How do knee ligaments get injured?
Knee ligament injuries occur when one or more of the ligaments in and around the knee joint are twisted (sprained) or torn (ruptured). Your knee ligaments are bands of tissue that hold the bones together, keeping your knee stable.
You can rupture a ligament partially (the ligament still stays intact) or completely (completely torn through).
There are two sets of ligaments in your knee:
- the anterior and posterior cruciate ligaments, that control forward and backward movement of the knee joint
- the medial and lateral collateral ligaments, which control side to side movements
Knee ligament injuries most commonly occur when you receive a blow to the knee, have a fall, make a sudden movement, or land awkwardly while playing sport. Anterior cruciate ligament (ACL) injuries are one of the most common types of knee ligament injury.
Most knee ligament injuries may heal on their own in time with self-care techniques and, sometimes, physiotherapy. However, surgery may be needed in some cases.
What are the symptoms of a knee ligament injury?
Knee ligament injuries tend to produce similar symptoms, regardless of the ligament injured. How severe your symptoms are may depend on how bad the injury is.
Symptoms of a knee ligament injury may include:
- knee pain
- knee swelling
- a popping sound or snapping feeling at the time of injury
- difficulty walking
- feeling like your knee may give way on weight bearing
- loss of a range of knee movements
- bruising around the knee
How did I injure my knee ligament?
Each of the four knee ligaments can become injured in different ways.
Anterior cruciate ligament (ACL)
ACL injuries are one of the most common knee injuries. They often happen when a person lands on their leg and quickly twists their knee in the opposite direction. This type of injury occurs most commonly when playing sports, such as football or basketball.
Posterior cruciate ligament (PCL)
PCL injuries can happen in many ways. These include:
- falling onto your knee while it is bent
- during a car accident, when your knees hit the dashboard
- receiving a blow to the front of your knee while your leg is stretched in front of you and your foot is on the ground
Medial collateral ligament (MCL)
MCL injuries tend to happen if something hits the outer part of your leg while it is stretched out in front of you, such as during a football tackle. It can also happen when your knee twists outwards. MCL injuries can happen in almost any sport and at any age.
MCL injuries are most common in young adults aged 20 to 35 because they are most likely to engage in high-risk sports. However, older, less active adults can also develop MCL injuries, usually from a fall.
Lateral collateral ligament (LCL)
You are less likely to injure your LCL compared to your MCL. LCL injuries can be caused by a direct blow to the inner side of the knee. This can happen when one leg is stretched out in front of you without the other leg for protection, such as during a rugby or football tackle.
How is a knee ligament injury diagnosed?
Your doctor may suspect a knee ligament injury after asking you about your symptoms, how you injured yourself, your medical history, and performing an examination of your knee.
Your doctor may also recommend some tests, such as:
- an X-ray – to check for a broken bone
an MRI scan – to help make the diagnosis, if it is unclear
- knee aspiration – to look for blood in the knee
- knee arthroscopy – occasionally, a keyhole procedure may be used, and your knee surgeon may also treat your knee at the same time
What is the treatment for a knee ligament injury?
If you have injured your knee, you should see your doctor who will be able to advise you on the best treatment. The treatment you need will often depend on how severe your injury is, your desired level of activity, and whether you have injured other parts of your knee. For less serious injuries, the following self-help techniques can be used at home initially to help treat the injury.
Self-Help: PRICE therapy
PRICE therapy for the first 48 - 72 hours involves:
- Protection – protect your knee from further injury by using a knee support
- Rest – avoid exercise and reduce your daily activities, possibly with the help of crutches. You can then gradually start moving your knee, based on your doctor’s advice
- Ice – apply ice to your knee for 15-20 minutes every two to three hours during the day. Ice can be wrapped in a damp towel or use a bag of frozen peas. Do not place the ice directly onto your skin because it could cause a cold burn
- Compression – compress the knee with an elasticated bandage to reduce any swelling and to help keep your knee joint still. The bandage should be snug but not so tight that it restricts blood flow. Remove the bandage before you go to sleep
- Elevation – keep your knee raised above the level of your heart to reduce swelling, for example using a supported pillow
Self-Help: Avoiding HARM
Avoiding HARM for 72 hours after the injury. This involves avoiding:
- Heat – this includes hot baths, saunas or heat packs, which may encourage bleeding
- Alcohol – drinking alcohol may increase bleeding and swelling and decrease healing
- Running – or any other form of exercise that could cause more damage
- Massage – which may increase bleeding and swelling
Painkillers, such as paracetamol, can be used to help ease any pain.
Ibuprofen and other over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) can help relieve pain and may also limit inflammation and swelling. Some guidelines suggest you should avoid taking NSAIDs for the first 48 hours after the injury. This is because it is thought that NSAIDs may slow down the healing process. However, this is currently a theory that needs further research. At present, there is no conclusive evidence that proves that NSAIDs should not be taken soon after an injury.
It may not be safe to take NSAIDs if you have certain conditions (such as asthma, high blood pressure, kidney failure, indigestion or heart failure) or if you are allergic to NSAIDS. Always check with your doctor or pharmacist before taking new medicines after an injury.
Your doctor may refer you to a physiotherapist to help you improve the strength of the muscles around your knee and the range of movement of your knee joint. They will be able to tailor an exercise programme for you to follow. The exact exercises and how often you do them will depend on the type of injury and how severe your injury is. In some cases, you may need a special brace to support your knee while your injury heals.
In some cases, your doctor may refer you to an orthopaedic surgeon for surgery. This usually involves a keyhole procedure to repair any ligament damage.
Surgery is more likely if:
- your injury has not improved despite physiotherapy and rehabilitation
- you are a very active person and you have injured your ACL
- you have injured more than one knee ligament, or you have also injured other parts of your knee
- you have torn your LCL
The decision about whether or not surgery may be helpful depends on:
- your age and underlying health – older people who are not very active may be less likely to need surgery
- your lifestyle – for example, whether you will be able to follow the rehabilitation programme after having surgery
- how active you are and whether you play sports – you may need to have surgery if you play sports regularly
- how unstable your knee is – if your knee is very unstable, you are at increased risk of doing further damage without surgery
- whether you have any other knee injuries
How long does it take for a knee ligament injury to recover?
It may take time to make a full recovery after you have injured one of your knee ligaments.
How soon you recover will depend on:
- which ligament was injured
- how many ligaments were injured
- how severe your injury is - for example, if it is a sprain, partial tear or complete tear
Returning to sport or exercise too soon after a knee ligament injury can put you at risk of further injury. Always ask your doctor about when it is safe for you to start exercising or playing sport again after a knee ligament injury.
To find answers to any other health questions you might have, visit our Health A-Z.