Mr James Arbuthnot
MBChB, MRCS(Eng), FRCS(Tr and Orth)
Consultant Orthopaedic Surgeon
The anterior cruciate ligament (ACL) is a frequently injured structure, the estimated incidence of which is 0.81 injuries per 1000 per year. The injury frequently occurs in the sportsman or woman, often as a result of a non-contact twisting action to the knee during sport.
A rupture of the ligament can result in an unstable knee. This can frequently require surgery to stabilise it.
Surgery involves using a graft to reconstruct the damaged ligament. The graft is usually a tendon taken from the same knee, or alternatively a donor tendon can be used (an allograft).
Mechanism of Injury and Symptoms
Sports that are often associated with an ACL injury usually involve twisting on the loaded, partly bent knee. The main “risk sports” in the UK are: football, netball, skiing and rugby.
Women seem to be more at risk than men for sustaining this injury. This may be due to the shape of the female knee and hormone levels may also play a role.
Patients usually complain of a sensation of instability in the knee or of not being able to trust it, particularly when turning or twisting although they are often quite OK running in straight lines.
The level of symptoms can vary significantly from patient to patient: some people find that they can do pretty much what they want to do despite their injury whereas others are severely compromised by the knee being so unstable. Often the knee can become very sore, particularly after activity. Some patients have instability in the knee regularly during normal daily activities.
Wherever instability compromises the patient’s quality of life, there is a strong relative indication to have surgery to reconstruct the ligament. Even very occasional instability can profoundly affect a sportsperson’s confidence. There is also a good argument to stabilise any “loose knee” in order to reduce the risk of damaging the meniscal cartilages within the knee. This is because the meniscal cartilages have a hugely important role in protecting the knee from arthritis and there is good evidence that knees without functional anterior cruciate ligaments are at risk of developing meniscal tears.
At the time of injury to the ACL, other structures within the knee can also be damaged. As the knee is frequently unstable and gives way after the ACL has been ruptured there is a subsequent risk of injury to the knee whilst awaiting treatment. The structures most at risk are the menisci; the articular cartilage and the other ligaments around the knee.
A clinical assessment is needed by an experienced assessor. This may be your GP, your physiotherapist or your surgeon. This will include an interview giving you the chance to describe your injury and current symptoms and also a clinical examination. Tests to support this clinical assessment may often be required – an X-ray or MRI scan may be of benefit in further understanding your knee injury.
Do You Need Surgery?
A knee without a functional ACL is at risk of giving way. Episodes of giving way may stop you carrying out your normal activity. This may be accompanied by pain. When the knee gives way the articular cartilage and meniscal cartilages can be damaged. Damage to these structures can lead to early “wear and tear” arthritis in the knee. Preventing these “giving way” episodes is important – this can be through: avoiding “danger activities” (pivoting sports); rehabilitation; the use of a brace; or surgical reconstruction of the ligament.
The aim of ACL reconstruction is to give your knee more stability to prevent damage to the other structures in the knee and allow you a return to a higher level of activity than you can manage with the ACL-deficient knee.
The operation is usually carried out under general anaesthetic (with you asleep). It takes around 60 minutes to do. The knee is examined whilst you are asleep. A key-hole assessment of the knee is often carried out next to assess the ACL and other structures (such as the meniscal cartilages and articular cartilage). Injuries to these areas can be treated at that time.
The graft is then fixed in position. A number of different methods can be used to do this. The method shown is a “button” that is pulled up against the outer part of the femur bone and a screw inserted to the tibial bone.
Many surgeons use the hamstring graft from the patient as a first choice, but other frequently used grafts can be taken from the patient’s patella (knee-cap) tendon or the quadriceps tendon. Manufactured synthetic grafts can also be used. Another option is to use cadaveric (donated tendon from a deceased patient) tendons.
Each of these options has advantages and disadvantages. You should discuss the graft choice that your surgeon recommends.
Outcome of Surgery
80-90% of ACL reconstruction operations are successful enough to allow the patient back to the level of activity that they could undertake before their injury. The ability to return to sport depends on the delay from injury to surgery amongst other factors. The reconstructed ligament is not the same as having your own ACL. It is a replacement that is intended to give the knee stability. Having an ACL reconstruction does not mean that your knee is completely protected from arthritis. The main predictor for this would appear to be the amount of damage your knee sustained when the ACL was first injured.
Potential for Complications
Many surgeons undertake ACL reconstruction and thousands of such operations are carried out each year. Most surgeons have very few complications, but despite taking extreme care to minimise things going wrong, they occasionally do. Amongst the recognised complications of ACL reconstruction are the following:
- The knee might not have sufficient stability to allow the patient to return to sport/full normal activity
- The knee might still be painful. Pain at the front of the knee is known to be more common if the patella tendon is used as the graft, although the pain does seem to settle down with time
- Stiffness, particularly restriction of full extension of the knee
- Deep venous thrombosis (clot in the deep veins of the leg)
- Failure of the graft
- Excessive bleeding into the joint
The operation is normally quite sore and, although you will be allowed home the same day or one day after the operation, you will require painkillers for some time afterwards. A suggested post-operative schedule for the first few weeks is as follows:
- The wound should be reviewed by your district nurse or GP at 3 days post-op and then you should be seen at 10-14 days post-op by the surgeon when the stitches can be removed. You should keep the wound dry for 3 days minimum.
- Rest! You should keep the leg elevated as much as possible in the few days post-op to reduce the swelling. Using an ice pack intermittently can assist this.
- You should not drive a car for 3 weeks (as a minimum) and only start to do so when your physiotherapist has said that you are safe in this regard.
Stages of Recovery
The stages of recovery are as follows:
1: (weeks 0-2) – Gain full movement and allow the swelling to settle
2: (weeks 3-6) – Improve joint position sense (proprioception) and start muscle work with physiotherapy guidance. If the hamstring was used as a graft do not do resisted hamstring training until 6 weeks post-op
3: (weeks 7-16) – “Straight line” muscle training – i.e. no twisting, pivoting jogging. Introduce resisted hamstring exercises.
4: (weeks 17-26) – pivoting, cutting training can normally be introduced
5: (weeks 27 onwards) – gradual return to full contact sport.
DO NOT RETURN TO FULL SPORT IF:
– The movement in the knee is reduced
– The endurance or power of the muscles around the knee is reduced (i.e. the knee should have the same musculature as the uninjured side)
– There is still some swelling in the knee
– You are not “match-fit”
– Your physiotherapist or surgeon tell you not to.