What is the anterior cruciate ligament?

ACL Reconstruction Melbourne – The Anterior Cruciate Ligament (ACL) is one of the major stabilising ligaments in the knee. It is a strong rope like structure located in the centre of the knee running from the femur (thigh bone) to the tibia (larger of the two bones between the knee and the ankle).

When the ACL ligament tears, it doesn’t heal and often leads to the feeling of instability in the knee.

Anterior Cruciate Ligament (ACL) reconstruction surgery is a commonly performed procedure and with recent advances in arthroscopic surgery can now be performed with minimal incisions and low complication rates.

Definition from MedicinePlus.

What is the function of the Anterior Cruciate Ligament?

The ACL is the major stabilising ligaments in the knee. It prevents the tibia (Shin bone) moving abnormally on the femur (thigh bone). When abnormal movement in this area occurs it is referred to as instability and you will be aware of this abnormal movement.

Often other structures in the knee such as the meniscus, the articular cartilage (lining the joint) or other ligaments can also be damaged at the same time as a cruciate injury and these may need to be addressed as well at the time of surgery.

History of ACL injuries

Most ACL injuries are sports related and involve:

  • A twisting injury to the knee
  • A sudden change of direction or direct blow/impact such as a tackle or landing awkwardly
  • A popping sound when the ligament ruptures or brakes
  • Swelling usually occurs very soon after
  • A feeling of the knee popping out of joint
  • Discontinuing playing sport with the initial injury
  • Main symptom of instability or giving away of the knee. This usually occurs with running activities but can occur on simple walking or other activities of daily living.

Diagnosing ACL injuries

Diagnosing an ACL injury can often be made on the history of the injury alone. An examination reveals instability of the knee, if adequately relaxed or not too painful.

A Magnetic Resonance Imaging (MRI) scan can be helpful if there is doubt as well as to look for damage to other structures within the knee.

At times the final diagnoses can only be made under anaesthetic or with an Arthroscopy.

Treatment of ACL injuries

Initial treatment of ACL injuries includes:

  • Rest – Cease movement and weight baring activity on the limb
  • Ice – Apply ice packs to the affected knee (See article on how to ice an injury properly)
  • Compression – Bandage
  • Elevation – Keep knee above the level of the heart

Long term treatment for ACL injuries

Not everyone needs surgery. Some people can compensate for the injured ligament with strengthening exercises or a brace. It is strongly advised to give up sports involving twisting activities, if you have an ACL injury.

Episodes of instability can cause further damage to important structures within the knee that may result in early arthritis.

Do you need ACL surgery?

You may wish to consider surgery if you:

  • Are a young patient wishing to maintain an active lifestyle
  • Participate in sports that involve twisting activities e.g., Soccer, netball and football etc
  • Have a serious determent to your daily living activities or job prospects.

It is advisable to have physiotherapy prior to surgery to regain motion and strengthen the muscles in your knee as much as possible.

ACL Reconstruction Melbourne

ACL Reconstruction Melbourne – Surgical techniques have improved significantly over the last decade, complications are reduced and recovery much quicker than in the past.

ACL surgery is performed arthroscopically meaning the surgery is performed with minimal trauma to the knee where possible. The ruptured ligament is removed and then tunnels (holes) in the bone are drilled to accept the new graft ACL. This graft replaces your old ACL and is either taken from the hamstring tendon or the patella tendon. There are advantages and disadvantages of each with the final decision based on surgeons preference.

The graft is prepared to take the form of a new tendon and passed through the drill holes in the bone. The new tendon is then fixed into the bone with various devices to hold it into place while the ligament heals into the bone. This usually takes approximately 6 months.

Any other damage to the can be seen during this process and dealt with as needed such as meniscal tears. The incisions are then closed often with a drain and a dressing applied.

Post ACL reconstruction surgery

Surgery is usually performed as a day only procedure or an overnight stay.

The following usually occurs after the operation:

  • You will have pain medication by tablet or in a drip (Intravenous).
  • Any drains will be removed from the knee.
  • A splint is sometimes used for comfort.
  • You will be seen by a physiotherapist who will teach you to use crutches and show you some simple exercises to do at home.
  • Leave any waterproof dressings on your knee until your post-op review.
  • You can put all your weight on your leg.
  • Avoid anti-inflammatories or aspirin for 10 days.
  • Put ice on the knee for 20 minutes at a time, as frequently as possible.
  • Post-op review will usually be at 7-10 days.
  • Physiotherapy can begin after a few days or can be arranged at your first post-operation visit.

