The ACL & Common Knee Injuries
Professor Cathal Moran

Watch this video of Professor Cathal Moran, Consultant Orthopaedic Surgeon at UPMC Sports Surgery Clinic, presenting on The ACL & Common Knee Injuries

This video was recorded as part of UPMC Sports Surgery Clinic’s Online Public Information Meeting, focusing on Knee and Sports Injuries

Professor Cathal Moran SSC

Professor Cathal Moran is a Consultant Orthopaedic Surgeon specialising in Knee and Shoulder Surgery at UPMC Sports Surgery Clinic.

This evening I’m going to speak to you a little bit about ACL injuries. I am not only going to be speaking about Anterior Cruciate Ligament injuries but I’m also going to show you a video of how ACL surgery is actually done.


The Anterior Cruciate Ligament (ACL) is one of the key ligaments of the knee. It’s the central stabilising ligament of the knee, here is a model. This bottom bone is the shinbone the area at the front is the knee cap or patella but if we look inside the knee we see a couple of key ligaments and the ACL is the one here in the middle of the knee which we find to be very important for athletes and players particularly those involved in what we call cutting sports which we have a lot of in Ireland like our GAA and field sports.

When a person goes to cut or turn or decelerate from a highspeed run that ligament kicks into action and provides a lot of stability through the knee. We know from injuries that very few athletes nowadays seem to be able to manage or cope to play when that injury occurs and we see it in all sports like rugby, hockey and GAA. What we do know is that it is primarily regarded as a non-contact injury. One doesn’t actually have to pick up a tackle or get hit for that to happen. It can simply happen by planting the leg going to cut and turn and classically the athlete or patient will describe the knee popping and giving way beneath them.

How does it happen? I suppose it happens in those field sports by cutting and turning the knee buckles and gives way and often the player or the players around them will hear a pop and they will suddenly see the players collapse to the ground. There are times a player might get up and try go again but unfortunately it often doesn’t allow it.

In terms of early assessment, the athlete will often try and get up and get going on the field of play again but classically it will give out and that is a key first sign.

Swelling is very typical in the early stages following these injuries certainly in the first 24 hours and often even in shorter periods and there are only a few things that can cause the severity of swelling that the ACL injury is associated with.

Nowadays, thankfully, most teams have physiotherapists be it on the field or a follow up of an incident where they can get assessed and rapid access and history gives the game away as to what has actually happened and from there one would typically come onto a specialist in sports surgery for assessment like our own and we use a number of evaluations. We go back over the story, we do take the history again, we will examine the knee and that means we can see the knee when it is evaluated that there is a certain amount of instability. We can see for example a Tibia in a torn ACL will slide forward a little more when we evaluate it and that is what we call the Lachman test. The next thing we typically go onto do then is use an MRI scan and the MRI scan is usually the icing on the cake and it gives us all some final information as to what might have happened.

In addition to confirming that the ACL is probably torn we can also see some other clues like a pattern in bone bruising where we see bruising within the thighbone and the shinbone which often documents the mechanism of injury which would haver happened.

Other ways a torn ACL can happen is through hyperextension or there are some other more unusual ways but the most common is what we call the pivot shift.

That now brings us to the athlete with the torn ACL and where we go from there and as I’ve said we do know that up in 20% of GAA injuries are ACL injuries at this stage.

In a country so interested in field sports there is a lot of interest in getting these athletes back to play. There’s often some debate about whether athletes can cope with an ACL injury and may not need surgery and they are the type of things we discuss here in the practice with you when you come along to discuss the ACL.

