There are four main ligaments in the knee that can become injured. During injury, a knee ligament may be sprained (stretched), or sometimes ruptured (torn). Ligament rupture can be partial (just some of the fibres that make up the ligament are torn) or complete (the ligament is torn through completely). Knee ligament injuries can cause pain, swelling, tenderness, bruising and reduced movement of your knee. Your knee joint may feel unstable and you may walk with a limp. Treatment of a knee ligament injury can depend on a number of things including which ligament is injured and how sporty and active you are.
The diagrams above show the knee joint.
There are four bones around the area of the knee joint: the femur (thigh bone), the tibia (the main shin bone), the fibula (the outer shin bone) and the patella (the knee cap). But the main movements of the knee joint are between the femur, the tibia and the patella. Articular cartilage (tough connective tissue) lines the ends of the tibia and femur and the back of the patella around the knee joint. The articular cartilage reduces friction between the bones of the knee joint and helps smooth movement between them.
Each knee joint also contains a medial and lateral meniscus (inner and outer meniscus). These are thick rubbery pads of cartilage tissue. They are C-shaped and become thinner towards the middle of the joint. The menisci cartilages sit on top of, and are in addition to, the usual thin layer of articular cartilage which covers the top of the tibia. The menisci act like shock absorbers to absorb the impact of the upper leg on the lower leg and also help to improve smooth movement and stability of the knee.
There are also four ligaments around the knee joint. A ligament is a tough strip of connective tissue that joins one bone to another bone around a joint. The knee joint ligaments help to stabilise and support the knee when it is moved into different positions.
Each ligament has a different job to do:
The knee joint is surrounded by a protective joint capsule. This is lined by a special membrane called the synovial membrane. The synovial membrane produces synovial fluid which helps to lubricate and reduce friction within the knee joint. There are also muscles that help to support the knee joint. The main ones are the quadriceps (front thigh muscles) and hamstrings (rear thigh muscles) in the legs.
The ligaments around the knee are strong. However, sometimes they can become injured. They may be sprained (stretched), or sometimes ruptured (torn). A ligament rupture can be partial (just some of the fibres that make up the ligament are torn) or complete (the ligament is torn through completely). The majority of knee ligament injuries are sprains and not tears and they tend to settle down quickly.
There are a number of different things that can cause injury to the ligaments in your knee:
ACL injury most often occurs during sports such as football, basketball, skiing and tennis. The injury often happens if you land on your leg and then quickly pivot or twist your knee in the opposite direction.
Women are more likely to injure their ACL than men although it is not certain why this is. About half of people with an ACL injury also have injury to their meniscus or another ligament in the same knee.
Injury to this ligament is not as common as an ACL injury. This is because the PCL is wider and stronger than the ACL. There are a number of ways that the PCL can become injured. For example, it may be injured during a car accident if the front of your bent knee hits the dashboard. It may also be injured from falling on to your bent knee. Your PCL can also be injured if your knee is hit from the front whilst your leg is stretched out in front of you with your foot on the ground - for example, during a game of football.
At first, some people with a PCL injury may not have much in the way of symptoms (see below). It may take a while for you to realise that there is a problem. For example, you may later notice pain that comes on when going up and down stairs or when starting a run; or, your knee may feel unstable when walking on uneven ground.
Injuries to the MCL can happen in almost any sport and can affect people of all age groups. They often happen when your leg is stretched out in front of you and the outer side of your knee is knocked at the same time - for example, during a rugby or football tackle.
Injury to the LCL is less common than injury to the MCL. This is because your other leg usually protects against injury to the inner side of your knee. (It is usually a direct blow to the inner side of your knee that causes an LCL injury.) But, this ligament injury can sometimes happen if one leg is stretched out in front of you and doesn't have the other leg for protection - for example, during a rugby or football tackle.
If you have injured one or more of the ligaments in your knee, the symptoms are likely to be similar regardless of the ligament that is injured. The severity of the symptoms depends on the degree of the injury to the ligament. For example, a ligament that is completely torn may produce more in the way of symptoms than a ligament that is just sprained (stretched).
Symptoms can include:
If you feel that you may have a knee ligament injury, you should see a doctor. Your doctor will usually start by asking you questions about the injury, what happened and where you are feeling any pain. They may then examine your knee to look for signs of swelling of your knee joint. They may also move your leg into different positions to test your knee ligaments. From this examination, they may be able to get an idea of the possible injury that you have.
If your doctor is concerned that you may have a more serious knee ligament injury, they may refer you for further tests such as an ultrasound scan or an MRI scan. Such tests should be able to show up any tears or rupture of your ligaments. Sometimes, an X-ray of your knee may be suggested.
