Knee injuries

Expert reviewer Dr Roger Tillman, Consultant Orthopaedic Surgeon
Next review due October 2021

Knee injuries can cause pain, swelling and instability (the feeling that your knee is going to give way). They’re often caused by ligament damage. Your knee ligaments are bands of tissue that help to keep your knee stable by holding the bones together. You can also hurt other tissues around your knee, such as your cartilage and tendons.

An image showing the different parts of the knee

Types of knee injury

Knee ligament injuries

You have two sets of ligaments in your knee. The collateral ligaments run down either side of your knee, while the cruciate ligaments lie inside your knee. If different ligaments get damaged, this can lead to different types of knee ligament injuries.

  • Collateral ligament injuries – the medial collateral ligament (MCL) is on the inner side of your knee and the lateral collateral ligament (LCL) is on the outer side. They limit how much your knee can move from side to side. You can sprain or tear your MCL if your lower leg gets forced outwards from a direct blow to the side. This may happen when you’re skiing. Your LCL is less likely to be injured but may be damaged if your lower leg gets forced inwards. Both ligaments may also be damaged if your knee twists too far outwards.
  • Cruciate ligament injuries – cruciate means cross-shaped. Your anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) form a cross inside your knee. They help to keep your knee stable by controlling how much it moves backwards and forwards. ACL injuries are one of the most serious types of knee injury. They often happen when you twist your knee, such as when you land on your leg then quickly turn. You may get this type of injury when you’re playing football or basketball. Your PCL may get damaged if you fall on your knee while it’s bent. Another typical way of damaging your PCL is when your knees hit the dashboard during a car accident.

If you’ve damaged one of your ligaments, a doctor may grade your knee ligament injury to show how bad it is. This will help to work out how it needs to be treated and how long it will take to heal.

  • Grade 1 is a stretch of the ligament without tearing it.
  • Grade 2 is a partial tear of the ligament.
  • Grade 3 is a complete tear through the ligament.

You’re most likely to damage your MCL and ACL knee ligaments.

Other soft tissue injuries

You can damage other soft tissues around your knee, such as your cartilage and tendons. Soft tissue means any tissue in your body that isn't bone.

  • Cartilage injuries – tearing a meniscus (one of the wedge-shaped pieces of cartilage lying inside your knee) is one of the most common knee injuries. It’s what people usually mean when they say they have a ‘torn cartilage’ in their knee. You can damage a meniscus if you play a sport that involves twisting, such as football or basketball. But this can also happen to runners, tennis players and skiers. As you get older, your menisci may become worn. This makes them more likely to tear during your normal daily activities. Your knee also has cartilage covering the parts of your bones that lie inside the joint. This articular cartilage can become damaged too, often at the same time as the other soft tissue injuries.
  • Tendon injuries – if you’re a regular runner or take part in sports where you jump a lot, you may damage the tendons that attach muscles to your knee. You can irritate or tear the tendon that connects your kneecap (patella) to your thigh muscle. This tendon is called the quadriceps tendon. Or you may irritate soft tissue around your kneecap, including the patellar tendon just below your kneecap (jumper’s knee).

Symptoms of knee injuries

Most people with a torn knee ligament have similar symptoms. These include:

  • pain
  • swelling
  • instability – you may feel like your knee is giving way

You may also:

  • feel or hear a popping or snapping when the knee ligament injury happens
  • find that you can't put your full weight on the leg with the torn ligament

If you injure a meniscus in your knee, you may:

  • feel severe pain and your knee may swell after a few hours
  • have a ‘locked’ knee that you can’t move in the usual way
  • still be able to walk a little on the leg where you have the knee injury

If you’ve torn your tendons, you may notice some pain and swelling. You may also find that:

  • your kneecap is lying higher or lower than it should be
  • you won’t be able to straighten your knee

If you’ve injured your knee and your pain is mild or moderate or has come on gradually, visit your GP or physiotherapist.

If you’ve hurt your knee in an accident, your pain is very bad or your knee is badly swollen, go to your nearest A&E department.

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Diagnosis of knee injuries

Your doctor will ask about your symptoms and check your knees. They may feel for fluid in your knee joint by pressing gently around your kneecap. They’ll also ask you to describe how you hurt yourself, where your pain is and what type of pain it is.

Your doctor may ask you to walk, sit or lie down. This is so they can test for any injury to your knee ligaments or soft tissues. They’ll bend and straighten your knee and move your leg into different positions.

If your doctor believes that your knee injury will heal better with surgery, they’ll refer you to an orthopaedic surgeon. This is a doctor who specialises in bone surgery.

Your doctor may recommend some other tests.

  • An X-ray or CT scan – this can check for a broken bone (fracture) or arthritis.
  • An MRI scan – this is useful if your doctor is not sure about the diagnosis. It may help to show up damage to the cartilage or soft tissues of your knee after an injury.
  • Knee aspiration – your doctor may remove a sample of fluid from your knee to look for blood.
  • Knee arthroscopy – your surgeon may look inside your knee using a telescope attached to a tiny camera. This can help to show if there’s damage to a meniscus, cartilage or ligament. Your doctor may treat your damaged knee at the same time as doing the arthroscopy.

