Knee Procedures
ACL Reconstruction

ACL is the abbreviation for the Anterior Cruciate Ligament. This is one of the major stabilising ligaments within the knee. It connects the femur (thigh bone) to the tibia (leg bone) and prevents abnormal movement (instability) occurring between the two. More specifically it provides rotatory stability to the knee to allow movements such as pivoting or sudden change in direction to occur without the knee giving way.

How does the ACL get injured?

The most common mechanism of injury is from a non-contact injury that typically occurs whilst attempting a pivoting or cutting (change of direction) manoeuvre during sport [Figure 1]. The injury can also occur from contact activity (e.g. being tackled from the side) when your knee buckles inwards whilst the leg is held in a fixed position. Not uncommonly, a “cracking or popping” sensation is felt at the time of the injury. The injury is associated with a lot of swelling within the knee that typically occurs at the time of, or soon after the injury. The leg is often painful to walk on for several days.

Figure 1. Picture of torn ACL

Figure 1. Picture of torn ACL

Other associated injuries

An ACL rupture may be associated with an injury to other stabilising ligaments within the knee. Rupture of your ACL is commonly associated with tears that involve the shock absorbing cartilages (menisci) of the knee. Depending on the location and size of these tears, they may be surgically repaired or trimmed at the time of your surgery. Bruising (oedema) of the bones also occurs at the time of injury because your femur and tibia are driven into each other by the violent forces that cause the ligament to rupture. No specific treatment is required for this “bone bruising”.

Initial Management

The first line of treatment following injury to the ACL should be those of the RICE principle (Rest, Ice, Compression, and Elevation). Early review by a physiotherapist is important to reduce swelling, improving movement and minimise wasting of muscles around the knee joint. Crutches are generally recommended to avoid excessive weight on the injured limb primarily during the early stages until you can walk without pain.

Goals Of Treatment

The treatment of ACL tears will vary across individuals based on their expectations, lifestyle, sporting aims etc. The major aim is to return the patient to their desired level of activity, both in regards to sport as well as other activities such as your occupation, whilst minimising the risk of injury to other structures within the knee.

Conservative Treatment

Patients with an ACL tear who do not wish to return to pivoting sports can often be managed with this approach. Running in a straight line, swimming, bike riding and golf are activities that are suitable. Physiotherapy is critical in the recovery phase to restore movement and strength to the lower limb. The latter phase of your rehabilitation should focus on proprioceptive re-training. These are exercises that improve the protective reflexes around the joint to minimise further instability episodes and reduce the risk of further joint injury.

When is an ACL Reconstruction recommended?

Most patients who want to return to pivoting sports will require a reconstruction to prevent their knee buckling during these activities. Other indications for surgery include young patients with high activity levels and people who work in an environment where knee stability is critical for safety and function. If your knee is giving way regularly and this is interfering with your quality of life, you may want to consider an operation. This instability may occur during sport or during activities of daily living.

When should the surgery occur?

An ACL reconstruction is not an urgent or emergency operation. The best outcomes from reconstructive surgery have been shown to occur in people whose knees have had some time to stabilise and recover. In the majority of cases, we prefer to rehabilitate your knee prior to undergoing surgery. Long term studies suggest that there is a lower risk of injury to the meniscus if surgery is performed within the first 6 months, when compared to those who do not have surgery. For elite athletes, surgery will usually be performed after a shorter period of rehabilitation. Occasionally, ACL reconstruction surgery is required sooner such as when other ligaments on the outer side of the knee (posterolateral corner) are torn or when a displaced tear of the meniscus is causing the knee to lock.

Pre-operative Rehabilitation

Physiotherapy prior to surgery is important to reduce the swelling, regain movement and limit the loss of strength in the muscles around your knee. It also teaches you the exercises needed for rehabilitation after the surgery.

What Graft Choices Are Available?

The ACL is reconstructed using a graft to replace the torn ligament. The idea is for the graft to biologically incorporate within the knee and restore stability to the injured limb. At SKS, we recommend use of the hamstring (HS) tendons for the majority of patients [Figure 2]. The hamstrings lie at the back of the thigh and connect to the inner side of the tibia below the knee. One or two tendons are removed to form a graft of adequate thickness. The HS ACL Reconstruction has the advantages of a faster post-operative recovery, better cosmesis and less post-operative pain with kneeling and squatting activities. SKS use special techniques (quadruple semitendinosus, 6-strand and 8-strand grafts) to optimise the diameter of the new ACL to maximise its strength.

Figure 2. Side view of knee, showing attachment of hamstring tendons to medial (inner) tibia bone. The 25cm length gracilis and semitendinosus tendon are removed through a 3cm incision over the pes anserinus, using a special device called a tendon stripper.

Other graft options exist including patellar tendon bone grafts (PTB) [Figure 3], the quadriceps tendon (from the front of the thigh to the kneecap) and cadaveric grafts (allografts). We do not advocate the use of any synthetic grafts (eg LARS) because of concerns of greater risk of long term damage to the knee joint surfaces. There are pros and cons to all graft choices and a discussion with the operating surgeon will determine what is best for you.

