Anterior cruciate ligament (ACL) tear

• A torn anterior cruciate ligament of the knee (ACL) is one of the most common sports injuries, with a higher incidence in contact sports.
• The best option for repairing an ACL tear is knee arthroscopy surgery.
• Recovery time after ACL reconstruction varies between 3 to 6 months.

The anterior cruciate ligament of the knee is the most frequently injured of the 4 major ligaments of the knee. 

It is an elastic band made of collagen fibres whose function, like that of the posterior cruciate ligament, is to provide stability to the knee by joining the femur and tibia, while the function of the anterior cruciate ligament in movement is to prevent the femur from moving excessively forward over the tibia, taking advantage of its position in the knee at the front.

Although the anterior cruciate ligament is relatively small, it is a vital part of the proper functioning of the knee. This is why when it ruptures, the stability of the knee is compromised and it is very likely that a knee ligament reconstruction surgery will be required.

Anterior cruciate ligament (ACL) tear is one of the most frequent injuries in sports, and its incidence is particularly striking in sports such as football, skiing and basketball, as it is common to turn the knee in these sports. 

It is estimated that around 16,000 anterior cruciate ligament reconstruction operations are performed in Spain, with knee arthroscopy being the most commonly used.

It is important to note that women who play sports are more likely to suffer an ACL tear than men. This may be due to several factors such as the musculature of the joint, the dimensions of the pelvis, hormones during menstruation etc.

Anterior cruciate ligament (ACL) tears often occur at the same time as other knee injuries. It is very common for an ACL tear to occur together with a medial cruciate ligament tear and damage to the lateral meniscus.

The mechanism of anterior cruciate ligament rupture is mainly due to the following causes:

• Abrupt change of direction in which the upper trunk rotates but the leg remains pinned to the ground. A clear example occurs in sports such as football where changes of direction with acceleration or braking are very common.
• Poor support after a jump. Another of the most common ways to rupture the anterior cruciate ligament of the knee is when falling after a jump. If you step wrongly, it is very likely that together with the force involved in the fall, the ligament will not withstand the effort and will rupture.
• Lateral trauma. During contact sports, it is possible to be hit, tackled or tackled by another player. If the foot of the player who has been hit remains stuck to the ground, it is possible that the anterior cruciate ligament may be torn.
• Traffic accidents. Ruptures of the ACL are also common in accidents, especially motorbike crashes.

Types of anterior cruciate ligament (ACL) tears

When the anterior cruciate ligament ruptures, depending on the amount of ligament damaged, the rupture can be divided into a partial or complete rupture:

• Partial rupture of the anterior cruciate ligament. In these cases, only part of the ligament has been damaged by excessive twisting of the joint, so conservative treatment is possible, aiming to regenerate the ligament and improve and strengthen the adjacent structures, i.e. strengthen the muscles (hamstrings, quadriceps, adductors, calf muscles, etc.).
• Complete rupture of the anterior cruciate ligament. In the event that the anterior cruciate ligament rupture is complete and the patient is not an elderly person who is not going to make great physical efforts, the best and only option is surgical treatment, with the knee arthroscopy surgery for the reconstruction of cruciate ligaments being the most recommended. This technique has numerous advantages over open surgery, the most important of which is the reduction in postoperative recovery time.

Treatments for ruptured anterior cruciate ligament of the knee

As we mentioned in the previous section, the treatment to follow after a ruptured anterior cruciate ligament of the knee depends on a number of variables, the main one being the severity of the rupture, since if it is complete, knee ligaments surgery is recommended in most cases. 

Similarly, it is important to take into account the patient's own characteristics, both physical and lifestyle, since if the patient is an elderly person who is not active in sports, it is possible to avoid surgery. 

Below we differentiate the lines to follow depending on which treatment is chosen for anterior cruciate ligament tear:

• Conservative treatment for anterior cruciate ligament tear. To recover from a ruptured anterior cruciate ligament, in the case of a partial rupture, the first thing to do is to stop playing sports. The orthopaedic surgeon you have seen will indicate the exercises and rehabilitation techniques you should follow to recover from the injury, although some of the key principles in rehabilitation are the rapid start of isometric muscle strengthening exercises, mainly the quadriceps, the use of protective knee pads or bandages.
• Surgical treatment for anterior cruciate ligament tear. In the event that the anterior cruciate ligament rupture is complete and the trauma specialist recommends it, the best option is to carry out a cruciate ligament reconstruction operation. This consists of replacing the damaged ligament, in this case the anterior cruciate ligament, with a graft taken from the patient himself or from a donor bank.

It is important to mention that in many cases patients who have suffered a ruptured anterior cruciate ligament and have not undergone reconstructive surgery may have early degeneration (after about 15 years) in the other soft structures of the knee such as the meniscus and cartilage.

Ruptures of the anterior cruciate ligament, as well as the rest of the knee ligaments, are likely to be repaired by surgery. For this purpose, there are several types of surgical interventions, although the most common are knee arthroscopy (the most common nowadays) and open surgery. 

The following is a step-by-step explanation of the process involved in anterior cruciate ligament reconstruction:

Knee arthroscopy for anterior cruciate ligament (ACL) tear

After a prior consultation with the traumatology specialist, deciding that the best or only option is surgical intervention and performing the necessary pre-operative procedures to be able to carry out the operation as safely as possible, both in terms of surgery and anaesthesia, the patient is admitted to hospital for the operation.

