The Cruciate Ligaments of The Knee

Hello and welcome back to the ThreeSpires Physiotherapy blog where we take a look at all things physiotherapy and health related. Over the last three blog posts we have been taking a deep dive into the mysteries and wonders of the knee, its anatomy and sources of potential injuries. So, I thought that in this blog we could carry on looking at the knee but move onto two of the vital ligaments of the internal structure of the knee which are impossible to see but are often injured and which most people will have heard of at least one: the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). One point to note is that the optimal treatment for an injured anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) is a matter of current research and debate and as such although I will try to cover the best treatment options you may read different opinions elsewhere.

As always when discussing structures such as the ligaments of the knee and in this case the internal ligaments it is important to have a good understanding of what the structure is, the anatomy and where it can be found before considering specific injuries and rehab. So I think firstly we should now have a look at what the internal ligaments in the knee actually are:

The Cruciate Ligaments of the Knee: ACL & PCL

anterior cruciate ligament ruptureThere are two cruciate ligaments inside the knee joint: the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), they are both extremely important in terms of stability of the knee and generally if one of your cruciate ligaments is ruptured you will know immediately and there may be a loud pop. As you can see from the image they cross each other inside of the knee joint and this is the reason for their being called cruciate. It is worth having a brief look at each of the cruciate ligaments in turn.

The Anterior Cruciate Ligament (ACL)

The anterior cruciate ligament (ACL) is runs from the front part of the plateau of the tibia to the back part of the femur and it also on its way has some connections with the latera meniscus. As with all ligaments it is non-contractile meaning it is not connected to a muscle and does not actively pull on anything. Instead the anterior cruciate ligament is a passive restraining structure and we will look at its role in detail a bit later.

The Posterior Cruciate Ligament (PCL)

The posterior cruciate ligament (PCL) runs in the opposite direction to the anterior cruciate ligament (ACL) and goes down from the medial femoral condyle to the back part of the tibial plateau. The PCL is stronger and shorter than its cousin the ACL which results in it being less commonly injured.

The ACL is by far the most commonly injured and is the most common mechanism is by jumping, then landing and trying to change direction quickly - as is often done by players of many ball sports such as football, hockey and netball. The PCL is much less commonly injured and it will generally involve the shin being trapped or stopped from moving forward as the femur moves over the top.


What is the role of the Anterior Cruciate Ligament (ACL) ?

As discussed in our last blog on knee ligaments it is worth remembering that ligaments are passive structures and do not pull actively as they are not attached to any muscles. The anterior cruciate ligament (ACL) because of its position deep in the knee running up from the tibia to the femur mainly resists the tibia from moving forward underneath the femur and provides general stability for the knee joint.

What is the role of the Posterior Cruciate Ligament (PCL)?

The posterior cruciate ligament (PCL) runs in the opposite direction from its cousin the ACL and therefore provides a different resistance and restraint to movement of the knee. As it runs down from the femur anteriorly (at the front) to the tibia it limits the amount that the tibia can move backwards underneath the femur. As with the anterior cruciate ligament (ACL) it also provides some general stability for the knee joint.

What are the Symptoms of a Cruciate Ligament Injury?

Usually the symptoms of a cruciate ligament injury are very easy to pick up. There will almost always have been an incident where the patient can clearly remember something happening to their knee and a lot of pain afterwards. Most commonly this will be when they twist and turn in a football game and they will have been unable to walk afterwards. Despite the differences in the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) it is very unlikely that either will rupture or tear without a significant event or easily rememberable mechanism. After the initial injury the knee is likely to be very swollen and the patient will be unable to weight-bear through it for several days. Also even though things will improve over the following days and weeks the patient will generally describe a feeling of instability in their knee that even when the pain has subsided means that they don’t feel that they can trust their knee. Sometimes their knee will give way completely and they will go to the ground.

What Causes Cruciate Ligament Tears or Injuries?

Given the differences in the position and structure of the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL) it is probably best to consider what causes injuries to both slightly separately as injuries to the posterior cruciate ligament (PCL) are much rarer.