Treatment of knee injuries

A doctor or physiotherapist may suggest several different treatments, depending on what you’ve done to your knee and how bad the damage is. It’s frustrating, but it’s important to be patient while you recover – your injury may take time to fully repair itself. You may not be able to do all the things you’re used to doing for some time.

Self-help for knee injuries

You should follow the POLICE procedure for any soft tissue injury to your knee.

  • Protect your knee from further harm.
  • Optimal loading It’s important to start moving the muscle again sooner rather than later. Remember to only do what feels comfortable and speak to a physiotherapist for further advice.
  • Ice the painful area with a cold compress, such as ice or a bag of frozen peas wrapped in a towel. Do this for 20 minutes every two hours during the day for the first two to three days. Don't put ice directly onto your skin as this can damage it.
  • Compress the joint with a simple elastic bandage or elasticated tubular bandage to support your knee and help decrease swelling. Don’t leave the bandage on while you sleep.
  • Elevate your knee by raising it above the level of your heart, keeping it supported.

An image describing the acronym PRICE

There are certain things you shouldn’t do in the first three days after your injury so you don’t cause any more damage to your knee. You can remember these as HARM.

  • Heat – don’t take hot baths, showers or saunas or use a heat pack.
  • Alcohol – don’t drink alcohol as this can increase bleeding and swelling in your affected knee.
  • Running or other forms of exercise – these may cause further damage.
  • Massaging your injured knee – this can cause more swelling or bleeding.

An image describing the acronym HARM

Medicines for knee injuries

Paracetamol is the best medicine to ease your pain if you have a knee injury. You can buy it over the counter from pharmacies.

Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, can help to reduce inflammation and swelling, as well as ease pain. But you shouldn’t take oral NSAIDs (tablets or capsules) for the first two days after your injury because they may delay healing. You can buy NSAID gels, creams and sprays that you can put directly onto your skin as soon as you’ve injured yourself.

Your doctor may prescribe stronger painkillers containing codeine if your pain is very bad. Always read the patient information that comes with your medicine and if you have questions, ask your pharmacist or doctor for advice.

Physiotherapy for knee injuries

If your injury is more severe, or it doesn’t seem to be improving over time, your GP may refer you to a physiotherapist. A physiotherapist is a healthcare professional who specialises in movement and mobility. You can also choose to see a physiotherapist privately.

A physiotherapist will create a programme of exercises to gradually strengthen your knee so you can move it normally again. The exact exercises will depend on how you’ve injured yourself, and how badly. But you’ll probably be given exercises to do every day at home, as well as at your physiotherapy appointments.

Some people have braces or strapping to support the knee during rehabilitation, usually when an injury has been severe.

Surgery for knee injuries

For some knee injuries, your doctor or physiotherapist may refer you to an orthopaedic surgeon. The surgeon may recommend that you have surgery to repair the damage to your knee – especially if other treatments haven’t worked.

Your surgeon is more likely to suggest surgery if you have one of the following injuries.

  • You’ve torn your anterior cruciate ligament (ACL), especially if you do a lot of sport or have also torn a meniscus. ACL reconstruction involves taking a piece of tendon (usually from your patella tendon or hamstring) to replace the damaged ligament.
  • Your knee is still painful or locks after an injury to your meniscus. Your surgeon may repair or partially remove your damaged meniscus.
  • You’ve injured your medial collateral ligament (MCL) and it hasn’t healed after three months of non-surgical treatment. Your surgeon may repair or reconstruct your MCL.

You may be able to have a type of keyhole surgery called knee arthroscopy to get to the damaged area of your knee.

Causes of knee injuries

You may hurt your knee if:

  • you bang your knee so it moves beyond its usual range of movement – this may happen during a fall or if you land awkwardly
  • you play a sport such as football that combines running, jumping and stopping with quick changes of direction
  • you twist your knee, especially in certain sports, such as football or basketball
  • your knees hit the dashboard in a car accident, which can damage your posterior cruciate ligament

You’re more likely to have a knee ligament injury if:

  • you have osteoarthritis of your knees, as this may damage your ligaments and cartilage as well as your bone
  • you’re not taking precautions when you exercise. This includes not warming up before you do anything active or cooling down afterwards

Prevention of knee injuries

There are several precautions you can take to try to reduce your chances of damaging your knee ligaments. This will help to avoid other sports injuries too.

  • Exercise regularly to keep your fitness levels up, and include some resistance training (training with weights). Regular exercise means your muscles are stronger and more flexible, so they can support your joints, including your knees. If you haven't been active for a while, start off gently and gradually increase the number, length and intensity of your exercise sessions.
  • Warm up before you exercise, and cool down afterwards. Spend five to 10 minutes warming up before doing any exercise to increase blood flow to your muscles and reduce the chance of an injury.
  • Wear the right footwear. If you have well-fitting shoes that are designed for the activity you’re doing, they’ll support your foot and ankle and help to prevent injury. There are many different models of trainers available and it’s important to find some that fit well and offer the support and cushioning you need. If you’re not sure, it’s a good idea to visit a specialist sports shop and ask for advice.
  • Wear comfortable clothing, so you can move your knees easily without any restrictions.
  • Don’t exercise or play sport when you’re in pain.