In the hospital room, the nursing team will give you instructions to follow prior to the knee arthroscopy operation for the reconstruction of the anterior cruciate ligament. 

These include:

• Fasting for 8 hours prior to surgery so that the stomach is empty when the anaesthesia is administered.
• Administration of prophylactic antibiotic treatment to prevent infection. This can be done either the day before the knee arthroscopy or 10 minutes before the operation.
• Injection of anticoagulant medication to prevent blood clots.

On the day of the surgery, the patient will be taken to the operating theatre where he/she will meet the anaesthesiologist, the surgeon who will perform the ACL reconstruction and one or two members of the nursing team.

The anaesthesia used for cruciate ligament repair is usually regional anaesthesia (the lower part of the body is put to sleep) with sedation (the patient is put into a deep sleep so that they can be kept asleep without the need for intubation).

Once the anaesthesia has taken effect, the knee arthroscopy operation (cruciate ligament reconstruction) begins:

1. If necessary, the surgeon will shave the hair from the knee and clean the area with an antiseptic solution. The surgeon will then make three mini-incisions around the knee through which the surgery will be performed.
2. Through one of the mini-incisions made, the surgeon will introduce a saline solution into the joint capsule to expand it and remove any cloudy fluid that may hinder the surgeon's vision through the arthroscope.
3. The next step is the introduction of the arthroscope, which is a fibre with a video camera and a light at its distal end connected by fibre optics to a monitor, to determine the extent of the tear or rupture of the anterior cruciate ligament or if there is also any other damage to the rest of the knee (bone fracture, meniscus, other ligaments) to specifically adapt the surgery to each case.
4. Next, using the surgical tools introduced through the remaining incisions in the knee, the surgeon will carefully remove the damaged anterior cruciate ligament.
5. The next step is to prepare the bones to receive the new anterior cruciate ligament to be grafted. To do this, the surgeon will make a pair of tunnels in the bone, exactly where the old ligament was, to place the new ligament.
6. For the fixation of the new anterior cruciate ligament, it will be fixed to the bone with screws and other surgical elements typical of this type of intervention. Over time, the bone will grow around the screw and ligament, filling the gap, which will further improve the fixation and stability of the new ligament.
7. After the entire process, the surgeon will check that no damage has been done to the other elements of the knee, remove the surgical instruments used to reconstruct the ligament, and finally empty the joint of the saline fluid introduced at the start of the operation.
8. Before finishing, the surgeon sutures the incisions and gently dresses the knee.

Once the knee arthroscopy surgery (cruciate ligament reconstruction) is finished, the anaesthesiologist will start waking the patient up. The patient will remain in the operating room until he/she is fully awake and able to speak and move normally. 

After awakening, the patient will be taken to the resuscitation room where he/she will remain until his/her vital signs are completely normalised.

The duration of the knee arthroscopy surgery to repair an anterior cruciate ligament (ACL) tear is between 30 and 90 minutes, depending on the patient's characteristics and whether more knee structures are repaired.

Open surgery to repair an anterior cruciate ligament tear

The operation of cruciate ligament reconstruction with open surgery is the same as knee arthroscopy, with the main difference being that in this case the surgery is carried out through an open incision, which will considerably increase the length of hospital stay and postoperative recovery time. 

The final results are equally good in both methods, although nowadays the most commonly used intervention is knee arthroscopy, with statistics indicating that 1 in 5 arthroscopies performed in Spain are for reconstruction of the anterior cruciate ligament.

Recovery after an anterior cruciate ligament rupture depends directly on the surgical technique used to perform the reconstruction surgery. 

This is mainly due to the fact that if knee arthroscopy has been performed, the surgical incision is much smaller than in open surgery, which leads to less pain and the possibility to start rehabilitation much earlier.

In this case, recovery varies from 3 to 6 months, depending on the intensity of the rehabilitation carried out by the patient, although in the vast majority of cases the knee is back to 100% after 6 months.

Similarly, as far as the hospital stay is concerned, with knee arthroscopy surgery, it is reduced to just 2 days (in some cases the patient can even go home the same day), while in cases of open surgery it can be as long as 4 or 5 days.

After leaving the hospital, the patient will probably have to use a crutch for the first few weeks to avoid bearing full weight on the operated knee. This does not mean that the patient should leave the knee immobilised, as it is recommended and vital that rehabilitation begins as soon as possible to prevent the muscles of the joint from atrophying and to help blood flow to the area to aid healing and recovery of the knee.

In the past, when an athlete suffered an anterior cruciate ligament rupture, it meant the end of his or her career. Today, thanks to new surgical techniques and medical advances, it is possible for an elite athlete to recover from an ACL tear and be back to 100%.

The most important thing when returning to sport is to be aware of the risk of knee injuries. 

In order to prevent knee injuries, it is best to strengthen the muscles that are part of the knee's stability. In this way, the pressure and force exerted on the joint during movements is distributed and does not fall entirely on the ligaments of the joint, considerably reducing the chances of a relapse.

The latter recommendation serves both to prevent a first rupture and to rehabilitate a knee after knee arthroscopy surgery.