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Do I need an Anterior Cruciate Ligament (ACL) reconstruction?

January 16, 2019

And if so what, who and when…


An Anterior Cruciate Ligament (ACL) reconstruction is a major operation on the knee in which a torn/ruptured ACL is replaced by other tissue, usually tendons from another area close to the knee. ACL rupture is a common injury and is thought to occur in approximately 52,000 patients in the UK annually. The injury typically occurs whilst twisting/pivoting on the leg when playing various sports such as football, rugby, skiing and netball.



Knee stability is not simply due to the presence or otherwise of an intact ACL. The knee joint is stabilised by several factors which all work together in a unique way for each individual:

  • The shape of the bones in the knee joint is important especially the natural slope of the top of the shin bone (tibia)

  • The other knee ligaments, in particular the collateral (side) ligaments play a crucial role and may also be damaged at the time of ACL rupture and require attention

  • The mobile cartilages (menisci) inside the joint and their attachments to the capsule of the knee (especially the inner, medial meniscus) contribute a lot to stability. For this reason, your surgeon may undertake a repair of a torn meniscus at the same time as the ACL reconstruction


  • The strength of your ‘core’ muscles and the large muscles on the front (quadriceps) and back (hamstrings) of the thigh are hugely important. The restoration of normal and symmetrical strength is a corner stone of preparation for and rehabilitation from such surgery

  • Lastly the patients’ muscular control and coordination (called ‘proprioception’). This is often better developed in some individuals than others and is significantly affected at the time of the injury

ACL reconstruction is a stabilising operation and it is not usually performed because of pain. Data from large National Registries (databases) show that about half of all patients with the injury undergo a surgical reconstruction (26,000 patients a year in the UK). Nobody must have an ACL reconstruction, however certain individuals will experience recurrent giving ways episodes if they make a return to ‘pivoting sports’ e.g. football, rugby, hockey or netball. This is particularly so for the younger age groups.


So; the operation should be undertaken in individuals who have an either have an ongoing unstable knee or those more active, sporting individuals who want to play ‘pivoting sport’ but lack the confidence and perhaps have a fear of further instability episodes. There are exceptions to all ‘rules’ of course but generally the younger and more active you are, the more likely it is that you will require a reconstruction.


There are though some patients who have sustained an ACL rupture and - following an extensive strengthening and rehabilitation programme - are able to return to sport without an ACL reconstruction. We do not fully understand how or why these patients are ‘different’.


One of the problems is that knee laxity – how much a surgeon can move the knee – does not necessarily match the patient’s feelings of instability. The decision to operate therefore is solely based on symptoms.


There does seem to be a familial connection with large numbers of parents who have previous had such an injury attending the clinic with their son or daughter (as I did!). Once again whether the connection is the strength of the ligament, the strength of the attachment, the shape of the bones, muscle strength and coordination … is not yet clear.

Every giving way episode is a powerful, atypical movement of the joint which can result in injuries to other structures in and around the joint – the articular cartilage on the surface of the bone, the meniscus within the joint or other ligaments within or around the joint.


If such instability events continue it would seem logical that early arthritis (wear and tear) might be expected to develop after a few years. In reality, a number (30/40%) of ‘ACL rupture’ patients do sustain some arthritis but this doesn’t seem to be related to whether or not surgery is undertaken. Despite the best efforts of both surgeon, physiotherapist and patient osteoarthritis can still occur.



The most up-to-date research is looking at modifying the inflammation which occurs within the joint at the time of the injury / surgery to try to reduce the damage to the joint cartilage which can occur as a result of the (inflammatory) chemicals which are released at the time.


When do I need ACL reconstruction?

This is not an emergency operation and no harm comes from waiting, as long as the knee is not frequently giving way which can cause more damage to the structures within the joint: specifically the menisci (mobile cartilages) and joint surfaces. There are some associated conditions that may require more immediate surgical attention such as when a significant tear of the meniscus has ‘flipped’ into the middle of the joint and is blocking full movement. In addition meniscal tears and damage to the joint surface can be easier and more successfully repaired if early surgery is undertaken which is more relevant to the younger patient. There are also some surgeons who are trialling newer techniques to repair the ACL tissue back to the bone and if indicated (usually on age) this ideally requires surgery as soon as is reasonably possible.


Who should I see for my surgery?

Like most surgical procedures better outcomes are seen with those surgeons doing a high number of these particular operations. There has been no research done to come up with such a figure but it would not be unreasonable to want your surgeon to be doing one of these procedures every week or two (at least 20 a year). The National Ligament Registry (NLR) www.uknlr.co.uk is a UK Registry of knee ligament surgery which was established in 2013 by a group of surgeons including Sean O’Leary. This is a voluntary audit tool for knee surgeons to collect operative and outcome data on their ACL reconstruction patients and in doing so they can continually review their own results and compare to the national average. A map of those surgeons who have engaged in this process is available on the NLR website.


What sort of material will be used for my graft?

There are a variety of options for the graft material:

  • A bit of ‘you’ (Autograft)

This is usually either a strip of the tendon from the front of the knee or a couple of the hamstring tendons from the back of the knee. This is the most common option used in the UK.


  • A bit of ‘someone else’ / donor graft (Allograft)

This is more commonly used if you have undergone previous surgery and the tendons have already been used. An allograft is sometimes required if you require surgery to more than one ligament. The graft will have undergone a sterilisation process to significantly reduce the chances of any disease transmission although in doing so in the past this has lead to a higher re rupture rate


  • A bit of animal tendon, not human (Xenograft)

There are some ongoing experiments looking into such grafts but they are not currently available


  • A synthetic graft

Although seen by some as an attractive option – no graft harvest required, no pain or weakness from the harvest site, good early fixation allows for aggressive rehabilitation – synthetic material inside a joint does fret and fray over time. The particulate matter which is generated causes inflammation to the joint (pain and swelling) and there are several reports of subsequent bone cysts and joint surface damage. This remains a serious concern as we continue the search for the perfect graft.


Strength and rehabilitation

A supervised and structured rehabilitation programme is crucial to the success of any reconstruction surgery. It underlies the successful return of the patient to sport and the (hopeful) prevention of future injury. This programme will be based on patient function and rehabilitation ‘achievements’ rather than on time frames and is best undertaken by physiotherapists who work closely with your surgeon and are in regular communication.

One of the cornerstones of a successful rehabilitation programme is strength and this may even be overseen by a qualified strength and conditioning coach. Successful return to sport typically takes 9-12 months but may take longer in certain patients especially if there have been other associate injuries.


Am I repaired for good after my surgery?

Occasionally and despite good surgery and dedication to your rehabilitation programme, re injury does occur; especially in the younger age groups. This may be either a rupture of the graft in the same leg or a rupture of the native ACL in the opposite knee. This can affect >20% of teenage patients in the first two years following surgery and it is something the surgeons and physios are working hard to understand.

When any patient is making a decision about surgery it must be made with access to unbiased information about both short term function and all of the potential longer term issues. At the present time all we can do is what we know to be best and keep looking to improve …


Sean O’Leary