There are certain patients who are involved in sports like cycling and swimming who may get away without ACL reconstruction but for the vast majority for the ages between 15-25 playing a lot of field sports that the ACL does need to be reconstructed. A lot of work needs to be done before we actually get to the ACL reconstruction phase. The first thing we do following any knee injury is to realise that its not just an ACL injury but it is an injury to the whole knee as we get soft tissue damage of the entire knee and we get a fear of movement and in the early stages we go down the line of what we call prehabilitation or recovery of the knee essentially after injury. This classically is something we would do with the help of your treating physiotherapist from home. We can work with it we have our own internal team of clinical specialists here in the practice both in a Sports Medicine and nursing background and also a physiotherapy and rehabilitation practice but we also look to work with physiotherapists and specialists all around the country and we find that that form of communication always gives the best results we can and in the early phases the first thing is to diagnose the injury and reassure the athlete and reassure the parents if they are in the picture as to the nature of the injury and what we might do about it.

What about the preparing for surgery phase? I suppose it is really about getting normal homeostasis by getting the knee back to normal and that is done by getting the swelling down, returning the knee towards normal movement, really ensuring full range movement if we can and so on.

The other thing we like to do in the early stages is to do an MRI scan to try and identify any comorbid injuries whether there is any damage to the cartilage the lining of the knee joint. Whether there is any lining or damage to the meniscal soft tissues the little wedges that act as shock absorbers within the knee. They are what is known as prognostic indicators as they can influence how well the knee will do over time. They can also influence whether we need to intervene rather urgently or if it is something that we should wait a few weeks for before intervening. Sometimes where there is a large tear of a meniscus we call it a bucket handle tear and if an athlete has this they will need to go a little earlier to surgery to get that settled down. We like to give anywhere between 4-6 weeks in the early stages to get the knee settled, get the swelling settled and then get the knee ready for surgery. The next step, just to explain to you how surgery typically happens is when a surgical procedure is required for an ACL reconstructive surgery in my hands it is typically done doing a one night overnight stay in the hospital and as the athlete or patient they would typically come in the day of surgery and stay the night.

What I’m going to do now is take you through a video of how I do an ACL surgery and it is a small animation just so you can understand. Ill speak a little bit about graft choices as I do and take it from there.

Now, we are looking at an animation of a knee and here is the ACL in the middle of the knee which is the key ligament that gets torn and we need to reconstruct.

To the side we have 3 of what we would call graft options. In the middle we have what is my preferred graft choice known as the patellar tendon graft and it is my preferred choice because at the end we have bony attachments and these will integrate well into the tunnels which I will create.

Another option we have is known as the hamstring graft which e use on occasion and also a quads tendon graft. These grafts are used to reconstruct the ACL as need be.

When we are undertaking a procedure the first thing we do is actually obtain the graft and as I mentioned the patellar tendon is my preferred graft of choice and where you see it coming from is here at the front of the knee at the knee cap.

This is the tibia and essentially, we harvest an area of about 70-80 millimetres in length and this essentially will be used for the ACL graft at the end of the day.

One of the first things I do when I’m doing the ACL reconstruction is go into the knee with a camera and shaver to remove the old torn ACL.

The next step then is to drill little tunnels into the shinbone and into the thigh bone and its through this area that the new ACL graft will be placed we do this again all in a keyhole manner, keyhole technique.

Here you will see it being pulled into the knee with what we call our guide wire which puts our graft into place. It is now that the ACL reconstruction is being undertaken.

The last aspect of the surgery that is key is the fixing in place of the new ACL with screws and that is really it, that is our new ACL in place and once this is done we essentially bring the patient back to the ward and allow them some rest and commence rehabilitation.

That is the key aspect of ACL reconstruction by the use of a patellar tendon graft and that’s the whole story really.

Firstly, we have the diagnosis, then we have our rehabilitation then we move into what is known as our post op rehabilitation phase. I suppose the first thing an athlete needs to know is they typically will be using crutches for two or three weeks following the procedure to allow the healing to start and I suppose the emphasis on the post-operative phase is to ensure we are working with our own clinical team and indeed other clinical teams around the country, getting the knee back to it’s full range of movement, getting the swelling down and getting the athlete or patient moving in order to be comfortable again.

