Knee Anatomy

Knee injuries are common, especially when taking part in sport. Injuries to soft tissues, such as ligaments and tendons, are the most common, though damage to the bones is also possible.

About knee injuries

The most common knee injuries are:

  • a sprain – one or more ligaments is overstretched through twisting or pulling; the ligament may be torn or ruptured
  • a strain – a tendon or muscle is overstretched
  • damage to the cartilage in your knee – the cartilage is a crescent-shaped disc called a meniscus, that acts as a ‘shock absorber’ in your knee
  • overuse – this is most common in people who run

Knee ligament injuries

Ligaments connect one bone to another. The ligaments outside your knee joint are called the medial collateral ligament and the lateral collateral ligament. They provide your knee with stability and limit the amount it can move from side to side.

Knee Anatomy

  • The medial collateral ligament is on the inner side of your knee and is taut when your leg is straight. It’s a strong ligament but can be sprained or completely ruptured (torn) if you twist your straightened leg at the same time as being knocked sideways, for example, when being tackled in rugby.
  • The lateral collateral ligament is like a thin, strong cord that runs on the outer side of your knee connecting the bottom of your thigh bone to the top of your fibula (one of the bones in your lower leg). It’s not usually damaged on its own, but you may need to have it repaired if you have damaged other ligaments.

Medial and lateral collateral ligament injuries may be classed as follows:

  • grade 1 is a sprain with no tearing of the ligament
  • grade 2 is a partial tear of the ligament
  • grade 3 is a complete tear of the ligament

The ligaments inside your knee joint are called the anterior cruciate ligament and the posterior cruciate ligament. Cruciate means in the form of a cross – the anterior cruciate ligament crosses over in front of the posterior cruciate ligament. These ligaments provide stability to your knee, when it is in different positions, particularly in the forward and backward movements of the knee joint.

Other soft tissue injuries

The other soft tissues around your knee can also be injured. Soft tissue means any tissue in your body that isn’t bone.

If you play a sport that involves twisting your upper leg while your foot is planted on the floor, you may tear the cartilage in your knee. The cartilage becomes worn down (degenerates) as you get older, making it easier to tear even after a very minor injury.

Overuse of your knee can also result in tearing a patellar tendon. Your patellar tendon connects your kneecap (patella) to your thigh muscle.

Symptoms of knee injuries

The symptoms for most ligament injuries will be similar, no matter which one has been damaged. These may include:

  • pain
  • swelling
  • instability – you may feel like your knee is giving way or that it’s locking

You may feel a popping or snapping sensation at the time of the injury, or even hear a popping sound. You may also find that you can’t stand properly on the affected leg, or put your full weight on it.

You won’t feel any direct pain if you injure the cartilage in your knee, but you may have some pain or discomfort from the swelling that follows an injury. Pain may develop on either the inside or outside of your knee joint (depending on which knee you have damaged the cartilage) and you may see some swelling.

If you have any of these symptoms, visit our doctor for advice.

Causes of knee injuries

You may injure your knee if:

  • it receives an impact or is moved beyond its usual range of movement, for example if you have a fall or land awkwardly
  • you play a sport that combines running, jumping and stopping with quick changes of direction, such as football
  • you have a condition such as osteoarthritis or gout, or are very overweight
  • your knees hit the dashboard in a car accident – posterior cruciate ligament damage is sometimes called the ‘dashboard injury’ as this is often how it occurs

Diagnosis of knee injuries

Dr. Kevin Yip will ask about your symptoms and examine you. This may include feeling for fluid in the joint by pressing gently over your kneecap, especially if your knee doesn’t look severely swollen. Our doctor will ask you to describe how the injury happened, where your pain is and what type of pain it is.

Our doctor may test for injury to your knee ligaments or soft tissues by bending and flexing your knee, and moving your leg into different positions, while you lie or sit down.

Our doctor may also ask you to perform movements such as stepping, squatting or hopping.

Our doctor may refer you for other tests in a hospital or clinic. These may include an MRI or ultrasound scan or occasionally X-ray. These tests can help to diagnose more complicated or severe injuries.

Treatment of knee injuries

The treatment you will receive will depend on what damage you have done and how bad the damage is.

Self help

You should follow the PRICE procedure to manage any type of soft tissue injury to your knee. PRICE stands for the following.

  • Protection. Protect your injury from further harm.
  • Rest. Rest the injury for the first two to three days, then reintroduce movement so you don’t lose too much muscle strength.
  • Ice. Apply a cold compress such as ice or a bag of frozen peas wrapped in a towel to help reduce swelling and bruising. Don’t apply ice directly to your skin as it can damage your skin.
  • Compression. Compress the joint by bandaging it to support the injury and help decrease swelling.
  • Elevation. Elevate your knee by resting it above the level of your heart and keep it supported.

There are certain things you should not do in the first three days after your injury to avoid doing further damage to your knee. These can be remembered as HARM.

  • Heat. This includes having a hot bath or using a heat pack.
  • Alcohol. Drinking alcohol can increase bleeding and swelling in the affected area.
  • Running or other forms of exercise.
  • Massaging the injured knee. This can cause more swelling or bleeding.

You may need to use crutches or wear a brace to make sure that you keep weight off the affected knee.


If your injury is more severe or complex, Our doctor may refer you to a physiotherapist (a health professional who specialises in movement and mobility). You can also choose to see a physiotherapist privately. He or she will develop a programme of rehabilitation exercises to gradually strengthen your knee and stretch your muscles. These exercises will vary depending on the kind of injury you have and how severe it is. Your physiotherapist may also use various techniques to help speed up the healing of your knee.

Braces to support your knee are occasionally used during rehabilitation, usually when an injury has been severe.


In some situations, you may need to have surgery to repair the injury to your knee. This is likely to be the case if:

  • you have ruptured your lateral collateral ligament
  • you have damaged your anterior cruciate ligament and you do a lot of sport, or have also torn cartilage or your medial collateral ligament – you may need a reconstruction operation, which involves taking a graft of tendon (usually from your kneecap) to replace the damaged ligament
  • more than one ligament or tissue in your knee has been damaged
  • you have torn your patellar tendon
  • your knee remains painful or locks after a meniscus injury

Prevention of knee injuries

There are some precautions you can take to try to reduce the risk of damaging your knee ligaments.

  • Exercise regularly to maintain a good level of fitness. This will mean your muscles are stronger and better able to support your joints, including your knees. If you haven’t been active for a while, start gently and gradually increase the intensity.
  • Spend five to 10 minutes warming up before exercise to increase blood flow to your muscles and reduce the chance of an injury. Many sports professionals advise stretching your muscles after warming up and again after cooling down; however the benefit of stretching before or after exercise is unproven.
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