ACL Injuries: Signs, Symptoms, Management, Surgical Protocol & Physiotherapy Rehabilitation

ACL  “Anterior Cruciate Ligament” Injury





52% of people injure their ACL in Australia per year…  that’s a cost of $75 million AUD on our health care system!

Want to see how easily an ACL (Anterior Cruciate Ligament) can rupture a career. Click play below…

As far as sporting injuries go, ACL’s would have to be one of the most talked about injuries out there. They are not only extremely painful but they can also have a huge impact on activity levels and returning to exercise/training and hence may be a daunting topic of thought for any high level athlete. There are also so many conflicting opinions about treatment options and recovery time and it can be hard to sift through all the available information.

In this blog, I will aim to gather all the latest research we have about ACL injuries to provide a brief outline of the injury itself and the treatment options available.

Firstly, let’s take a look at the knee anatomy…




In order for a particular joint to move in a controlled way, there are several different structures that need to work together:

  1. The Joint – The knee is classified as a hinge joint where the bottom of the thigh bone (femur) and the top of the shin bone (tibia) meet and move together to bend (flex) and straighten (extend) the leg.
  2. The Muscles – There are two main muscle groups that produce the straightening and bending action of the knee.

Quadriceps (at the front of the thigh) – straighten the knee.

Hamstrings (at the back of the thigh) – bend the knee.



Hamstrings muscle group (back of the knee)


Quadriceps muscle group (at the front of the knee)











The Ligaments – There are four main ligaments within and surrounding the knee.ACL

  1. Anterior cruciate ligament (ACL)– prevents the shin bone from sliding out in front of the thigh bone
  2. Posterior cruciate ligament (PCL) – prevents the shin bone from sliding backwards on the thigh bone
  3. Medial collateral ligament (MCL)– runs along the inside of the knee preventing the knee from bending in
  4. Lateral collateral ligament (LCL)– runs along the outside of the knee preventing the knee from bending out


The two muscle groups combined with these four ligaments work simultaneously to prevent excessive movement and stabilise the joint during movement to prevent injury.


Let’s have a deeper look at an ACL …

Paul Dardagan

Paul Dardagan (Bounce Physio Director) in theater inspecting the knee anatomy with an orthopedic surgeon (2016).

The anterior cruciate ligament (ACL) is band of dense connective tissue extending from the femur to the tibia that controls excessive knee motion by limiting joint mobility.

Together with the three other major ligaments in the knee, the ACL allows for a person to pivot and change directions quickly without the knee ‘giving way.’

During full knee flexion, all the ligaments in the knee, especially the ACL are in a ‘slack’ position however as the knee is straightened, the ligaments begin to stretch until the knee reaches full extension and the ligaments are under the most strain.

This is the position that people are most at risk of injuring their ACL as it is where the ligament is at its most vulnerable.






So if it takes that much force to cause injury, why are ACL injuries so common?

An ACL tear is most often a non-contact injury and can occur as the result of several different movements in these vulnerable positions, placing the ACL under extreme loads. For example:

  • When the femur and tibia rotate in opposite directions under full body weight (e.g. pivoting during snow skiing or dodging a defender in soccer)
  • Decelerating suddenly (e.g. often seen in netball)
  • Landing from a jump forcing your knee to bend outwards – valgus (e.g. semi contact jumping in basketball)






Poorly distributed body weight through the knee is an added complication which alters its optimal position. This causes an imbalance of forces through the knee and places extra pressure on the ACL. When this load increases to an amount that the ACL cannot withstand, it ‘gives way’ and is injured or torn.

They can however, also occur directly, for example by another player falling across the knee, pushing the leg into hyperextension (over straightening) causing the ligament to stretch.


Who is most at risk ?

Due to the reasons mentioned above, athletes who play sports requiring sudden changes in direction such as netball or soccer are more prone to these injuries.

Research has also found that females are at a greater risk of an ACL injury than males.images

A cohort study conducted by Hewett et al (2005) concluded that this was due to the fact that women tend to have an increased dynamic valgus and high abduction loads during activity which places the ACL under a lot more strain.

The image below depicts the correct (left) and incorrect (right) alignment of the knee showing an increased valgus load.


Correct = < ACL stress                     Incorrect = Valgus > ACL stress

The next image below, shows the increased valgus angle at the knee for females compared to males, placing the ACL under a greater stress:

download              images (1)F2.large

download (1)Signs and symptoms:

  • Locking
  • Giving way or collapsing – instability
  • Hearing  ‘pop’ or ‘crack’
  • Haemarthrosis (bleeding into the joint space) within 6 hours
  • Swelling

Additionally, it is never JUST an ACL injury – other ligaments are usually involved and it is common that there is bone bruising present. Sometimes the shock absorbing cartilage called the menisci is also damaged and may need to be surgically repaired.


There is both conservative and surgical management available for ACL injuries. Research shows that both options have similar long term outcomes however factors such as the severity of the injury, the timeframe in which the knee needs to recover, and the future demands of the person will influence the patient’s choice. It is important to look at the whole picture when deciding what treatment option is best for you. This includes age, sporting requirements, hobbies, activities of daily living, occupation, financial position and plans for the future.

For people such as athletes who want to return to sport as soon as possible, surgical management is usually recommended however for those with no time restrictions, conservative management may be the better option.

The physiotherapists at bounceREHAB will work with you to devise a management program that best suits your PRE-operative and POST-operative needs and goals. 


A nutritionist at bounceREHAB is also abioceuticals logovailable to take you through various BioCeutical supplement products
that will help your inflammation and enhance your collagen and pain recovery.

