Dr Richard Clarnette MBBS, FRACS (Orth)- Orthopaedic Surgeon Dr Richard Clarnette MBBS, FRACS (Orth)- Orthopaedic Surgeon
Dr Richard Clarnette MBBS, FRACS (Orth)- Orthopaedic Surgeon Dr Richard Clarnette MBBS, FRACS (Orth)- Orthopaedic Surgeon
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ACL Reconstruction


The anterior cruciate ligament is one of the major stabilizing ligaments in the knee. It is a strong rope like structure located in the centre of the knee running from the femur to the tibia.

When this ligament tears unfortunately it doesn't heal and often leads to the feeling of instability in the knee.

ACL reconstruction is a commonly performed surgical procedure and with recent advances in arthroscopic surgery can now be performed with minimal incisions and low complication rates.


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

Often other structures 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 & these may need to be addressed at the time of surgery.

History of Injury

  • Most injuries are sports related involving a twisting injury to the knee
  • It can occurs with a sudden change of direction, a direct blow e.g., a tackle, landing awkwardly
  • Often there is a popping sound when the ligament ruptures
  • Swelling usually occurs within hours
  • There is often the feeling of the knee popping out of joint
  • It is rare to be able to continue playing sport with the initial injury

Once the initial injury settles down the main symptom is 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.


The diagnoses can often be made on the history alone.

Examination reveals instability of the knee, if adequately relaxed or not too painful.

An MRI (Magnetic Resonance Imaging) 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.



  • Rest
  • Ice
  • Elevation
  • Bandage

Long term

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

Indications for surgery

Young patients wishing to maintain an active lifestyle.
Sports involving twisting activities e.g., Soccer, netball, football Giving way with activities of daily living.
People with dangerous occupations e.g., Policemen, firemen, roofers, scaffoulders.
It is advisable to have physiotherapy prior to surgery to regain motion and strengthen the muscles as much as possible.


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

The surgery is performed arthroscopically. The ruptured ligament is removed and then tunnels (holes) in the bone are drilled to accept the new graft. This graft which replaces your old ACL is taken either from the hamstring tendon or the patella tendon. There are advantages & 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 (usually 6 months).

The rest of the knee can be clearly visualized at the same time and any other damage is dealt with e.g., meniscal tears.

The wounds then closed often with a drain and a dressing applied.


  • Patients are admitted on the day of surgery and usually discharged the next day.
  • You have pain medication in hospital and will be discharged with tablets, it is very important that you take these regularly in the first few days.
  • A small drain placed in the knee at surgery is removed the following day.
  • A splint is used for comfort and to help your quadriceps (thigh) muscle to support the knee.
  • You will be seen by a physiotherapist who will teach you about the use of the brace and give you an exercise program.
  • The small incisions are covered with waterproof dressings, which should be left on for 3 weeks.
  • The splint and tubigrip (compression sleeve) can be removed for showering.
  • Put ice on the knee for 20 minutes at a time every 2 hours. (You will need to open the front of the brace for the ice to be effective. It is also helpful to take the tubigrip bandage off when you do this).
  • Post op review with Dr Clarnette will usually be at 2 to 3 weeks.
  • Physiotherapy needs to be arranged for one week after the operation.
  • If you have increasing redness around the wound or increasing pain and temperatures or feel unwell you should contact Dr Clarnette's office.


Physiotherapy is an integral part of the treatment and is recommended to 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 physiotherapy will be supervised by a physiotherapist and involve activities such as exercise bike riding, cross trainer, swimming (no kicking for first 3 months) for cardiovascular fitness. Specific exercises should include muscle strengthening, dynamic control, co-ordination and proprioceptive exercises. Cycling can begin at 1 month, jogging generally around 3 to 4 months. Jogging should commence once both Dr Clarnette and the physiotherapist are happy that the knee has minimal swelling, minimal pain and sufficient muscle control and strength. The graft is strong enough to allow sport at around 9 months. This is provided that a comprehensive rehab has occurred and that other factors such as confidence, fitness and sports specific training has been addressed. Professional sports persons can often return at 9 to 12 months.

The rehabilitation and overall success of the procedure can be affected by associated injuries to the knee such as damage to the 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 or sport specific demands and other social factors.

Acute Stage 1 (0-4 weeks)


  1. Wound healing
  2. Reduce swelling
  3. Full weight bearing
  4. Off crutches in 1-4 days
  5. Promote muscle control with quadriceps activation
  6. Protect graft using a hinged brace blocking 10 ° of terminal extension.
  7. Avoid hamstring strain.

