The ACL is one of the main stabilising ligaments in the knee, connecting the thighbone to the shin bone. ACL injuries are increasingly common, particularly during sports such as football, tennis, squash, rugby and skiing, and currently affect around 40,000 people in the UK each year, including increasing numbers of children.
Knee ligament injuries
Knee ligaments connect the bones and cartilage, as well as holding together and supporting the knee joint. They are made of tough, rubbery connective tissue. Four major ligaments support and stabilise the knee and these can be injured during sports such as rugby, tennis, football or skiing.
- The main ligaments in the knee are the two cruciate ligaments – the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL); these are in the middle of the knee, crossing over each other centrally
- The collateral ligaments are the medial (inner) collateral ligament (MCL) and the lateral (outer) collateral ligament (LCL)
- As well as the four major ligaments, the anterolateral ligament (ALL) runs along the outside of the knee and is often damaged at the same time as the ACL
QUICK LINKS
Anterior cruciate ligament (ACL) injuries
The ACL is in the middle of the knee and controls rotation as well as the forward movement of the shin on the thigh bone. If it’s torn, the knee becomes unstable when it is twisted and can give way, as well as losing its full range of movement. As the knee gives way, the delicate structures inside it, as well as the joint surface and meniscal cartilages, frequently become damaged.
Anterior cruciate ligament (ACL) injuries
What causes an ACL injury?
The ACL is often injured when the knee is suddenly twisted, for example when a footballer or tennis player changes direction. Injuries are also common in sports where you:
- Stop suddenly and change direction, for example during football
- Collide with someone, for example during a rugby tackle
- Land awkwardly from a jump, for example during netball or gymnastics
What are the symptoms of an ACL injury?
When the ACL tears (ruptures) there is often a popping sound, as well as pain and swelling in the knee, usually within an hour of the injury. Patients usually hobble for a week or so and then things can settle down.
In around 20% of cases, people with an ACL tear can continue with normal activities. However, most people have ongoing symptoms including knee instability (where the knee gives way, especially when you change direction while walking or running) as well as recurrent pain. Having early treatment can prevent further damage being caused to surrounding tissue each time the knee gives way. This includes cartilage injuries and meniscal tears (which affect around 70% of people who have torn their ACL) as well as arthritis.
How is an ACL injury diagnosed?
Your consultant will discuss your symptoms with you and examine your knee to check for tenderness, stiffness, swelling and any other problems. He may also ask you to move your knee into different positions to assess your range of movement and the function of the joint.
In most cases, they will arrange for you to have an X-ray to confirm the diagnosis. He will also arrange for you to have a magnetic resonance imaging (MRI) scan to show the extent of the injury and any damage to the surrounding tissues.
How is ACL injury treated?
- Non-surgical treatment: involves physiotherapy and additional support – such as a knee brace – when playing sport. There are also ACL prevention programmes available that can help with rehabilitation and preventing further injuries
- Surgery: if your knee regularly gives way during normal everyday activities, or prevents you taking part in sport, your consultant may advise you to have ACL surgery.
Anterolateral ligament (ALL) injuries
The anterolateral ligament (ALL) runs along the outer part of the knee, providing stability when pivoting. ALL injuries – caused during twisting movements – affect around 30% of patients who have an anterior cruciate ligament (ACL) injury. Having ALL reconstruction surgery alongside ACL reconstruction, as part of the same procedure, significantly improves the long-term outcome.
Medial collateral ligament (MCL) injuries
One of the most commonly injured ligaments, the MCL provides stability to the inner (medial) part of the knee and feels tight when your leg is straight. It connects your thigh bone to the bone of the lower leg and stops the knee bending inwards. It’s often injured when the knee is knocked sideways and, in some cases, can be damaged alongside other ligaments in the knee.
Lateral collateral ligament (LCL) and posterolateral corner (PLC) injuries
The LCL and PLC stabilise the outer side of the knee and can be injured alongside other knee ligaments. The PLC is a collective name for a group of structures in the outer back corner of the knee. If damaged, as part of an acute injury, these structures can be repaired.
Multi-ligament knee injuries
When two or more ligaments are injured at the same time, this is known as a multi-ligament injury. In most cases there are also cartilage injuries or a meniscal tear, as well as knee instability. If you have a multi-ligament injury, there is also a greater risk of injury to the major blood vessels and nerves around your knee; this may mean you need to have multi-ligament surgery, which can involve more than one operation to stabilise the knee and prevent further damage.
What are the symptoms of of an MCL injury?
Symptoms include:
- A popping sound when you are injured
- Pain, tenderness and swelling on the inner knee
- Feeling as if the knee is going to give way
- Locking or catching in the knee joint
How is an MCL injury diagnosed?
Your consultant will discuss your symptoms with you and examine your knee to check for tenderness, stiffness, swelling and any difficulties with movement. He will also carry out a ‘Valgus’ test where he bends your knee and applies pressure to the outside of it. In most cases, he will arrange for you to have an X-ray to confirm the diagnosis. He will also arrange for you to have a magnetic resonance imaging (MRI) scan to show the extent of the injury and any damage to the surrounding area.
How is an MCL injury treated?
This depends on how badly the ligament has been damaged, and whether other ligaments are also affected. If you have only damaged the MCL, it is usually possible to treat it without surgery using a simple knee brace that holds the knee in a bent position for 4-6 weeks. However, if the tear is serious or other ligaments are affected, your consultant may advise you to have ligament surgery which can include direct repair with the internal brace technique or reconstruction of the ligament.
For acute injuries – and when there is a multi-ligament injury – Your consultant recommends the Internal Brace repair technique using fibre tape. This stabilises the joint and can enable you to begin light exercise within a week of surgery.
