If you tear the anterior cruciate ligament in your knee, you may need to have reconstructive surgery.
The anterior cruciate ligament (ACL) is a tough band of tissue joining the thigh bone to the shin bone at the knee joint.
It runs diagonally through the inside of the knee and gives the knee joint stability. It also helps control the back-and-forth movement of the lower leg.
Knee injuries can occur during sports such as skiing, tennis, squash, football and rugby. ACL injuries are the most common type of knee injury, accounting for around 40% of all sports injuries.
You can tear your ACL if your lower leg extends forwards too much. It can also be torn if your knee and lower leg are twisted.
Common causes of an ACL injury include:
- landing incorrectly from a jump
- stopping suddenly
- changing direction suddenly
- having a collision, such as during a football tackle
If the ACL is torn, your knee will become very unstable and lose its full range of movement. This can make it difficult to perform certain movements, such as turning on the spot. Some sports may be impossible to play.
Deciding to have surgery
The decision to have knee surgery will depend on the extent of damage to your ACL and whether it’s affecting your quality of life.
If your knee doesn’t feel unstable and you don’t have an active lifestyle, you may decide not to have ACL surgery.
However, when deciding whether to have surgery it’s important to be aware that a delay could cause further damage to your knee.
Examining your knee
After you’ve been anaesthetised, the surgeon will carefully examine the inside of your knee, usually with a medical instrument called an arthroscope (see below).
Your surgeon will check that your ACL is torn and look for damage to other parts of your knee. If there’s other damage, your surgeon might repair it during the surgery or it may be treated after your operation.
After confirming that your ACL is torn, your surgeon will remove the graft tissue ready for relocation.
A number of different tissues can be used to replace your ACL.
Tissue taken from your own body is known as an autograft. Tissue taken from a donor is known as an allograft. A donor is someone who has given permission for parts of their body to be used after they die by someone who needs them.
Before your operation, your surgeon will discuss the best option with you. Tissues that could be used to replace your ACL are listed below.
- A strip of your patellar tendon – this is the tendon running from the bottom of the kneecap (patella) to the top of the shin bone (tibia) at the front of your knee.
- Part of your hamstring tendons – these run from the back of your knee on the inner side all the way up to your thigh.
- Part of your quadriceps tendon – this is the tendon that attaches the patella to the quadriceps muscle, which is the large muscle on the front of your thigh.
- An allograft (donor tissue) – this could be the patellar tendon or Achilles tendon (the tendon that attaches the back of the heel to the calf muscle) from a donor.
- A synthetic graft – this is a tubular structure designed to replace a torn ligament.
The most commonly used autograft tissues are the patellar tendon and the hamstring tendons. Both have been found to be equally successful.
Allograft tissue may be the preferred option for people who are not going to be playing high-demand sports, such as basketball or football, as these tendons are slightly weaker.
Synthetic (man-made) tissues are currently used in certain situations, such as revision surgery and multi-ligament injuries.
The graft tissue will be removed and cut to the correct size. It will then be positioned in the knee and fixed to the femur (thigh bone) and tibia (shin bone). This is usually carried out using a technique known as a knee arthroscopy.
An arthroscopy is a type of keyhole surgery. It uses a medical instrument called an arthroscope, which is a thin, flexible tube with bundles of fibre optic cables inside that act as both a light source and camera.
Your surgeon will make a small incision on the front of your knee and insert the arthroscope. The arthroscope will illuminate your knee joint and relay images of your knee to a television monitor. This will allow the surgeon to see the inside of your knee clearly.
Additional small incisions will be made in your knee so that other medical instruments can be inserted. The surgeon will use these instruments to remove the torn ligament and reconstruct your ACL.
Your surgeon will make a tunnel in your bone to pass the new tissue through. The graft tissue will be positioned in the same place as the old ACL, and held in place with screws or staples that will remain in your knee permanently.
After the graft tissue has been secured, your surgeon will test that there is enough tension in it (that it’s strong enough to hold your knee together).
They’ll also check that your knee has the full range of motion and that the graft keeps your knee stable when it’s bent or moved.
When the surgeon is satisfied that everything is working properly, they’ll use stitches to close the incisions and apply dressings.
After the procedure, you’ll be moved to a hospital ward to begin your recovery.