Knee Instability (ACL Injuries)
Anterior Cruciate Ligament Injury and Treatment
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The anterior cruciate ligament (ACL) is one of the main restraining ligaments of the knee (see the diagram above). The ACL sits in the centre of your knee, running from the back of the femur (your thigh bone) to the front of the tibia (shin bone). Its role is to prevent excessive forward movement of the tibia. In practice, the ACL keeps your knee stable, especially when you twist, turn or side-step.
The ACL also provides important information to the muscles around the knee (proprioception), which help protect the knee during physical activities.
ACL injuries typically occur during a non-contact twisting movement. You may feel (or even hear) a ‘pop’. if you’re taking part in a sporting activity, you probably won’t be able to continue. Immediately after an ACL knee injury you may experience swelling as a result of bleeding into the knee. Other injuries to the knee can occur at the same time including meniscal tears (cartilage) or damage to the joint surface.
When you tear your ACL, you will probably find that the knee gives way, especially when you twist. If you also experience knee swelling, you are likely to be damaging the joint surface and/or meniscal cartilage. If damage to the knee continues, the eventual result will be osteoarthritis.
If you suffer an injury to the ACL you’ll find that your knee feels unstable, as though it is about to give way. You may also experience some swelling and knee pain. Typically, this will be most noticeable when you twist, however a small proportion of patients become so unstable that even simple activities may cause the knee to give way. Some patients can suffer an ACL injury yet still twist and pivot without the feelings of instability, although this is rare.
Yorkshire Knee Clinic’s specialists can usually diagnose a ruptured ACL from the history of the injury, confirmed with specific tests at the time of your examination. Diagnosis can be difficult in some cases (especially in the case of fresh knee injuries where examination may be too uncomfortable, or where the ACL damage is just one of a number of injuries to the knee). In these cases, we will usually confirm the diagnosis with an MRI scan as a torn ACL cannot be seen on x-ray.
Late diagnosis of ACL injuries is very common. Unfortunately, this can often mean the knee sustains further damage during the months (or even years) between initial injury and consultation. Such additional knee injuries can adversely affect the outcome of reconstructive surgery.
Surgery is required for most patients who wish to return to an active lifestyle following ACL damage, although some other non-operative treatments may be appropriate depending on your injury. Alternatively, you may choose to alter your lifestyle to avoid activities that make the knee give way (although for many, this is a worse option than orthopaedic surgery). If you opt for surgery, a period of physiotherapy prior to your operation is often recommended to help you regain normal movement.
A small proportion of patients are able to continue with their activities without major problems. These “copers” are typically (but not always) patients with lower physical activity levels, who do not participate in pivoting/twisting activities.
Non-surgical treatment of an ACL injury involves a supervised physiotherapy programme concentrating specifically on:
Functional knee braces are sometimes prescribed to help patients with damaged ACL’s. Their benefits are not fully understood although they may help with proprioception (see above). They are expensive and may not provide much in the way of support to knee stability.
Following an ACL rupture your Yorkshire Knee Clinic orthopaedic surgeon may recommend reconstruction. We will always discuss a recommended treatment with you, so you understand what is required and why.
ACL reconstruction is the commonest form of knee ligament reconstruction. The surgery aims to replace the stabilising function of the anterior cruciate ligament by removing the remains of the damaged ACL and replacing it with a graft.
A number of graft techniques can be used to replace the ACL. The two commonest graft techniques are to use two “hamstring tendons”, or a so-called BTB (bone tendon bone, or patella tendon graft). Medical literature suggests there is little or nothing to choose between these two graft-types in terms of results. Our knee surgeons tend to prefer hamstring grafts as a first choice.
In more unusual situations, your Yorkshire Knee Clinic consultant may recommend a different form of graft.
Our knee surgeons usually perform ACL reconstruction via keyhole surgery. We also make a small (4 to 5 cm) incision below the knee to harvest the tendons for the graft.
Your ACL reconstruction may be performed either as a day case or overnight surgery.
Provided you give your knee the right rehabilitation period (6-9 months) and follow our guidance, there is a 90 to 95% chance of a good outcome: that is, where stability is restored enough for you to undertake activities, including sports, that you were previously unable to.
Complications can include infection (in less than 1% of cases), nerve damage (a numb patch of skin, quite common over a small area, but rarely a problem), stiffness (uncommon) and failure of the graft due to re-injury or unexplained failure.
As with any area of health, treatment of ACL injuries develops and advances over time. Yorkshire Knee Clinic’s orthopaedic surgeons use only clinically-proven surgical techniques to give you the best possible outcome following surgery.