Common Knee Injuries

Author: Chloe Wilson - BSc(Hons) Physiotherapy

Common knee injuries vary from minor falls which may settle quickly to major accidents which may take months to recover from. Here we will look at the  most common knee injuries including how they occur, the symptoms for each one and how to treat them.

Some injuries result from massive forces going through the knee, whereas others may be the result of simply twisting slightly wrong. The knee ligaments and cartilage are the structures most commonly damaged.

Here we have put them into four groups:

1) Ligament Injuries: damage to the ligaments that support the joint
2) Cartilage Injuries: damage to the cartilage lining the joint
3) Muscle Injuries: damaged to the muscle fibres
4) Kneecap Injuries: damage to the patella bone

You can find out more about each type of injury, including the best treatments to ensure a quick and full recovery by clicking on the links below for more info. 

Knee Ligament Injuries

There are four ligaments in the knee, which work in the pairs. The anterior cruciate ligament and posterior cruciate ligament control the forwards and backwards movement of the knee and are really important for providing stability. The medial and lateral collateral ligaments provide sideways stability for the knee.

Ligaments are usually injured either by sudden twisting movements, or when a great deal of force goes through part of the knee e.g. from a sporting tackle.  They are the most common knee injuries in sports.

1) ACL Injuries

An ACL tear or rupture is a serious injury of the knee

What is it: Anterior cruciate ligament gets overstretched and tears/ruptures

Causes: Knee bending the wrong way, pushing back too far or twisting of the knee

Immediate Symptoms: Popping sound, swelling, pain, giving way

Long Term Consequences: Lack of stability with pivoting and twisting

Treatment: Exercise rehab and/or surgery. See ACL Injuries section for more information.

2) MCL Tear

What is it: Damage to some or all of the fibres of the medial collateral ligament

Causes: Force through the outside of the knee e.g. tackle, sudden twisting of the knee e.g. skiing

Symptoms: Inner knee pain, swelling, instability, difficulty bending the knee

Treatment: PRICE, exercises, knee brace. See the MCL Tear section for more info.

3) PCL Injury

Classic presentation of a PCL injury - one of the less common knee injuries

What is it: Tear of the Posterior Cruciate Ligament that sits inside the knee joint.  One of the less common knee injuries

Causes: A force through the top of the shin bone causing the knee to bend backwards e.g. car accident or fall on to a bent knee

Immediate Symptoms: Usually fairly mild pain and swelling.  Often not noticed immediatelyThe shin bone tends to drop back from its normal position as seen in the picture here

Long Term Consequences: Instability, particuarly with activities when the knee is bent e.g. stairs, problems with running

Treatment: Knee brace, physical therapy and/or surgery. See PCL Injuries section for more information.

4) Knee Sprain

Some of the most common knee injuries involve overstretching of one of the 4 knee ligaments.

What is it: Over stretching any of the knee ligaments which tears some of the fibres. This is one of the most common knee injuries

Causes: sudden force through the knee or sudden twisting

Symptoms: knee pain, swelling, instability, difficulty bending and straightening the knee

Treatment: PRICE, exercises, knee braces. See the knee sprain section for more info.

Cartilage Injury

The knee joint is lined with 2 types of cartilage, articular cartilage which lines the bones, and then a second special layer of cartilage known as the meniscus. The meniscus works like special cushioning to reduce the force going through the knee bones.

1) Meniscus Tear

Meniscus tears are common knee injuries

What is it: Tear in the cartilage lining the knee joint. This is one of the most common knee injuries

Causes: a) Suddenly - force through the knee or sudden twisting of the knee, or b) Gradually - through wear and tear e.g. arthritis

Symptoms: knee pain, swelling, locking, instability, difficulty straightening the knee, difficulty walking

Treatment: PRICE, exercises, knee brace, tubigrip, sometimes requires surgery. Can take a long time to heal - see the Cartilage Injuries section to find out more.

Muscle Injuries

Another group of common knee injuries is muscle damage.  If the muscles around the knee are suddenly overstretched, some or all of the muscle fibres can tear. 

These are commonly referred to as muscle strains.  Treated correctly, and a full recovery is usually made in a few weeks, but if you try to return to activity too quickly, you are likely to suffer from long term problems

Calf tears are common knee injuries, particularly for runners

1) Calf Strain

What is it: Tear to some or all of the muscles fibres in one or both of the calf muscle

Causes: a) Suddenly - sudden acceleration e.g. jumping or sprinting, or b) Gradually - repetitive overuse e.g. running

Symptoms: calf pain, swelling, bruising, difficulty walking, cramp

Treatment: PRICE, exercises, tubigrip, sometimes requires surgery. Visit the Calf Muscle Strain section to find out more.

Knee Cap Injuries

Kneecap problems are less common knee injuries as they require a great deal of force through the knee.

1) Dislocated Patella

A dislocated patella is a fairly common knee injury

What is it: Knee cap get pushed out of place. This is one of the least common knee injuries

Causes: Usually caused by major, high impact injury e.g. car crash

Symptoms: Deformed leg - won’t be in a straight line. Very painful and swollen. Occasionally you lose feeling below the knee

Treatment: Relocation of the bones, exercises, knee brace, may require surgery.  Find out more in the dislocated patella section

2) Patella Fracture

Patella fractures are one of the less common knee injuries

What is it: When the kneecap bone breaks into two or more pieces.

Causes: A great force through the front of the knee e.g. falling from a height or impact from a car crash.

Symptoms: Pain and swelling at the front of the knee. Difficulty moving the knee and walking

Treatment: May require surgery, exercises, knee brace and/or cast.  Find out more in the kneecap injuries section

To find out more about each of the specific common knee injuries, including simple and effective treatment options for each, choose from the links above.

Other Common Knee Injuries

As well as common knee injuries there are a number of other causes of knee pain which tend to come on gradually rather than suddenly.

If you have a longer term knee condition or have been having knee pain for a while but don’t know what’s wrong, then go to my section devoted to common knee conditions or visit the knee pain diagnosis section for help working out what is causing your knee pain.

You can also find a wide range of treatment options in the knee pain treatment section. 

Go to Knee Pain Guide


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