Anterior Cruciate Ligament ACL Reconstruction

ACL Reconstruction Patellar Tendon

ACL Reconstruction Hamstring Method

About the ACL

The anterior cruciate ligament (ACL) is a 3-4cm long band of connective tissue that runs diagonally through the inside of the knee. It connects the femur (thigh bone) to the tibia (shin bone). It helps stabilise the knee joint when performing twisting and turning actions. The cruciate ligament is usually not required for normal daily living activities, however, it is essential in controlling the rotation forces developed during side stepping, pivoting and landing from a jump.

ACL is the most common injured ligament in the knee. It accounts for about 40% of all sporting injuries. The ACL is commonly injured whilst playing sports such as football, squash, tennis, other running ball sports or skiing. Whilst playing sports, momentum is developed and upon attempting a pivot, landing from a jump or side step manoeuvre, the knee gives way. When skiing, rupture may occur at low or high speeds. Commonly the binding fails to release as the ski twists the leg resulting in a tearing sensation.

Injury and Symptoms

Patients frequently hear or feel a snap, or crack accompanied by pain. Swelling commonly occurs within the hour, but is modified by ice or compression. Frequently pain is felt on the outer aspect of the knee as the joint dislocates. This dislocation may be felt to reduce with a clunk. The knee will feel unstable and patients will be unable to put weight on it straight away. Full range of motion is often lost and patients won’t be able to fully straighten their leg. About half of all ACL injuries, are associated with other knee ligament, menisci (shock absorbency discs) or cartilage (smooth protective layer covering the bone ends) injuries. ACL injuries can be partial, where part of the ligament is torn or stretched or complete, where the ligament is split in two or detached from its attachment to the bone.

Initial treatment of any knee ligament injury should consist of ice packs, compression bandages and crutches. It is difficult to weight bear for several days, however, after seven to ten days the swelling settles and walking is possible with the joint gradually returns to full movement. By four to six weeks following injury, the knee becomes almost normal. Patients who return to sport following injury usually notice a weakness or instability. Further episodes of instability may result in multiple injuries to the cartilages, menisci and the joint surfaces. Damage to these structures eventually leads to osteoarthritis in the long term.

The ACL unfortunately doesn’t heal on its own like majority of the ligaments and tissues in the body. This is because, unlike other ligaments about the joint, the ACL passes through the joint and is surrounded by joint fluid. Other ligaments heal by scar formation, however due to the unique location of the ACL the bleeding is uncontained, filling the joint, causing pain and swelling. Since there isn’t a localised contained blood clot, scar tissue does not form. The result is that the ACL rarely heals in continuity.


The goal of treatment of an injured knee is to return the patient to their desired level of activity without risk of further injury to the joint. Each patient’s functional requirements are different. Treatment may be without surgery (conservative treatment) or with surgery (surgical treatment). Those patients who have a ruptured ACL and are content with activities that require little in the way of side stepping, sharp twisting or turning (such as running in straight lines, cycling & swimming) may opt for conservative treatment. Sometimes if those patients who wish to pursue competitive ball sports, or who are involved in an occupation that demands a stable knee are at risk of repeated injury resulting in tears to the menisci, damage to the articular surface leading to degenerative arthritis and further disability in the long term. In these patients, surgical reconstruction is recommended.

Conservative Treatment

Conservative treatment is by physical therapy aimed at reducing swelling, restoring the range of motion of the knee joint and restoring full muscle power. Specific training to develop the necessary protective reflexes is required to protect the joint for normal daily living activities. As the cruciate ligament controls the joint during changes of direction, it is important to alter your sports to the ones involving straight line activity only. Social (non-competitive) sport may still be possible without instability as long as one does not change direction suddenly.

Surgical Treatment

This is usually determined by a variety of factors and following a detailed discussion with the patient at consultation. Patients who are unable or those unwilling to lower their level of activity, are at risk of causing further damage to their knee should they return to sporting activity and are advised to undergo surgical reconstruction. Other factors include, any other associated injuries, occupation, lifestyle and failure of conservative management.

Timing of surgery is very important and majority of the time, I wait for the swelling to completely settle, for patients to regain full range of motion in their injured knee and also for patients to build up their thigh muscles to as strong as possible with physical therapy. Hence, most commonly I prefer to try conservative ACL rehabilitation physical therapy for all my patients in the first instance and only then offer surgery following this period.

ACL Reconstruction Surgery

This involves placing a graft inside the knee by arthroscopic surgery (keyhole surgery procedure). A >90% success rate is expected with some deterioration over time depending upon other damage within the joint. Although ACL reconstruction surgery has a high probability of returning the knee joint to near normal stability and function, the end result for the patient depends largely upon a satisfactory rehabilitation and the presence of other damage within the joint. Advice will be given regarding the return to sporting activity, dependant on the amount of joint damage found at the time of reconstructive surgery. Sometimes, it is important to preserve damaged joint surfaces by restricting impact loading activity to delay the onset of degenerative osteoarthritis later in life.

The operation itself will involve a graft to be harvested to use to reconstruct the torn ligament. The graft I choose is patient specific and depends of various factors at the time of surgery. Usually I take 2 of the hamstring tendons, but sometimes other suitable graft choices such as the patella tendon and quadriceps tendon are also used. The details of these choices will be discussed prior to the operation.

The remnants of the torn ACL are removed with keyhole surgery and tunnels are made in the tibia (shin bone) and femur (thigh bone) to allow the graft to be positioned across the knee. The new reconstructed ligament is then fixed at both ends to secure it in place. My preferred choice of fixing the graft is using bio-absorbable screws but again sometimes depending on graft choices, other means may be used to fix the grafts.

