The anterior cruciate is a ligament which is present inside the knee linking the thigh bone to the shin bone. This ligament gives important feedback to the brain for activating the appropriate muscles, particularly when you are running, twisting and turning at speed.
Damage to this ligament leads to instability of the knee with recurrent giving way. The common injuries that cause damage to the anterior cruciate ligament (ACL) include sports injuries while playing football or rugby. A twisting injury to the knee while skiing is also a common way by which people injure their ACL. At the time of initial injury a popping sensation is felt in the knee followed by swelling of the knee which gradually settles down over a period of a few weeks but then leads to recurrent giving way, either during everyday activities or while engaging in sports.
Injury to the anterior cruciate ligament is diagnosed by a clinical examination followed possibly by an MRI scan of the knee. In the initial phases rest and physiotherapy is advised to reduce the swelling and regain the full movement in the knee. Not everyone needs knee surgery following injury to the anterior cruciate ligament. If your knee feels stable following a course of physiotherapy, you may not need knee surgery, provided you are happy to accept certain lifestyle changes. If your knee feels persistently unstable during everyday activities or you are keen to resume sporting activity which involves twisting and turning while running, you will need a reconstruction of the ACL. Many surgeons believe that reconstruction of a ruptured anterior cruciate ligament will protect the knee from further injury.
What happens during ACL reconstruction?
The knee surgery is usually carried out under a general anaesthetic with addition of a local nerve block for post-operative pain control.
Two of the hamstring tendons are used to reconstruct your anterior cruciate ligament. These tendons are removed via a small incision just below the knee. These tendons are doubled over to form a four strand graft which is used to replace your ACL. (It has been seen that the strength in your hamstrings returns almost back to normal within a year following the surgery.) The rest of the surgery is done by the arthroscopic (keyhole) surgical technique. Any associated injuries like a torn cartilage are dealt with at the time of the arthroscopy. Two tunnels are drilled, one in the lower end of the thigh bone and the other in the upper end of the shin bone. The tendons are pulled across the knee via these tunnels and fixed to the bone using screws which hold the graft firmly while it heals to the bone. Skin closure is carried out using metal clips.
What happens after ACL reconstruction?
Most patients stay overnight following ACL reconstruction. The next day the bandages around the knee are removed and you are mobilised by a physiotherapist. If you have been given a nerve block the front of the thigh may feel numb and the muscle at the front of the thigh (quadriceps) may not work, hence you may need to use a knee splint to support the knee while walking until the nerve block wears off. There are no specific restrictions following the knee surgery and you can put full weight through the leg and can start bending the knee straight away after the knee surgery. Following your discharge from the hospital you will need to attend physiotherapy on a regular basis. The physiotherapist will help you to regain the full movement in your knee as well as build up the strength in themuscles around the knee. The physiotherapist will help you to increase your activity progressively. By 3-4 months following the knee surgery youwill be able to run in a straight line. Six months following the knee surgery you
can start retraining for any sports that you want to engage in. You may need to wait for about nine months following the knee surgery before returning to active sports.
What can I expect from my knee following ACL reconstruction?
The knee surgery aims to restore the stability and 90% of patients are able to get back to their pre-injury activity level following the ACL reconstruction. However, you may not be able to return to your previous level of sport.
What are the risks of having an ACL reconstruction?
- Infection (1%): the wound site and the knee may become red, hot and painful. Infection is usually treated with arthroscopic washout of the knee and antibiotics.
- Deep vein thrombosis (DVT): this is a blood clot in the veins of the leg. The blood clot can go into the general circulation and go to the lungs, which is termed as pulmonary embolus. The best guard against DVT is to work with the physiotherapist and get all the joints and muscles going as soon as possible following the knee surgery.
- Rupture of the graft: the tendons used to replace your ACL may tear. This may occur following further trauma and may need to be managed with further knee surgery (revision ACL reconstruction).
- Less common complications include numbness of the skin on the front of the knee and stiffness of the knee.