Anterior Cruciate Ligament Injury

A ligament is a structure that spans a joint from bone to bone to provide stability. The anterior cruciate ligament (ACL) is one of 4 major stabilisers of the knee joint and slightly unusually for a ligament, it is situated in the centre of the joint. It has a major role in providing support for knee rotational movements.

A tear of the anterior cruciate ligament is a significant and relatively common knee injury. It is significant in that it can unfortunately cause both short and long term issues with interference in normal knee function. There is no definite incidence data from Ireland, however, with extrapolation from international literature and population based studies, an estimation would be approximately 1 per 1500 people/year which could mean more than 3000 ACL injuries per year in Ireland.

The most common mechanism of injury is sport and in 65% of our cases here at SSC, this will not have involved contact. The typical history is a ‘pivot’ or ‘cut and turn’ move with a sensation of knee instability and buckling. Some individuals report a “pop” or hearing a crack from the joint. This invariably leads to acute pain and an inability to continue in the activity with the subsequent development of swelling. Not all injuries though are typical or sustained in sport with some sustained in higher energy trauma, a contact sports injury or in any uncontrolled rotational movement. Most individuals will immediately realise there has been a significant issue and then seek attention via their GP, A&E or physiotherapist.

The spectrum of injury pattern varies considerably and although it can be injured in isolation, an ACL tear can also involve damage to other knee structures such as meniscal cartilages, chondral joint surfaces, other ligaments and the actual bones themselves. For this reason, I would generally recommend an urgent MRI scan for individuals with a suspected ACL tear or who present from a sports pitch with a significantly painful and swollen joint. A straightforward plain X-Ray can be useful initially to rule out a major bone injury when an accurate full clinical assessment can still be difficult because of the pain and swelling.

The knee will then be sore to a variable degree for several weeks afterwards. Usually the acute pain and swelling gradually resolve and day to day normality can resume. Physiotherapy has an important role in this stage. This is mainly to instigate strength drills, restore range of motion and a normal walking pattern and to prepare for possible surgical treatment. This phase is termed “prehabilitation” and there is evidence to suggest it may improve overall outcomes and can make the early post-surgical recovery easier.

The main problem with an ACL injury is that unfortunately it has a poor inherent capacity to heal. This means that there is residual instability at the knee mainly in activities that involve rotation. Returning to demanding and pivoting sports can be difficult e.g. Gaelic Football, hurling/camogie, soccer and rugby. Certain individuals do seem to manage better and it depends often on the desired goals and age of the patient as to whether surgical intervention is necessary. Generally, the younger the patient and the more demanding the activity, the more likely it is that surgical reconstruction of the ACL will be warranted.

Not all individuals though need to consider surgery and the potential role of operative versus non-operative treatments will be discussed in detail at your consultation. Usually there is no need to urgently arrange surgery unless there are concurrent injuries that need rapid attention. These issues are generally accurately identifiable on an MRI scan.

Numerous studies support that our young patients in particular are vulnerable with an unstable knee and frequently struggle to have a meaningful return to demanding sports without surgical treatment and ACL reconstruction. Our data at SSC demonstrates that about a third of our reconstructions are on this vulnerable 12-20 year old age group. Evidence also suggests that without a stable knee, there is a higher rate of subsequent meniscal cartilage tearing and hence the potential for articular surface damage and the development of premature osteoarthritic problems in the knee. For these reasons, most young and active sporting individuals are therefore felt to benefit from ACL reconstructive surgery.

The surgical procedure of an ACL reconstruction is discussed here in more detail.

Follow this link for more information on the prehabilitation and rehabilitation programme

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