms become worse despite following medical advice including RICE, no HARM and pain-relief medications
  • you develop a fever or redness at the injury site.

Should I have surgery?

Many acute knee injuries that don’t cause a bone fracture don’t need surgery. Research shows, for example, that an ACL tear can recover with the assistance of treatments such as RICE, no HARM and a rehabilitation program that includes specific exercises.

Deciding whether or not to have surgery involves weighing up different factors.

One important factor is how badly a structure is damaged. For example, if you have a swollen and painful knee due to a specific type of meniscus tear called a ‘bucket handle’ tear, surgery may be recommended because it is unlikely to heal properly on its own.

Another factor is how important it is for you to be active at a high level, such as playing competitive sport. If you’re keen to get back to competitive sport at a high level, you may decide, in consultation with your health professional and surgeon, to have reconstructive surgery, for example for an ACL tear.

How do I prevent another knee injury?

It may take weeks or months for you to recover and return to your normal level of activity. Recovery usually involves treatments such as strengthening, flexibility and functional exercises under the supervision of your health professional.

Specialised knee exercises can help restore knee strength and function. (Image:

For example, if you play sports that involve jumping, such as basketball, you would be advised to include jumping as a functional exercise.

Give yourself time to build up to your normal level of activity.

Warm up and cool down before and after activity such as sport, and give your knee joint time to recover between exercise sessions. Taping or bracing the joint under the supervision of your health professional may also help.

If you are overweight, weight loss can reduce pressure on the knee joint and lowers the chance of further injury.

Where can I get more information?

Choosing Wisely Australia

Choosing Wisely Australia is an initiative that brings the community together to start important conversations amongst healthcare providers and consumers. These conversations aim to improve the quality of healthcare through considering tests, treatments, and procedures where evidence shows they provide no benefit or, in some cases, lead to harm. Facilitated by NPS MedicineWise, it is led by a large cross-section of colleges, societies and associations that have identified practices that warrant scrutiny, and by examining the evidence and drawing on the expert opinion of their members, have developed lists of recommendations. Three colleges and associations recommend that health professionals use the Ottawa Ankle Rules:

Better Health Channel

Fully funded by the Victorian Government, this website provides health and medical information that is quality-assured and reliable, up-to-date, locally relevant and easy to understand. The information about ankle sprains is general in nature.


Jointly funded by the Australian Federal Government and the governments of the Australian Capital Territory, New South Wales, Northern Territory, South Australia, Tasmania, and Western Australia, this website provides services including high quality information by acting as a portal to reliable and reputable sources. The information about ankle sprains is general in nature.


Produced by Australian and New Zealand radiologists and other health professionals about radiology tests and procedures. It contains information for health consumers and treating health professionals, endorsed by the Royal Australian and New Zealand College of Radiologists (RANZCR). It provides specific information about imaging tests for injuries of the musculoskeletal system (bones, ligaments, muscles and more).


Public information resource for patients developed by physicians from the Radiological Society of North America (RSNA) and the American College of Radiology (ACR). It provides specific information about imaging tests for injuries of the musculoskeletal system (bones, ligaments, muscles and more).