Before the Operation

Pre-habilitation. Before surgery the knee must have a nearly normal comfortable range of movement. For the weeks leading up to the surgery patients should start some exercises that will help with your recovery.

Pre-habilitation exercises:
Before the operation it is important that patients have as near to full pain free movement as possible. Ideally a few weeks before the surgery patients should start exercises building up their quadriceps and hamstring strength. This trains the muscles up and makes it easier to get going after the surgery.
It is extremely important that there are no cuts, scratches or pimples on the lower limb as this greatly increases the risk of infection. The surgery will be postponed until the skin lesions have healed.

In Hospital

Majority of the patients are admitted on the morning of their surgery. You should inform your surgeon and anaesthetist, of any medical conditions or previous medical treatment as this may affect your operation. 

After the operation you will normally be required to stay in hospital for one night. Sometimes this can be done as a day case procedure and you may be able to go home on the evening of the operation (if this is the case, it will be discussed with you before your surgery).

After Surgery

You will wake up in recovery with the knee bandaged. You may have a small drain coming from the knee to help drain any excess bleeding and reduce the swelling. You will be given pain medications if required. It is safe to move the knee, but you will be encouraged when resting to keep the knee straight. It is safe to fully weight bear through the knee straight away, but often it is more comfortable to start walking with some elbow crutches. Most patients will only use these for the first few days.

Physiotherapy is commenced immediately post operatively and should continue for 4-6weeks. The physiotherapist will see you following the operation and go through the details of the rehabilitation program. They will keep a close eye on your recovery. For a couple of weeks after the operation, your knee will be swollen and stiff. You will be advised to elevate your leg. You may be given a cryo-cuff to take home with you as this helps with the swelling. Sometimes using a bag of frozen vegetables by wrapping it in a towel can be used on your knee to help the swelling.

By 7-10 days following surgery you should be able to walk without crutches. Sedentary and office workers may return to work approximately 5-7 days following surgery. Most patients should be walking normally 14 days following surgery although there is considerable patient to patient variation.

Should the left knee be involved then driving an automatic car is possible as soon as pain allows (usually 2 weeks). You must not drive a motor vehicle whilst taking severe pain killing medications. Should the right knee be involved driving is permitted when you are able to walk without crutches and have full control and mobility of your foot and ankle without any pain (usually 3 weeks). Please check with your insurance company that you are covered before starting to drive again.

Rehabilitation exercises should be continued intensively until 4 to 6 weeks when jogging under controlled conditions is commenced. These initial exercises will help you to regain full range of motion in your knee, strengthen your leg muscles and improve your balance.

Solo sport as part of a comprehensive rehabilitation programme commences at approximately 6-10 weeks. Ideal solo sports are cycling, swimming, shooting basket balls, or hitting a tennis ball against a wall.

Playing sport non-competitively or training is possible at 4 to 6 months. Training may commence when an adequate rehabilitation of the thigh musculature has occurred. A return to competitive sport is permitted only after 8 months following surgery, again provided that there has been a complete rehabilitation and the joint is demonstrated to be stable.


Common (2-5%)

Pain – You will have pain in the knee following the operation and you will be given some pain medication to take home with you.

Stiffness – Your knee will be stiff for a few days following the operation and you will not be able to fully straighten it or fully bend it straight away.

Swelling/Haemarthrosis – Your knee will be swollen for a few days following the operation, sometimes you get a collection of blood in the knee that the body will absorb over time and the swelling settles; rarely you may need this collection of blood draining.

Numbness –  A small percentage of patients experience some numbness and altered sensation on the front of the knee around the scars. This settles down to a certain extent with time but may not resolve entirely. It will not affect your function but kneeling may be an issue.

Less common (1-2%)

Infection – This is a serious but less common complication. The wounds can get infected or rarely the joint itself. Surgery is carried out under strict germ free conditions in an operating theatre. Antibiotics are administered intravenously at the time of your surgery. Any allergy to known antibiotics should be brought to the attention of your surgeon or anaesthetist. Despite these measures, following arthroscopic ACL reconstructive surgery there is about a 0.5% chance of developing an infection within the joint. The signs of infection are: wound sites becoming red, inflamed and painful and there may also be a discharge. This may require treatment with antibiotics or may require hospitalisation and arthroscopic washout of the joint. Subsequent to such procedures prolonged periods of antibiotics are required and the post-operative recovery is slowed.

Graft Failure – The graft may rupture or fail, particularly following more trauma after the operation and if there is an early return to sport without the full time scale of the rehabilitation program. Graft failure due to poorly understood biologic reasons occurs in approximately 1% of grafts and a further 1% of grafts rupture during the rehabilitation programme. After 2 years if you return to normal activities the risk of further ACL injury returns to near normal (about 1% each year for patients returning to high intensity sports), the risk of rupturing the reconstruction is similar to that of rupturing the ACL in the other knee.

Rare (<1%)

Blood Clots – Deep vein thrombosis and pulmonary embolus: Although this complication is rare following arthroscopic surgery, a combination of knee injury, prolonged transport and immobilisation of the limb, smoking all multiply to increase the risk. Any past history of thrombosis should be brought to the attention of the surgeon prior to your operation.

Compartment Syndrome – This is rare and happens when there is increased pressure in the leg and can damage nerves and vessels and if this happens you will need further emergency surgery to release the pressure in the areas involved in the leg.

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