Causes of Anterior Cruciate Ligament (ACL) Injuries

acl injury footballAlmost always there is some trauma or “an event” that the patient can remember when they think that they hurt their knee. Generally, it will be quite a clearly defined event such as playing football and they will have twisted and tried to turn often while running and there will have been an immediate and very sharp pain inside their knee. Immediately they will have been unable to weight-bear and it will be obvious that something is wrong. Below are some common causes or situations in which anterior cruciate ligament injuries occur:

  1. A twisting and rotational force at the knee. Mostly this will happen in a sporting environment such as game of netball or hockey. Often the player will be moving quickly or have jumped and will be trying to twist and turn. Sometimes they will hear an audible pop as the injury occurs.
  2. Bad Landing: here the patient has done some form of large jump. Tis could be in a sport such as long jump or skiing or may simply be that they were having fun and running and jumping. Again they will almost certainly immediately know that they have injured their knee and will most likely be unable to weight-bear.

I think the main point to note from the above is that usually there is some form of rotational movement at the knee and that the patient will almost certainly know that they have hurt their knee and will be unable to weight-bear through it.

Causes of Posterior Cruciate Ligament (PCL) Injuries

So, although in theory all of the above ways of injuring your ACL could also injure your PCL in reality the posterior cruciate ligament (PCL) is much stronger and thicker than the anterior cruciate ligament and tears much less frequently. Mostly an injury to the posterior cruciate ligament will require trauma and the tibia to receive an impact that moves it backwards underneath the femur. This can happen in a road traffic incident or aggressive tackle where the player’s foot hits the shin and stops the other player moving and the femur keeps on moving forwards. Again, almost certainly the person will know that they are injured and there will be pain and swelling.

Who is at Risk of a Cruciate Ligament Injury?

Well, obviously if you have a knee then you could in theory injure your cruciate ligament. However there are some factors that make injuring either your anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) more likely.

  • Anyone involved in a sport or activity that involves jumping, landing, turning and twisting at speed. Sports such as football, netball, basketball, hockey and rugby all involve this kind of motion and have a risk of cruciate ligament injuries as a result.
  • Weight: people with a high BMI can often overload their collateral knee ligaments.
  • Anyone starting a new sport involving running, sprinting or twisting etc. In the early days of beginning a new sport your knee ligaments are likely to be exposed to stresses that they are not accustomed to and can get injured as a result.

How is a Cruciate Ligament Injury Diagnosed?

physiotherapy assessment knee injuryThis will in general depend upon the severity of the initial symptoms and where the injury took place for example on a football field. Most commonly though an injury to either the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) will be initially diagnosed or at least highly suspected by a physiotherapist.  This diagnosis will be made through a combination of symptoms and a physical assessment by a physiotherapist and usually a referral will be made for the patient to have an MRI in order to confirm the diagnosis and see if any other structures such as the meniscus have been damaged.  Sometimes patients will initially go to A&E with severe knee pain or they may attend their GP with knee pain in both cases they will often be referred onto physiotherapy for further assessment. The physio at this point will take a full history, do a physical assessment and based on the combination of these factors make a diagnosis of either an anterior cruciate ligament injury (ACL) or a posterior cruciate ligament (PCL) injury. As with most sporting injuries It is best to get an early diagnosis of a cruciate ligament injury as this allows the best management and treatment plan to be devised and for you to get back to your activity as soon as possible.

Treatment for Cruciate Ligament Injuries

As mentioned at the beginning of this blog the optimal treatment for a cruciate ligament injury such as an ACL tear or a PCL tear is a matter of current research and will depend upon a number of factors such as the age of the patient, what they wish to get back to doing and how difficult that would be for their knee. This is by no means a straightforward decision and will involve discussion with the patient about the lengthy rehab period after surgery and also potential limitations if the patient wishes to avoid surgery. As I said, not an easy decision! Below I have attempted to discuss in some detail each of the main treatment options: surgery and conservative management/physiotherapy.

So, before looking at these options it is worth first considering the fact that most important thing that you can do is firstly get an early assessment and diagnosis of either your anterior cruciate ligament (ACL) injury or your posterior cruciate ligament (PCL) injury. Yes, I know this sounds like me offering a bit of common sense advice but in reality this is the most important thing you can initially do to help with knowing how to best manage your cruciate ligament injury. You need to know exactly what the issue is and get some advice on what to do next. By having an early assessment and getting a clear diagnosis you can be confident about what you are dealing with and then choose the best treatment options.

Okay, I think we now need to take a look at the two major options for treating cruciate ligament injuries.

