ACL and Meniscal Injuries

Published: January 5th, 2022

What is an ACL and meniscus injury?


A ligament or meniscal injury involves the soft tissues of the knee sustaining damaged to varying degrees. These injuries can range from minor (the ACL being sprained/overstretched) moderate (partial tears) to severe (complete tears of the ligament and meniscal cartilage.)


You may suspect an ACL tear if you have a sudden, sharp pain in the knee accompanied by a popping noise, or if you are unable to weight bear – due to intense pain or instability. The knee may swell very rapidly, with a reduced range of motion and you likely will not be able to continue with your activity.


With a tear of the meniscus, swelling gradually increases 2-3 days post-injury. The knee may feel like it locks or something catches inside the joint, again with a reduced range of motion. 


It is important to find the extent of the injury that has been sustained to properly manage it; imaging is the most useful tool we have to assess this. An MRI of your knee may be required to fully assess the internal damage. Depending on the mechanism of injury, you may have already had this and an X-ray (to rule out fractures) in A&E, or been referred by your GP. Understanding what these scans show will help your medical team devise the best management plan for you; this can range from rest and physiotherapy to surgery.


Throughout these investigations, it is likely that bending and straightening (flexion/extension) the knee, as well as walking or weight bearing will hurt. We can take a look at the anatomy of the knee to help you understand why this is, and give an insight into what the scans might show.


The anatomy of Acl and meniscus


The knee is a hinge joint made up of different structures and layers; superficial tissues, muscle and tendons, fat, ligaments and cartilage, and finally bone. Let’s go through this in more detail to understand why you may be in pain, and visualise the different possible injuries.

The bones that make up our knee joint are the femur (thigh bone), tibia and fibula (lower leg bones) and the patella (kneecap). In traumatic injuries, it is possible to break any of these bones. If you are in extreme pain after an injury, you should go to A&E for an X-ray of these bones. A fracture of the leg bones often has an easier management than soft tissue injuries – usually a cast or splint for 6 weeks before physiotherapy. 

The quadriceps is the bulk of the muscle on the front of the thigh – the tendon from this muscle holds your patella in the right place, over the articular cartilage at the end of the femur . It’s possible to damage this tendon or dislocate the patella, which would result in instability and too much movement of the bone.

The knee joint is mainly stabilised by the ligaments that surround it – there are 4, which hold the bones together. Either side of the joint, on the medial (inside) and lateral (outside) of the knee, are the Collateral ligaments. These can be seen on the diagram below, labelled MCL and LCL. These ligaments prevent the knee from being bent sideways, and often tear or sprain during high impact sporting injuries. The other 2 ligaments are the Anterior cruciate and Posterior cruciate. These crossover deep in the centre of the joint, and both assist in stabilising the knee and ensuring smooth movement.



“Remember: Ligaments attach bone to bone, whilst tendons attach muscle to bone!”


The meniscus is a smooth layer of cartilage that sits in-between the femur and tibia. It lubricates the joint, allowing for smooth movement and acts as a shock absorber. The menisci also help distribute bodyweight – chronic obesity can damage the cartilage, leading to early onset osteoarthritis.


Causes of ACL and meniscus injury


The ACL is a robust ligament, with most injuries being mild to moderate. A sprain is the most common injury to be seen in clinics, and usually occurs in sports people, although this is not always the case.


Any activity that has you stopping/changing direction suddenly, twisting the knee (rotational force) or landing awkwardly can sprain the ACL. In more severe cases, it is possible to tear your ACL, although this is more likely to be from a direct impact to the knee (e.g. football tackle) or forceful dislocation. 

“The mechanism behind most ACL injuries comes from when a valgus force is applied to the knee, pushing it inwards.”

If you sustain a mild injury to the knee whilst performing routine daily activities, it would be reasonable to manage symptoms at home          yourself. First line management for any musculoskeletal injury would be PEACE and LOVE. If symptoms do not improve within a few days, consider booking an appointment a sports therapist, physiotherapist or referral from a GP for further investigation (NHS route). If you think you have a serious injury to the knee (traumatic/unable to weight-bear) then it is important to go to A&E as soon as you can.

This is so that fractures and anything more sinister can be ruled out, and it will put you on the right pathway for further investigations (like an MRI or X-ray.) Sometimes with severe injuries, surgery may be needed to repair damage. If this is required, your Doctor will  discuss the details of the operation and aftercare with you.


If you have a mild injury, the most important initial action to take is PEACE and LOVE. Doing this immediately can reduce swelling and pain, enabling you to start recovering earlier.

After seeing your healthcare practitioner and determining the extent of the injury, you should rest the knee and manage your pain effectively – painkillers like Ibuprofen are useful, as they also work to decrease inflammation. The minimum period of rest will depend on the severity of the injury, and could range from a few days, several weeks or in the worst cases up to 8 months +. It is important to rest your knee during this time, as over-working it can damage it further and cause more pain. The last thing we want to do is make the injury worse and lengthen the recovery time.

Once pain and swelling in the knee has decreased, you can slowly start to use it again; this will depend on the current levels of pain and how disabling the original injury was. If you were unable to walk after the injury, slowly starting to weight bear for a few minutes at a time is an easy way to regain this function. When exercising the knee like this, it is important not to push too hard – the phrase “no pain no gain” does not apply here!



Rehabilitation and reducing injury risk 


As always, prevention is always better than a cure. After recovering from your injury it is imperative to maintain strength and function, preventing a repeat injury. Being mindful of activities you engage in and how you use your knee is the key to this, as well as:

  • Identifying  how the original injury occurred, and working with your physiotherapist putting in preventative measures to reduce re-injury risk.
  • Develop surrounding muscle groups (quadriceps and hamstrings) to aid in strength and stability of the joint. 
  • Ensuring that you’re consistant and adhere to your programme to give you the best chance of recovery. 
  • Don’t exercise in conditions that put you at more risk; being over-tired, poor nutrition, feeling fatigued can increase your chances of injury. 
  • Improving overall health and fitness; quality sleep, a good diet and reduction in stress, smoking and alcohol all aid in recovery and prevention of injury. 


Takeaways for ACL and Meniscus injuries


  • Injuries to the ACL and meniscus can vary greatly in severity, and so proper investigation is essential.
  • Resting is the first step in recovery and cannot be hastened!
  • Home rehabilitation is the main step in regaining function, so sticking to your rehabilitation programme is essential. 
  • Don’t hurt yourself more trying to recover! Improvements are best made in small steps and adequate pain management.
  • Preventing a repeat injury is easier than recovering all over again; focus on strength and form/technique to reduce your risk.