Treatment Guidelines

  1. Pain and swelling reduction with ice, elevation, and a tubigrip bandage (compression sleeve). Ice should be used as often as possible and in the early stages for 20 minutes every 2 hours. This should be continued for the first week.

  2. Patella mobilisation.

  3. In the first four weeks the aim is to achieve a range of motion from 10° to 100° (this is the range that the brace will allow). The brace is to be used at all times. This includes overnight and should only be removed for the purpose of icing and to have a shower.

  4. Try not to use the crutches for more than 4 days. Full weight bearing at all times even when crutches are used. Walk with as normally as possible encouraging extension within the brace at heel strike.

  5. Avoid stretching hamstring in the first 10 days. Care should be taken when bending over to avoid overstretching

Stage 2 (4 - 6 weeks)


  1. Full active range of motion
  2. Normal gait with full weight bearing
  3. Minimal pain and swelling
  4. Improve muscle control
  5. Avoid hamstring strain
  6. Develop early proprioceptive awareness
  7. Stop using the hinged brace

Treatment Guidelines

  1. Use active, passive and hands on techniques to promote full range of motion.

  2. Progress closed chain exercises (quarter squats and small single leg lunges) as pain allows. The emphasis is on pain free loading with good dynamic control.

  3. Introduce gym based exercise equipment including low resistant leg press and stationary cycle.

  4. Water based exercises can begin if the wounds are healed. Hydrotherapy can assist gait retraining, early strength training and help with single leg control.

  5. Begin proprioceptive exercises including single standing leg balance on the ground.

  6. Bilateral progressing single calf raises.

  7. Avoid isolated loading of hamstrings. Hamstrings will be progressively loaded through closed chain and gym based activity. Begin early active hamstring contractions.

  8. Start gluteal strengthening - don't forget gluteus medius and lateral pelvic stability.

Stage 3 (6 - 12 weeks)


  1. Begin specific hamstring loading
  2. Increase total leg strength
  3. Promote good quadriceps control in lunging.

Treatment Guidelines

  1. Focal hamstring loading begins and is progressed steadily throughout the next stages of rehabilitation.
    • Active prone knee flexion 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 lift initially active increasing difficulty by adding dumbbells

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

  2. Gym based activity including leg presses or light squats and stationary bike, which can be progressively increased in intensity as pain and control allow. It is important to monitor any effusion (swelling) following exercise and if it is increasing then exercise should be toned down.

  3. Once single leg lunge control and single leg squat strength and endurance are comparable to the other side, hopping can be introduced.

  4. Avoid running, kicking, jumping, twisting and turning activities

Stage 4 - (3-6 months)

Prior to running certain criteria must be met:

  • Minimal anterior knee pain
  • A pain free lunge and hop that is comparable to the other side
  • Minimal knee effusion
  • Good control of pelvis and knee
  • An isokinetic strength test value of at least 70% (comparable to the non operated side) for quadriceps and hamstrings is recommended.


  1. Improve leg strength
  2. Develop straight line running
  3. Increase proprioception

Treatment Guidelines

  1. Controlled sport specific activities should be commenced including straight line running.

  2. Continue proprioception with hopping and balance correction

  3. Monitor potential problems associated with increasing loads including increased swelling (effusion) and anterior knee pain.

  4. Avoid open chain resistant leg exercises

Stage 5 (6-9 months)


  1. Improve running endurance and change of direction
  2. Introduce sports specific exercises

Treatment Guidelines

  1. Increase running endurance
  2. Jumping and landing techniques - encourage soft knee landing technique.
  3. Increase sharp turns during running around cones etc.

Stage 6 (9 - 12 months)


A safe return to sporting activities

Treatment Guidelines

  1. Full training for 1 month prior to active return to competition

  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 in training

  3. Progress difficulty and complexity of jumping and landing drills.

  4. Improve running endurance leading up to a normal training session

  5. Full range, no effusion, good quadriceps control for lunge, hopping and hop and turn type activity.

Stage 7 (After return to sport)


Maintain a healthy knee and avoid re-injury

Treatment Guidelines

  1. Ongoing proprioceptive training with appropriate level of difficulty.
  2. Ongoing maintenance strength program for key muscle groups such as quadriceps, hamstrings, gluteals, calf and abdominals.

Risks & 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.


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 & 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 minimized 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.

Dr Richard Clarnette - Orthopaedic Surgeon Meet Dr Richard Clarnette - Orthopaedic Surgeon
Meet Dr Richard Clarnette - Orthopaedic Surgeon
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© 2009 Dr. Richard Clarnette - Orthopaedic Hip & Knee Surgeon Adelaide Australia