Once we get early movement going on in the first 6-8 weeks we move into something that is known as the strength phase and that involves building up the strength in the quads and building up the core to essentially move this over the following 3-4 months towards the knee and the limb will then be strong enough to start a return to play programme.

There really is a multidisciplinary approach to this obviously a lot of it is based around physiotherapy early on then we have strength and conditioning and we follow specialist guidelines in this regard but there are other key aspects that are very important and these are often neglected and we see many athletes report of this as this often involves proper nutrition, proper hydration, proper sleep and I suppose being able to maintain the proper motivation and the psychological support that go with being able to keep your training going often in isolation, often over winter periods where the teams are playing away.

These are key aspects as to why we would have regular follow ups with the athletes and patients over the few months that follow, giving feedback to their physiotherapists, to their families and so on these are all key aspects of doing well in the long run.

It is not solely a time dependant manner but it takes anywhere in the region of 8, 9 or 10 months and sometimes even longer not just to rehabilitate but to bring that athlete back to a level where they will eventually be able to return to sport.

We do that and then eventually we do something that we call biomechanical testing and isokinetic testing where we get some measures at our Sports Medicine centre here at UPMC Sports Surgery Clinic and that allows us to guide the athlete further. Some of it is clinical and part of it is what we feel and see the athlete doing but there are also some objective measures that we use.

Eventually, at the end of the period together we will decide in relation to turning the athlete back to play. I suppose the one thing to think about is that when the return to play period comes that has to be handled very carefully, we know that fatigue can set in very early in athletes towards the end of their programmes and it is important that they gradually build up their time that they are able to do their cutting and that they are able to do their basic activities in a non-contact manner before they went to full contact and even when they get back to full contact and build up their play maybe 20 minutes at a time then they don’t just launch into full scale games because that would probably just increase the risk of re-injury so that’s really just the classical stuff around ACL care and there are some key points that I would like to make because I suppose there high risk groups that you will see us taking particular care with we know for example the rate of ACL injuries in females is much higher than males I think part of that has to do with the way the body and the knees are set up but we also think there might be some flexibility or hormonal issues that play a role so we take particular care around certain athletes to ensure they are given the proper support.

The other group we would like to discuss are our youngest athletes because we know if you have an ACL injury under 16 years of age your chances of having another substantial knee injury or ACL injury in that same or other knee might be as high as 20-25% so it is very important that they get treated, assessed and guided back towards a proper rehabilitation programme and that we take our time in getting them back to play.

That brings us back to the bigger question of ACL prevention and thankfully nowadays there is an increasing interest around this. The GAA have programmes and FIFA have programmes out there where what is most important particularly at a local level with athletes of all ages in addition to playing are putting some time into basic strength and conditioning to gain some basic flexibility there is a tendency nowadays to be playing a lot but perhaps with some emphasis on background training and background warmups and one of the key things I would like you to take from this talk this evening is that this is key to preventing our athletes from injury to the ACL and indeed injuring many other structures as well.

What about research then? There is a lot of clinical research going on here at UPMC Sports Surgery Clinic going into not just why these injuries are happening but optimising our rehabilitation programmes, how we can get athletes not just back to the game but back to staying in the game that is probably the most important thing of all and we are constantly doing research as to how we can get our rehabilitation programme better and see what other factors we can address. These are all small increments to get our athletes back safely in the game.

Other research we do is that I’m working with a group in Trinity College Dublin and were doing some bioengineering research where we are looking at how we can out mend ACL healing where we don’t actually have to replace or reconstruct all ACL’s for some it is actually possible for it to heal and we need to look at them groups where it might be possible and how it might be possible with synthetic grafts.

The last thing then I’m going to address is something people might be concerned on and it is the long-term effects. When you have any substantial injury to a knee joint or to any other joint of the body we do recognise nowadays that there can be long lasting effects and the one many people worry about and know about is called post traumatic osteoarthritis or wear and tear over time.