If you have any redness around the wound or increasing pain in the knee or you have temperature or feel unwell, you should contact your surgeon as soon as possible.

ACL rehabilitation

Physiotherapy is an integral part after ACL surgery. I recommended you start as early as possible. Preoperative physiotherapy is helpful to better prepare the knee for surgery. The early aim is to regain range of motion, reduce swelling and achieve full weight bearing.

The remaining rehabilitation will be supervised by a physiotherapist and will involve activities such as:

  • Exercise bike riding
  • Swimming
  • Balance exercises and;
  • Muscle strengthening.

Cycling can begin at 2 months and jogging can generally begin at around 3 months. The graft is strong enough to allow sport at around 6 months however other factors come into play such as confidence, fitness and adequate fitness and training.

Professional sportsmen often return at 6 months but recreational athletes may take 10 -12 months depending on motivation and time put into rehabilitation. The rehabilitation and overall success of the procedure can be affected by associated injuries to the knee such as damage to meniscus, articular cartilage or other ligaments.

The following is a more detailed rehabilitation protocol useful for patients and physiotherapists. It is a guide only and must be adjusted on an individual basis taking into account pain, other pathology, work and other social factors.

ACL rehabilitation guidelines (0 – 2 Weeks)


  • Wound healing
  • Reduce swelling
  • Regain full extension
  • Full weight bearing
  • Wean off crutches
  • Promote muscle control

Treatment Guidelines

  1. Pain and swelling reduction with ice, intermittent pressure pump, soft tissue massage and exercise
  2. Patella mobilisation
  3. Active range of motion knee exercises, calf and hamstring stretching, contraction (non weight bearing progressing to standing), muscle control and full weight bearing. Aim for full extension by 2 weeks. Full flexion will take longer and generally will come with gradual stretching. Care needs to be taken with hamstring co contraction as this may result in hamstring strains if too vigorous. Light hamstring loading continues into the next stage with progression of general rehabilitation. Resisted hamstring loading should be avoided for approximately 6 weeks.
  4. Gait retraining encouraging extension at heel strike

Stage 2- Quadriceps Control (2-6 Weeks)


  • Full active range of motion
  • Normal gait with reasonable weight tolerance
  • Minimal pain and effusion
  • Develop muscular control for controlled pain free single leg lunge
  • Avoid hamstring strain
  • Develop early proprioceptive awareness

Treatment Guidelines

  1. Use active, passive and hands on techniques to promote full range of motion
  2. Progress closed chain exercises (quarter squats and single leg lunge) as pain allows. The emphasis is on pain free loading, VMO and gluteal activation
  3. Introduce gym based exercise equipment including leg press and stationary cycle
  4. Water based exercises can begin once the wound has healed, including treading water, gentle swimming avoiding breaststroke
  5. Begin proprioceptive exercises including single standing leg balance on the ground and mini tramp. This can progress by introducing body movement whilst standing on one leg
  6. Bilateral and single calf raises and stretching
  7. Avoid isolated loading of the hamstrings due to ease of tear. Hamstrings will be progressively loaded through closed chain and gym based activity

Stage 3- Hamstring/Quadriceps Strengthening (6-12 Weeks)


  • Begin specific hamstring loading
  • Increase total leg strength
  • Promote good quadriceps control in lunge and hopping activity in preparation for running

Treatment Guidelines

  • Focal hamstring loading begins and is progressed steadily throughout the next stages of rehabilitation
  • Active prone knee flexion which can be quickly progressed to include a light weight and gradually increasing weights
  • Bilateral bridging off a chair. This can be progressed by moving onto a single leg bridge and then single leg bridge with weight held across the abdomen
  • Single straight leg dead lift initially active with increasing difficulty by adding dumbbells

With respect to hamstring loading, they should never be pushed into pain and should be carefully progressed. Any subtle strain or tightness following exercises should be managed with a reduction in hamstring based exercises