Figure 3. Patellar Tendon Bone Graft. The middle one-third of patellar tendon is removed with 25mm bone attachments on either end.


Things to do before your operation

Prior to undergoing surgery you will have further imaging of your knee to assess for associated injuries. The best test for this is an MRI scan [Figure 4] which allows accurate assessment of damage to all the soft tissues around the knee such as other ligaments, cartilage and menisci. This will aid with the planning of your surgery and also allow us to provide you with more accurate information with regards to your likely rehabilitation program. Do not shave or wax the leg prior to surgery, and cease smoking and any blood thinning medications.

Your rehabilitation after the operation is an important factor in the success of your surgery. Please ensure that physiotherapy is organised prior to your surgery so you can get to know the therapist who you will be working with and that you will have an understanding of the exercises required following surgery. Please ensure your physiotherapist has a copy of the SKS ACL Accelerated Rehabilitation Protocol. This can be downloaded at, or faxed to your physio from our office.

Figure 4. MRI scan showing tear of ACL

What happens on the day of your operation?

You will be admitted to hospital on the day of your surgery. Your anaesthetist will discuss with you the type of anaesthetic you will have and your options for post-operative pain relief. Most patients have a general anaesthetic. Antibiotics are delivered via a drip to decrease the risk of developing an infection. After your anaesthetic has been administered, a tight band (tourniquet) will be applied to your upper thigh and everything except your knee will be covered by sterile drapes.

One or two of your hamstring tendons (gracilis and semitendinosis) will be removed from the back of your thigh through an incision on the front of your knee. This is done with a special instrument called a tendon stripper. In some cases (eg. a revision operation), the knee cap ligament (the middle third of the patellar ligament) or the hamstring tendons from your opposite leg may need to be used.

With the aid of a specialised telescope (arthroscope), the inside of your knee is inspected for any associated damage. If any is found (eg. a meniscal tear), it will be addressed at the time of surgery. A tunnel will be drilled through the tibia and femur at the anatomic positions of the ACL. The tendons will be passed through these tunnels and anchored in place with specialised implants (screws and buttons) to provide fixation to your new ligament. [Figure 5]

Figure 5. ACL reconstruction using HS tendons and button fixation (Arthrex)

Your knee will be injected with local anaesthetic to help reduce post-operative pain. All your wounds will be closed using a combination of normal and dissolving sutures. Your leg will then be wrapped in a well-padded dressing prior to leaving the operating theatre. A brace is not usually required after your surgery.

You will wake up in the recovery ward where you will be closely monitored until you are ready to return to your ward. Here you will continue to be observed until you are fully awake. An x-ray of your knee will be taken the day of your surgery. During your stay, you will be seen by a physiotherapist who will provide you with exercises for your knee and assist you in walking. You will be able take all your weight through the operated leg after the operation. Once you are mobilising safely and your pain is controlled by oral pain medication, you will be able to go home. The majority of patients can be discharged home on the same day as their surgery.

What happens after you go home?

During the first week at home, your knee will be swollen and feel stiff. It is normal to require regular pain medication during this period. It is of utmost importance that you perform your rehabilitation exercises regularly whilst at home so that you get the greatest possible benefit from your surgery. These exercises are given to you on an instruction sheet prior to your hospital discharge. Prior to discharge from hospital, a post-operative visit to your surgeon will be organised approximately 10-14 days following your surgery.

Post-operative Rehabilitation

Physiotherapy (rehabilitation) is critical to the success of the surgery. If you cannot strictly follow the necessary precautions and rehabilitation, then it is best off not having surgery as complications such as graft loosing, graft rupture, stiffness and chronic pain can result.

It is important to start physiotherapy within 2-4 days of your surgery. You will require physiotherapy twice a week for approximately 6 weeks then reducing the amount of visits after this. Rehabilitation after an ACL reconstruction takes approximately 6-12 months. During this period you will take part in a structured rehabilitation program with your physiotherapist, and gradually return to your normal activities. This process is designed to safely improve the strength, motion and balance (proprioception) in your knee whilst the ACL graft heals. [See ACL Rehabilitation Protocol]

As a general rule, you are walking with crutches for approximately one week, commence stationary bike exercise by 2 weeks, jogging in straight line by 3 months and commence sports specific agility drills (PEP program) and non-contact training by 6 months. Return to sports is any where between 9-12 months and is determined by many factors including the speed of recovery, associated injuries to the joint and the age of the patient. Patients 18 years or younger are often held off sport for 12 months as studies now show that this age group has a much higher chance of injuring the graft again. You will have follow-up visits with your surgeon at 2 and 8 weeks, then six and twelve months after your surgery.

Frequently Asked Questions

When can I return to my normal sporting activities?