We do know that 20-25% of athletes that do have an ACL injury might need another surgery on their knee over the next 7-10 years and it is not a major surgery it is usually just a little keyhole surgery to clean out scar tissue or damaged cartilage or damaged meniscal tissue. Often the ACL is the start of some issues in the knee and I suppose that is why you need to have it cared for under specialist care in specialist hospitals and it is important so you can get the correct diagnosis early on and if little niggles do arrive then we can help you address them.


In truth, I would have to make the declaration that there are no true stem cells available in orthopaedics outside of clinical trials.

Unfortunately, there are a lot of false suggestions made by clinicians that they have stem cells available for use and they are not really, they are mixtures of stem cells from the body but true stem cells are not available for use.

Evidence would suggest that there is some role for them in reducing inflammation there has been no proven benefit as of yet that they can actually prove or manage regeneration so really it is just another pain modulator.

It is important though that when patients do go down the line of using stem cells or speaking to people about them that they are properly consented in the centre where they are properly informed.

Menisci are some of the key structures internally in the knee we regard them as playing a role in shock absorption and weight distribution.

I think as such they are naturally going to wear out over life so when we get into our 40’s, 50’s 60’s and so on if we have an MRI of the knee then your knee will show some form of a meniscal tear a so on.

The vast majority can be treated with the out surgery they can be treated literally with exercise, movement and so on. There are times though when we have to go into the knee and clear out the damaged tissue as it may be causing mechanical problems or it is not responding to exercise but the key thing I would say to most patients would be to keep moving and keep exercising.

The last thing I suppose is to know that there are some meniscal tears that can be acute large meniscal tears in our younger athletes and they are often something we should give an opinion on and have a discussion with the athlete about whether or not we would intervene some can be repaired and some not but that is when an opinion should be sought.

It is like the stem cell question, there is no real evidence that plasma should be used instead of a cortisone injection.

I think what they really need is a proper assessment with a high qualified sports med physician or an orthopaedic surgeon sometimes the pain can be arising from elsewhere like cartilage and underlying bone damage it is often tempting to think on the MRI reports that the meniscal tear is creating the issue but it really goes back to a proper clinical assessment.

I think firstly it goes back to the proper clinical assessment as to what is going on. Knee support is fine but really people with knee pain should be on a proper physiotherapy or strength and conditioning programme and wearing a support if you are not doing the background work probably is not the way to go, they don’t do any harm but again in a properly cared for environment a proper assessment is what you should get but they can play a role.

It can but I think what is tempting to think about is always the meniscal tear and the surgery and so on.

I think what people might be best focusing on is a more wholesome approach to their overall health looking at their weight, looking at their movement, looking at their activity level and keeping themselves strong. I think those factors play an as big if not bigger role than simply a discrete meniscal tear and meniscal tissue loss.

While it is true to say that there is probably an increase in association with meniscal loss and arthritic change I think it would be important to keep in mind that specialist surgeons and sports surgeons would be well aware of not removing tissue but just the damaged tissue and hopefully facilitating an increase in movement and function that should keep the athlete healthier overall.

I think it is. I think that goes back to having proper expectations, proper counselling I think it is something we often take our patients through, there are many different types of meniscal tears, cartilage damage and so on. It is not just simply whether or not you have a meniscal tear but it is the pattern of the tear, the location, what the underlying cartilage is like and then it goes back to running but I suppose when we talk about running it comes down to the frequency, the intensity, whether or not there are breaks involved and maybe a mix of sports like cycling or swimming often help as well.

Certainly, the overall message would be that you can remain fit and active even after having these little injuries and we would often encourage proper supports to be done.

I think whenever anybody has any type of acute knee injury that we need to get the proper programme in place and a lot of it often requires elevation and icing with some movement.

A well-qualified physiotherapist really should be able to identify a knee that is very unstable that means not just a knee that has an ACL tear but a PCL tear a lateral tear.

Some of these knees might benefit from a little support from the brace for the first few days before they go and see a specialist about it.