If you have a lot of swelling of your knee after your injury, doctors may sometimes suggest draining off some of the fluid that is causing the swelling in your knee. To do this, a needle can be used to pierce the skin around your knee and the fluid can be drained off into a syringe attached to the needle. Special precautions are taken to keep the area and the procedure sterile so as not to introduce infection into your knee joint.
For the first 48-72 hours think of:
Paying the PRICE:
Avoid HARM for 72 hours after injury. That is, avoid:
This may be helpful after some knee ligament injuries. Physiotherapy may help to improve the range of movement in your injured knee. Exercises may also be suggested to help strengthen the muscles that support your knee joint. If you are considering surgery to repair a torn knee ligament, you may be advised to have physiotherapy before the operation.
Depending on the knee ligament injury that you have, your doctor may advise you to wear a special brace to support your knee while the damaged ligament heals. Knee braces usually have a hinge mechanism that allows some bending and extending movement of your knee joint but not movement of your knee from side to side. However, a knee brace may not be advisable for all knee ligament injuries. You may like to discuss the use of a knee brace with your doctor.
Sometimes surgery may be suggested after a knee ligament injury. This is more likely if:
Surgery is most commonly suggested to repair ACL injuries. However, it is fair to say that the best way to treat a torn ACL is still debated. Physiotherapy and other measures may be all that is needed by some and may prevent the need for an operation. The decision about whether or not to use surgery depends on each individual person, the activities and sports that you do, how active your lifestyle is in general, your underlying health and any other knee injuries that you may also have. You may want to discuss the pros and cons of surgery with your doctor.
If surgery is carried out to repair a torn ACL, your doctor will usually advise that you wait some weeks after your initial injury. This is so that any swelling has had a chance to go down, you have got more movement back in your knee and you have built up the strength in the muscles of your thighs that help to support your knee joint. Your doctor may refer you for physiotherapy to help to prepare you for surgery.
The ACL ligament cannot simply be stitched back together. Instead, surgery to reconstruct, or rebuild, the ACL is usually carried out. Most often, part of a tendon, or tendons, from somewhere else in your body is used to reconstruct your ACL. For example, the following may be used:
The tendon is fixed in place inside your knee joint, using staples or screws. Once fixed in place, over time, a new ligament should grow over the tendon that has been used. Keyhole surgery is usually used to reconstruct your ACL.
There is currently some debate as to the best way to treat PCL injury - with surgery, or without surgery. You may like to discuss this with your doctor. If surgery is carried out, as with surgery for ACL injury, the damaged ligament is replaced using a tendon, or tendons, from elsewhere in your body, or using a donor tendon.
Surgery is not often needed for MCL injuries.
This will depend on which knee ligament you have injured and also how severe your injury is. Also, if you have injured more than one ligament in your knee, recovery may take longer.
If you have surgery to repair your ACL, it usually takes around six months before your knee has recovered enough for you to return to your previous sporting activities but, in some people, it may be longer. In general, surgery to reconstruct an ACL has good results in around 8-9 out of 10 people.
If your PCL has been treated using surgery, it can take between 9 and 12 months before complete recovery.
After a sprain or partial tear to the MCL, the ligament has completely healed in most people after three months. If there is a complete tear, recovery may take a little longer but most people are back to their usual activities after 6-9 months.
Note: you should ask advice from your doctor or physiotherapist about when it is safe for you to start exercise or sport again after a knee ligament injury. It is important that you do not start exercising again until your knee is pain-free and completely stable. If you start exercising too early, you may cause further injury to your knee.
Knee ligament injuries can be unpredictable and can affect anyone, including fit people who do a lot of sport. However, if you exercise regularly and build up the strength in the muscles of your legs that help to support your knee joint (particularly your hamstring and quadriceps muscles), this may help to reduce your chance of knee ligament injury. If you are not used to exercising regularly, you should start gently and gradually build up the frequency and intensity of your exercise. See separate leaflet called 'Physical Activity for Health' for more details.
During an exercise session, or if you are playing sport, make sure that you warm up at the start of your training. This increases the flow of blood to your muscles and helps to loosen up your joint movements. Warming up may also help to prevent injury.
Some people wear a knee brace when they are exercising or doing sporting activities if they have previously had a knee ligament injury, or even just to prevent a knee injury in the first place. Some studies have shown that wearing a brace may help to reduce the chance of another injury whilst other studies have not shown this as the case. One particular study looked at people with previous injury to their ACL. The study found that those who wore a knee brace whilst skiing were less likely to have a further knee injury than those who did not wear a knee brace. In general, more research is needed to look at the use of knee braces for preventing knee injury.