Most people return to sport somewhere between 9 to 12 months. This will depend on the appropriate completion of the rehabilitation program, as well as the PEP program.

When can I return to work?

If you work in an office setting, you may be able to return to work within 7-10 day. However, if your occupation requires a lot of walking or heavy manual labour, your return to work may be more prolonged, and may require a period of time on restricted duties.

When do I commence physiotherapy?

Physiotherapy usually starts 2-3 days after surgery. You will also see a physiotherapist in hospital who will teach you how to walk with crutches and demonstrate some exercises to do when you go home.

When can I drive again after surgery?

As a general rule, you cannot drive until you are off crutches and are not taking pain-killers that can cause drowsiness such as endone.

Will I have pain after the operation?

Most people will have mild to moderate pain in and around the knee for 2 weeks after surgery. This is generally well controlled with regular oral medication, ice and rest.

What complications can occur from surgery?

It is important to realise that complications can occur and are usually unpredictable. All due care is taken before, during and after the operation to try to ensure that complications do not occur. Sometimes complications may occur despite ever effort being made to avoid them. Should a complication occur, you will be informed and advised on the most appropriate treatment required to optimise the outcome of the initial surgery. If you have any questions or concerns during your recovery, it is important to contact your surgeon at SKS on (02) 8307 0333, or ring the hospital where the surgery occurred out of hours and they can be notified.

The most common complications following ACL Reconstruction surgery are:

  • Infection – infection following this procedure is uncommon (<1 in 250). This can either be a superficial (minor) infection involving the incisions, or a deep infection involving the knee joint and bone. If a deep infection occurs, admission to hospital is required as are intravenous antibiotics. A knee arthroscopy is performed to wash the infection out. Antibiotics are given prior to the operation to reduce the risk of infection. There is a higher infection risk in smokers and as such it is highly recommended you cease smoking approximately two weeks prior to your surgery. It is also important to prevent any cuts, rashes or abrasions developing around the knee joint prior to surgery as they increase the risk of infection, and your surgery will have to be delayed until they have resolved.
  • Blood clots “Deep Venous Thrombosis” – the risk of developing a blood clot in a calf muscle vein is approximately 1 in 50. Very rarely these blood clots can break away and travel to your lungs. This is called a “pulmonary embolus”. The risk of developing a pulmonary embolus is exceedingly rare. If you develop calf pain or tenderness following your surgery, you should contact your surgeon or family doctor immediately. An ultrasound examination will be performed of the calf to assess for a blood clot. To minimise the risk of a blood clot, it is important to notify your surgeon if you have any hereditary risk factors for blood clot formation, or if you have experienced a blood clot in the past. You should also cease smoking as this increases the risk of this complication. The combination of the oral contraceptive pill or HRT with smoking increases the risk of DVT as well. These factors should be discussed with your surgeon prior to your operation.
  • Bleeding – Occasionally, minor bleeding can occur which normally settles with compression and rest. Major bleeding is exceedingly rare.
    Nerve or Vascular Injury – There is a very rare complication but can result in either numbness, or loss of power of the muscles that move the foot and ankle (foot-drop) or damage to the circulation of the lower leg.
    Re-rupture or tear of the graft – This can occur any time following surgery, but the highest risk in the first 2 years, when the graft is maturing and neuromuscular control is still sub-optimal. The greatest risk factor for this is age under 18. It is critical you comply with your rehabilitation protocol to ensure you do not damage the graft during the healing phase.
    Numbness around the cuts – It is common to have numbness around the surgical incisions, but especially on the outer lower side of the leg. This numb patch usually resolves over several months. Occasionally a permanent patch of numbness can be experienced but is not problematic.
    Hamstring-related problems – The hamstrings regenerate in most people to a point where no subjective difference in power is noted. During the first 6 weeks after surgery, you may experience tear or a pop as though it has been injured. This is common and occurs from injury to early scar tissue that is forming.
  • Stiffness – There is a risk of developing knee stiffness following the surgery. If this occurs, you may require a second operation where the knee is either manipulated or scar tissue is removed arthroscopically from the inside of the knee joint. In order to prevent stiffness following the operation, it is important to have good range of motion prior to surgery and perform regular stretching exercises. Most importantly, you must participate in the post-operative rehabilitation program under the care of your physiotherapist.
  • Hardware related-complications – As metal buttons and screws are required to hold the graft in position, these may become prominent and cause irritability of either the skin or tendons. Sometimes, screws or buttons may need to be removed.
  • Ongoing swelling, pain or instability – Despite the surgery being performed appropriately, there is a chance that you have ongoing pain or swelling in your knee from injury to other structures in you joint. This may require further surgery on the knee in the future.

If you have any concerns or questions about this operation, please contact your surgeon at Sydney Knee Specialists on (02) 8307 0333.

ULTRABUTTON* Device and BIOSURE* REGENESORB Screw for ACL Reconstruction with a Hamstring Graft

ACL Reconstruction Patellar Tendon

ACL Reconstruction Hamstring Method