Long term promotion of good joint health is important to limit the pernicious consequences of an ACL tear such as early onset osteoarthritis and weight gain.

Conservative management:

Immediately following an ACL injury, the RICER first aid management technique can be (1)

  • R – Rest – sit down and stop playing the activity
  • I  – Ice – 20 minutes every two hours
  • C – Compression – wrap a medical or cold compressionbp-lm-805-p02_1bandage/garment tightly around the knee to prevent excessive swelling
  • E – Elevation – raise your leg above the level of the heart
  • R – Referral – go and see a doctor, a physiotherapist and orthopedic specialist

Upon seeing the doctor, crutches and/or range of motion brace may be needed, and analgesics are usually required. The doctor will also recommend that an MRI be conducted to see the extent of the ligament (and perhaps cartilage/bone) damage. If severe enough, patients may be referred to an orthopaedic surgeon to assess the severity of the injury and whether surgery is required. If surgery is not needed, the patient is usually referred to physiotherapy for conservative treatment.


Physiotherapy at bounceREHAB:

At bounceREHAB, the physiotherapists will assess the knee for the amount of instability present and conduct a series of special tests which will give them an understanding of the level of injury. After gathering a full understanding of your injury, they will discuss with you your personal treatment goals and work with you to devise an individualised management program. Such a program may be focusing on leg strengthening exercises, proprioception/balance and functional training which will get you back towards your pre-injury self in a steady and progressive way.

What is the aim of Physiotherapy?

  • Reducing inflammation and pain
  • Regaining normal range of motion
  • Increasing the strength of your lower limbs, in particular the quadriceps and hamstrings
  • Improving your biomechanics, particularly of your patella (knee cap) tracking
  • Improving agility, balance and proprioception
  • Improving your function and technique for activities such as walking, running, squatting, hopping and landing
  • Minimising your chance of re-injury

The time taken to return to light to moderate activities varies from person to person (usually 8-10 weeks) however a systematic review (Muaidi, Q.I., Nicholson, L.L., Refshauge, K.M. et al, 2007) suggests that with conservative management, normal knee function can be regained within 12 months.

All equipment needed for rehabilitation is available at bounceREHAB including; pilates reformer rehab classes, foam rollers, therabands, ice compression garments, microcurrent portable units, BioCeutical supplements, knee braces/supports. You physiotherapist will thoroughly educate you on how to best use them.

Take a look at some of our ACL patients Vijay and Kieran, smashing out their physiotherapy exercises!


single leg presses

Single leg presses to strengthen the quads to support the knee joint

Glute bridges on the reformer for an increased challenge!

Glute bridges on the reformer for an increased challenge!


Below is Kieran completing a series of reformer exercises including leg press and calf raises:



As recovery progresses, the exercise intensity and complexity is increased. Here is a video of Paul Dardagan our senior physiotherapist and director at bounceREHAB, challenging Kieran’s knee in terms of strength, power, agility and proprioception!



Surgical Management:

Most athletes who tear their ACL during sport will prefer to have the ligament surgically reconstructed as soon as possible (within 4 weeks of the injury) in order to return to training and competition. Sometimes, however, there is no urgency for the operation and it may in fact be better to let the knee settle down before surgery. In this case, prehab physiotherapy is recommended to prepare the knee for surgery.

The Surgery: 

ACL reconstructions are mainly performed arthroscopically, a minimally invasive procedure where an endoscope is inserted into the joint through a small incision. To take on the job of an ACL either part of the hamstrings or patella tendon is taken as a graft which forms the new ligament.  In most cases, part of the hamstring tendon is used however the patella tendon can also be used. These days, surgeons recommend using the hamstring tendon as there is good evidence of reduced risk of complications as well as reduced knee pain.

The surgeon will inspect the joint internally using a camera to confirm the damage to the ACL and view the internal state of the joint. The damaged ACL is removed and the joint ‘cleaned up.’ Two tunnels are drilled into the thigh and shin bones, which the graft is then pulled through and fixed into position. The surgeon will then assess the function of the new ligament before the arthroscopy incisions are closed up.


Here, Associate Professor Hope answers some frequently asked questions about an ACL reconstruction;

The process of an ACL reconstruction:




What about the Rehab?




Physiotherapy rehabilitation should start as soon as possible after surgery. bounceREHAB Physiotherapists work with your surgeon to guide a specific program tailored to each person.

For the first few weeks the main aim will be to reduce swelling, regain range of motion and achieve full weight bearing. Following this period, proprioceptive exercises and a muscle strengthening program will be given to the patient in order to get the leg back to a more functional state. Cycling and swimming may also be started at around the 4 week mark and light jogging can begin after around 3 months. It will not be until 6 months after the surgery that the graft will be strong enough to allow sport however other factors such as confidence and fitness levels may push this back until around 10-12 months post-surgery.



ACL injuries can have a huge impact on not only athletes and their sporting careers, but the daily activities of the people within the general population. Modifications to training, work and how one goes about their lives will need to be made and can often be drastic. There are however both conservative and surgical treatment options which, in the long term, have a great prognosis.

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Many thanks to A/Prof Nigel Hope for taking the time-out of his busy clinical schedule in Sydney to meet bounceREHAB’s Sydney University Physiotherapy students. The three physio students were very excited to have the opportunity to be sitting face to face with such an experienced orthopaedic surgeon. Thanks A/Prof Hope and his team for accommodating them and contributing positively to our patients knowledge base.



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