Frequently asked questions

  • Your healing and recovery time depends on which part of your knee you’ve injured and how badly it’s affected.

    If you have slightly sprained your medial collateral ligament (MCL), you may be able to go back to sport again in two to three weeks. But if your MCL sprain is a bad one, this can take up to 12 weeks. You may even need to wear a knee brace to protect your knee and have physiotherapy for three months or longer. You may also still have some pain afterwards and may be prone to injuring yourself again.

    If you have surgery to repair your injury, it can take up to 12 months to get back to your previous levels of activity. You’re likely to return to sports involving little or no contact (such as gymnastics or basketball) more quickly than contact sports (such as rugby).

    Returning to sports and other physical activities too quickly may mean you’re more likely to hurt yourself again. So always follow your doctor or physiotherapist’s advice and exercise recommendations.

  • Some people use arnica for soft tissue injuries such as sprains and strains. Arnica has been used for centuries as a homeopathic (very, very diluted) remedy that you put in your mouth. It’s also been used as a herbal remedy, in the form of creams, gels or ointments that you put directly on your skin.

    Some medical research has shown that putting arnica on your skin may help a little to ease sore joints. But arnica can cause more side-effects than topical painkillers, such as ibuprofen, and more research is needed. So doctors don’t usually recommend people use arnica products.

  • If you have osteoarthritis, the muscles around your knee joint can weaken. This may make you more likely to injure your knee. You may not also put your full weight on your knee, which means you’re more likely to fall over.

    By keeping active and regularly exercising your knees, you can strengthen your muscles to help prevent injuries. Exercise may also ease your knee pain so you’re more likely to keep moving and exercising your joints regularly. The NHS recommends people do at least 30 minutes of moderate-intensity exercise on at least five days each week. But if this is too much for you, even just five to ten minutes at a time can help to strengthen your joints and benefit your health.

    Aim to do a combination of different types of exercise.

    • Strengthening exercises – these will help to strengthen the muscles around your joints.
    • Aerobic exercise – this increases your heart rate and makes you slightly out of breath. Examples include swimming, cycling and walking, but even daily activities such as housework and gardening are types of aerobic exercise too. Aerobic exercise can ease your arthritis symptoms and help you keep your weight under control. This means your knee problems may be less likely to get worse in the future.
    • Range-of-movement exercises and stretches – these may help to keep you flexible and mobile. You move your joints through their full range of movement and then try to move them a little beyond this.
    • Try to do exercise regularly – little and often is often best. Speak to a physiotherapist about the best types of exercise for you and always follow their advice.
  • Housemaid’s knee is the common name for the medical condition called prepatellar bursitis. It’s often caused by the pressure of kneeling forwards for long periods. These days, prepatellar bursitis is often seen in carpet fitters or roofers – anyone who spends a lot of time working on their knees.

    If you have prepatellar bursitis, the bursa in front of your kneecap will become inflamed (swollen). A bursa is a small fluid-filled sac (bag) that acts as a sort of cushion or lubrication. It’s usually found in and around your joints to prevent friction and keep your joints moving easily. When a bursa becomes inflamed (called bursitis), it swells up with fluid. The bursa between your kneecap and the skin that lies over is your prepatellar bursa.

    Prepatellar bursitis can also be caused by a direct blow to your knee or a fall. It’s more common in people who have gout or rheumatoid arthritis. Sometimes, prepatellar bursitis is caused by a bacterial infection, especially in children.

    If you have prepatellar bursitis, you may have:

    • swelling over the front of your kneecap
    • pain in your knee – this is worse when you bend it
    • difficulty kneeling and walking
    • redness of the skin over your knee

    If you have an infection, your knee may look red, feel hot and painful. You may also have a raised temperature. Always see your GP if you have these symptoms.

    You can usually treat prepatellar bursitis at home with simple self-help measures. Your GP will recommend that you rest and put an ice pack on your knee. See the Self-help for knee injuries section above. Try to avoid doing the activity that caused the inflammation in the first place.

    Your GP may also recommend over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen. These will reduce your pain and inflammation.

    You may find it helpful to use a stick or cane when you walk. Your GP may also refer you to a physiotherapist if you’re finding it hard to move your knee.

    If your GP thinks your prepatellar bursitis is caused by an infection, they’ll prescribe antibiotics. They may also take a small sample of fluid from the bursa through a needle (aspiration). They’ll send the fluid to a laboratory to look for and identify any bacteria. The laboratory may also find certain crystals in the fluid if you have gout or rheumatoid arthritis.

    You can reduce your chances of getting prepatellar bursitis by wearing knee pads while you work, or kneeling on a cushion. Also try to take regular breaks, or change what you’re doing to give your knees a rest.

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  • Reviewed by Graham Pembrey, Lead Editor, Bupa Health Content Team, October 2018
    Expert reviewer Dr Roger Tillman, Consultant Orthopaedic Surgeon
    Next review due October 2021