Physiotherapy or Surgery for Cruciate Ligament Injuries

physiotherapy for cruciate ligament injuryI think it is beyond the scope of this article to conduct a full literature review of the pros and cons of physiotherapy versus surgery for ACL and PCL ruptures and even if we did so there would not be a clear answer. Instead I think it is best to discuss some of the key points regarding whether you should opt for physiotherapy or surgery if you have had an anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) injury. In the past there would not really have been much discussion with patients about whether or not they needed surgery as it was thought that their knee would not be able to cope without either of their cruciate ligaments and they would simply be referred for surgery. However, over the years evidence has come to light that shows that some people can cope well without their ACL or PCL (even some high level sports people) and that it is important to consider a range of factors and ensure that the patient is fully informed and can participate in decision making as to which will be the best option for them. So, what are the factors that you should consider when thinking about the best treatment option for a ruptured cruciate ligament?

Length of time of recovery: the rehab  process following a cruciate ligament reconstruction is extremely lengthy (approximately 9 months) with a significant part of that recovery either being non-weight bearing (on crutches) or only using very low loads. For many people this period of time will be the deciding factor in whether they choose to try physiotherapy at least initially to see if they can strengthen their knee enough to cope with the loss of the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL).

surgery for anterior cruciate ligamentPatient Goals: the activity that the patient wants to return to and their personal goals often dictate what is thought to be best. A young sporting individual who is desperate to get back to basketball or netball may well feel that surgery offers the most likely guarantee of recovery and they will be willing to take on a lengthy rehab process. For other patients they may simply want to have a pain free knee that can cope with running, jogging and walking and they are willing to wait and see if their knee can cope with the lack of a cruciate ligament.

Age: I think it is fair to say that age really will play a significant role in decision making here in terms of recovery, ability to take time off work and desire to get back to a chosen sport. A young patient, physically fit and with a good background in sport who is desperate to guarantee that they can get back to their chosen sport as soon as possible is going to be well advised to consider surgery. Whereas a much older patient (say in their 60s) who has fallen and torn their anterior cruciate ligament (ACL) and for whom there is no desperate desire to get back to high level sport may well feel that surgery is not the best option and that they would rather wait and see if they are able to strengthen their knee to a point where they can cope with the loss of the cruciate ligament. Clearly, there are a range of ages and situations in between the two extremes that I have portrayed here and certainly a patient in their 40s, who is unable to take large periods of time off work but is involved in high level sport at a masters level will have a very difficult decision to make.

How well the knee is already coping: outside of the world of professional sport most patients who are likely to have an ACL or PCL reconstruction will be at least (and most likely much longer) 6 – 8 weeks since the initial injury. By this time some people will be already coping well without their cruciate ligament and it will be clear that they should at least consider more rehab and physiotherapy to see how their knee responds. Other people however will not be able to cope and their knee will feel painful and unstable and most likely surgery will be their best option.

In summary, the decision of whether to try physiotherapy or surgery after either an anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) injury is a complex one where the patient, physiotherapist and surgeon all need to consider a range of factors as to what will be the best option for the patient. Outside of the world of elite sport there are likely to be a series of factors such as age, current ability to cope with the knee, lifestyle, goals and ability to take a lengthy period off work that will influence which will be the most appropriate decision for any individual patient.

How Can ThreeSpires Physiotherapy Help with My Anterior Cruciate Ligament (ACL) or Posterior Cruciate Ligament (PCL) Injury?

Physiotherapy and an assessment by a physiotherapist can help in a number of ways if you have injured either your anterior cruciate  ligament (ACL) or posterior cruciate ligament (PCL) of the knee and one of our physiotherapists who is experienced with managing and treating cruciate ligament injuries will be able to help. We can help in a  number of ways:

  1. Assessment & Diagnosis of a Cruciate Ligament Injury: this as mentioned earlier is a vital part of managing your cruciate ligament injury and the sooner you have an assessment the sooner you will know what you are dealing with. Our physiotherapists will be able to comprehensively assess your knee, make a diagnosis and also identify underlying biomechanical causes of your cruciate ligament strain such as core weakness.
  2. Management Plan: once a diagnosis of either an injury to the anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) at the knee has been made it is vital that you get a clear and comprehensive plan to optimise your recovery whether this be surgery or physiotherapy. Your physiotherapist will be able to identify the best strategy for helping with your cruciate ligament injury and will be able to advise as to whether physiotherapy or surgery is best.
  3. Rehab post ACL or PCL surgery: our physiotherapists will be able to assist with physiotherapy and rehab after your ACL or PCL reconstruction and will be able to guide you through the exercises needed.

Okay, I hope that you have found this article about anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries helpful. Should you or anyone you know have a cruciate ligament injury or suspect that you have one please get in touch and one of our physios would be happy to help.




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