I would generally say a bigger fear we have though is of people getting stiff often the past patients that have not been assessed would maybe be locked up in braces and not having proper access to physicians and that stiffness can often be an undoing or at least a delay in treatment.

Similarly, afterwards, I would have worked in centres, I would have seen it documented internationally people are using braces. I suppose people that work with me would be very aware that I would be pro getting it fixed properly not as such anti-bracing but I think getting that knee moving certainly works better and I think that is the ideal way to go.

Just moving away from ACL’s alone in isolation. I think it is well accepted at the moment that we have a couple of problems brewing.

On one hand we have a group of children in certain parts of our country that maybe are not moving enough by looking at obesity epidemics to diabetes and so on. Another area then is the opposite where kids are going game to game, sport to sport and probably not doing enough strength and conditioning and I’m not talking about being in the gym lifting weights but proper warm ups maybe at least acknowledge that they need to do a strength and conditioning programme once or twice a week there’s GAA and Rugby teams u12 and u14 training young lads training 3-4 times a week playing matches on the weekend relentlessly the year round and I have to say I’m not quite sure that is the way to go I have children myself and they are very active in sport but I do think it is important to keep the balance between training as well as playing I think that is more important.

I think footwear could play a role but I think one of the great things we see nowadays is that there are many more females partaking in sport and not just participating but being supported to participate at multiple levels in multiple schools.

Again, though one of the biggest things we need to see is to keep introducing the importance of strength and conditioning to those programmes and not just playing because its not just playing sports but it is about being in sport. There can be huge dropout rates following injury and I think doing that in the background is more important for a child or a teenager to have a game and a training session maybe a couple of sessions instead of just playing all the time and it is not just ACL injuries because we see a lot of over use injuries, some back problems, through to knee problems and again it just needs to be proper warm-ups proper strength and conditioning ad playing.

I suppose with the baker’s cyst has it been diagnosed clinically or with an MRI as it can be tempting I suppose sometimes to assume that is the cause of the pain but essentially first of all a baker’s cyst is a collection of fluid at the back of the knee and what happens is a knee is probably producing excess fluid because of the excess inflammation over the wear and tear and so on. The fluid sneaks out through a little crack in the cartilage and in the meniscal lining and it builds up because it acts as a one way valve so its fine maybe about taking the fluid out of the back of the knee with aspirating which means sucking it out of the back of the knee but unless you deal with the internal problem it will just be like any other problem and just come back.

It is important to know that it is not a growth and it is not a legion or cancer or anything like that. It is a collection of fluid and if it is bothersome consider what might be causing it and if it is not just leave it alone.

In the best of conditions at a young age even with healthy tissue and so on, being able to undertake the repair of a meniscus is often unlikely that it will heal so the person assessing it should have the skillset to decide whether or not it would be likely to heal so an inappropriate repair has been undertaken just pre-disposing the patient to another surgery.

Secondly, as I said earlier on when we are in our 40’s, 50’s and 60’s our meniscal tissue does become a little worn out certainly very few people who have meniscal tears go on to having a joint replacement which is an extreme endpoint for end stage arthritis. You might lose some rotation in your knees as the years go on but you should keep your weight in order and keep fit and active they can often be factors that keep things at bay.

Yes, Partial Knee Replacements are possible and Total Knee Replacements are too but that is for end stage arthritis so that is a whole different level of symptoms than a meniscal tear might be causing.

There are but again it would take a proper assessment because we need to go into what might be causing it you think with patellar tendinopathy’s it would be overloading mechanics and altered hip mechanics we would often think about the knee but we would go back to the body down through the quads down to your shins through the back to the hamstrings and so on.

Looking at the balance there, looking at the movement maybe figuring out why the patella is overloaded that is really driving the pain so rather than the different exercises you can do.

Again, it is possible to work through it with physiotherapy but first of all to diagnose what might be driving it.

For further information on Anterior Cruciate Ligament (ACL) Reconstruction, please contact
Date: 15th November 2023
Location: Online
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