  1. Gym based activity including leg presses, light squats and stationary bike which can be progressively increased in intensity as pain and control allow. It is important to monitor any effusions following exercise and if it is increasing then exercise should be toned down.
  2. Once single leg lunge control is comparable to the other side hopping can be introduced. Hops can be made more difficult by including variations such as forward/back, side to side off a step and in a quadrant
  3. Running may begin towards the latter part of this stage
  4. Prior to running certain criteria must be met – No anterior knee pain
  5. A pain free lunge and hop that is comparable to the other side
  6. The knee must have no effusion
  7. Before jogging start having brisk walks, ideally on a treadmill to monitor landing
  8. Action and any effusion – This should be done for several weeks before jogging properly
  9. Increased proprioceptive manoeuvres with standing leg balance and progressive hopping based activity
  10. Expand calf routine to include eccentric loading

Stage Four-Sport Specific (3-6 Months)


  • Improve leg strength
  • Develop running endurance speed, change of direction
  • Advanced proprioception
  • Prepare for return to sport and recreational lifestyle

Treatment Guidelines

  1. Controlled sport specific activities should be included in the progression of running and gym loads. Increasing effusion post running that isn’t easily managed with ice should result in a reduction in running loads
  2. Advanced proprioception to include controlled hopping and turning and balance correction
  3. Monitor potential problems associated with increasing loads
  4. No open chain resisted leg extension exercises unless authorised by your surgeon

Stage Five-Return to Sport (6 Months Plus)


  • A safe return to sporting activities

Treatment Guidelines

  1. Full training for 1 month prior to active return to competitive sport
  2. Preparation for body contact sports. Begin with low intensity one on one contests and progress by increasing intensity and complexity in preparation for drills that one might be expected to do at training
  3. To improve running endurance leading up to a normal training session
  4. Full range, no effusion, good quadriceps control for lunge, hopping and hop and turn type activity. Circumference measures of thigh and calf to within 1 cm of other side

ACL injury risks and complications

Complications are not common but can occur. Prior to making the decision of have this operation. It is important you understand these so you can make an informed decision on the advantages and disadvantages of surgery.

These can be Medical (Anaesthetic) complications and surgical complications.

Medical (Anaesthetic) complications

Medical complications include those of the anaesthetic and your general well being. Almost any medical condition can occur so this list is not complete. Complications include

Allergic reactions to medications – Blood loss requiring transfusion with its low risk of disease transmission Heart attacks, strokes, kidney failure, pneumonia, bladder infections. Complications from nerve blocks such as infection or nerve damage. Serious medical problems can lead to ongoing health concerns, prolonged hospitalization. The following is a list of surgical complications. These are all rare but can occur. Most are treatable and do not lead to long term problems.

Infection – Approximately 1 in 200. Treatment involves either oral or antibiotics through the drip, or rarely further surgery to wash the infection out.

Deep vein thrombosis – These are clots in the veins of the leg. If they occur you may need blood thinning medication in the form of injections or tablets. Very rarely they can travel to the lung (Pulmonary Embolus) which can cause breathing difficulties or even death.

Excessive swelling and bruising – This is due to bleeding in the soft tissues and will settle with time.

Joint stiffness – Can result from scar tissue within the joint, and is minimised by advances in surgical technique and rapid rehabilitation. Full range of movements cannot always be guaranteed.

Graft failure – The graft can fail the same as a normal cruciate ligament does. Failure rate is approximately 5%. If the graft stretches or ruptures it can still be revised if required by using tendons from the other leg.

Damage to nerves or vessels – These are small nerves under the skin which cannot be avoided and cutting then leads to areas of numbness in the leg. This normally reduces in size over time and does not cause any functional problems with the knee. Very rarely there can be damage to more important nerves or vessels causing weakness in the leg.

Hardware problems – All grafts need to be fixed to the bone using various devices (hardware) such as screws or staples. These can cause irritation of the wound and may require removal once the graft has grown into the bone.

Donor site problems – Donor site means where the graft is taken from. In general either the hamstrings or patella tendon are used. These can be pain or swelling in these areas which usually resolves over time.

Residual pain – Can occur especially if there is damage to other structures inside the knee.

Reflex Sympathetic Dystrophy – An extremely rare condition that is not entirely understood, which can cause unexplained and excessive pain.


Anterior Cruciate Ligament reconstruction is a common and very successful procedure. In the hands of experienced surgeons who perform a lot of these procedures 95% of people have a successful result. It is generally recommended in the patient wishing to return to an active lifestyle especially those wishing to play sports involving running and twisting.

The above information hopefully has educated you on the choices available to you, the procedure and the risks involved. If you have any further questions you should consult with your surgeon.

Discussing any surgical option can be stressful. So if you have any any questions please do not hesitate to email me.
I will get back to you as soon as possible – Dr. David Love.