Knee injuries
Your health expert: Mr Damian McClelland, Trauma and Orthopaedic Consultant, and Clinical Director for Musculoskeletal Services at Bupa
Content editor review by Rachael Mayfield-Blake, July 2021
Next review due July 2024
Knee injuries can cause pain, swelling, and the feeling that your knee is going to give way (instability). Often it’s the ligaments that are damaged. These are bands of tissue that hold your bones together. You can also hurt other tissues around your knee, such as your cartilage and tendons.
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.
Collateral ligament injuries
Your 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 you get a direct blow to the outside of your knee, which stretches the inner side of your knee. This may happen when you’re skiing, for example.
- You’re less likely to injure your LCL but it can happen if your lower leg gets forced inwards. This stretches the outer side of your knee.
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. This might happen when you’re playing football or basketball, for example.
- Your PCL may get damaged if you fall on your knee while it’s bent. Another way of damaging your PCL is when your knees hit the dashboard during a car accident.
If one of your ligaments is damaged, a doctor may grade your knee ligament injury to show how bad it is. This will help to work out what treatment you need and how long your knee injury 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.
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
One of the most common knee injuries is to tear a meniscus (one of the wedge-shaped pieces of cartilage that lie inside your knee). This can happen if you play a sport that involves twisting, such as football or basketball. But it can also happen when you run, play tennis and ski. As you get older, your menisci may become worn, which makes them more likely to tear during normal daily activities. Your knee also has a different type of cartilage that covers the ends of your bones that lie inside the joint. This articular cartilage can get damaged too.
Tendon injuries
If you run regularly or play 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).
Prepatellar bursitis
Housemaid’s knee is the common name for prepatellar bursitis. It’s often caused by the pressure of kneeling forwards for long periods. The bursa (a small fluid-filled sac that acts as a cushion or lubrication in front of your kneecap) will swell up with fluid. Prepatellar bursitis can also be caused by a direct blow to your knee or a fall, or a bacterial infection.
Causes of knee injuries
You may injure 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 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’ve knee osteoarthritis, as this can weaken the muscles around your knee joint, which increases your risk of injury
- you’re not taking precautions when you exercise like not warming up before you do anything active or cooling down afterwards
Symptoms of knee injuries
If you have a torn knee ligament, symptoms may include:
- pain
- swelling
- instability – you may feel like your knee is giving way
You may also:
- feel or hear a pop or snap at the time you injure your ligament
- find you can't put your full weight on your leg
If you injure a meniscus in your knee, you may:
- have 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 your leg
If you’ve torn your tendons, you may notice some pain and swelling. You may also find:
- your kneecap is lying higher or lower than it should be
- you won’t be able to lift your knee
If you have prepatellar bursitis, you may have:
- swelling over the front of your kneecap
- pain in your knee that’s worse when you bend it
- difficulty kneeling and walking
- red skin over your knee
If you have an infection, your knee may look red, feel hot and painful. You may also have a high temperature. Always see your GP if you have these symptoms.
If you injure your knee and the pain is mild or moderate or has come on gradually, you can visit your GP or a 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.
Diagnosis of knee injuries
Your doctor will ask about your symptoms and examine you. 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 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 you need surgery, they’ll refer you to an orthopaedic surgeon (a doctor who specialises in bone, tendon and ligament surgery).
You may need to have some other tests too.
- An X-ray or CT scan – this can check for a broken bone (fracture) or arthritis.
- An MRI scan – this 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.
- 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.
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Self-help for knee injuries
If you injure your knee, you should follow the POLICE and HARM procedures. POLICE stands for protect, optimal loading, ice, compression and elevation – things you should consider doing if you have injured your knee. And HARM stands for heat, alcohol, running and massage – things that you should avoid for a bit so you don’t damage your knee further.
To find out more about POLICE and HARM, you can visit our page on what to do if you injure your knee.
Treatment of knee injuries
Your doctor or physiotherapist may suggest 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.
Medicines for knee injuries
Over-the-counter painkillers, such as paracetamol and ibuprofen, can help with the pain if you injure your knee. You can also use anti-inflammatory gels and creams to help with pain relief.
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 get better over time, your GP may refer you to a physiotherapist. 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 your physiotherapist will probably give you exercises to do every day at home, as well as at your follow-up appointments.
You may need to use a brace to support your knee while it recovers, usually if your injury was severe.
Surgery for knee injuries
Your doctor or physiotherapist may refer you to an orthopaedic surgeon for some knee injuries. You may need surgery to repair the damage to your knee – especially if other treatments haven’t worked.
Your surgeon is more likely to suggest you have an operation 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. In ACL reconstruction, your surgeon will take 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 other treatments. 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.
Prevention of knee injuries
There are several things you can do to reduce your chance of damaging your knee ligaments. This will help to prevent other sports injuries too.
- Exercise regularly to keep your fitness levels up, and include some resistance training (training with weights). Regular exercise will make your muscles 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.
- Wear the right footwear. It’s important that your trainers fit well and you replace them when they wear out. If you’re not sure about the fit, visit a specialist sports shop for advice.
- Wear comfortable clothing that doesn’t restrict you.
- Don’t exercise or play sport when you’re in pain.
- Wear knee pads while you work, or kneel on a cushion to reduce your chances of getting prepatellar bursitis. And take regular breaks.
How long your knee injury takes to heal depends on which part of your knee you’ve injured and how badly it’s affected. If you play sports or go running too soon, you’re likely to hurt yourself again. So always follow your doctor or physiotherapist’s advice.
See our Treatment of knee injuries section for more information.
Some people use arnica for soft tissue injuries, such as sprains and strains. Some research has shown that putting arnica on your skin may help to ease sore joints. But it can have more side-effects than other painkilling creams, such as ibuprofen. So, doctors don’t usually recommend it.
Osteoarthritis can weaken the muscles around your knee joint, which increases your risk of injury. If your knee is painful from arthritis, you might not put your full weight on it and you may be more likely to fall over. Regular strengthening and stretching exercises can help reduce your risk of a knee injury.
Housemaid’s knee is the common name for 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.
See our Types of knee injury section for more information.
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