Anatomy
The knee joint is made up of three bones: the femur, the tibia and the kneecap (patella). The kneecap, which lies in front of the joint, provides protection, among other things.
These bones are connected to each other by ligaments. There are 4 main ligaments in the knee, which act like strong straps (ropes) that hold the bones in place and stabilise the knee.
Collateral ligaments
As their name suggests, the collateral ligaments are located on the sides of the knee. The medial collateral ligament connects the femur to the tibia, while the lateral collateral ligament connects the femur to the fibula. Both control sideways movement of the bones and protect the knee from abnormal varus and valgus movements.
Cruciate ligaments
The cruciate ligaments are located inside the knee joint and cross each other, forming an X, with the anterior cruciate ligament at the front and the posterior at the back. With this arrangement they control the forward-backward movement and part of the rotational movement of the knee. In particular, the posterior cruciate ligament prevents the tibia from moving (sliding) backwards relative to the femur (thigh bone). It is stronger than the anterior cruciate ligament and is injured less often. It consists of two parts that combine in such a way as to form a structure about the size of a person’s little finger.
Description
An anterior cruciate ligament (ACL) tear is one of the most common ligament injuries of the knee. The incidence of ACL injuries in the USA is currently estimated at 200,000 per year, with 100,000 reconstructive operations. In general, ACL tears are more common in people who take part in “contact” or high-risk sports such as basketball, football, skiing, etc.
About 50% of ACL injuries occur together with damage to the meniscus, the articular cartilage or other structures of the knee. In addition, patients often have bone oedema (bone bruising) beneath the cartilage surface, an injury that is best seen on an MRI scan and may also indicate damage to the overlying articular cartilage.
Causes
It is estimated that 70% of ACL injuries are caused by non-contact mechanisms, i.e. without contact with another athlete, while 30% are the result of direct contact with another player.
The mechanism of injury often involves deceleration combined with a twisting movement of the knee, or an awkward landing on the leg.
Several studies have shown that, in certain sports, female athletes have a higher rate of ACL injury than male athletes. This is probably due to differences in fitness, muscle strength and neuromuscular control. Other suggested causes include the different alignment of the knee in women (Q angle) and the effects of oestrogens on the ligament.
At the moment of injury, the patient immediately feels sharp pain, followed by swelling of the joint (haemarthrosis), and has a feeling of instability, describing it as the knee “giving way”. Within a few hours the swelling makes the pain worse and makes it harder to bend and straighten the joint, so that standing and walking become quite difficult.
Clinical examination
At the initial assessment, the orthopaedic surgeon will request X-rays to rule out more serious injuries, such as a fracture of the upper end of the tibia (tibial plateau). In addition, if an ACL tear is suspected, the doctor may recommend an MRI scan to show the ACL, the menisci and the other ligaments of the knee in detail.
However, apart from the specialised imaging tests, the diagnosis of an ACL tear is essentially clinical and is based on a careful and detailed examination of the patient by the orthopaedic surgeon.
In a complete ACL tear, the examiner feels increased forward-backward movement of the tibia relative to the femur (especially compared with the healthy leg).
Another test for the ACL is the pivot shift test. In this test, the tibia starts out shifted forwards when the knee is fully straightened, and then moves backwards into the correct position relative to the femur when the knee is bent beyond 30 degrees.
Natural course after the injury
The natural course of an ACL injury without surgery varies from patient to patient and depends on the patient’s activity level, the degree of damage and the instability it causes.
The outlook for a partial ACL tear is often favourable, with a recovery and rehabilitation period of about 3 months. However, some patients with a partial tear have marked symptoms of instability and should be monitored regularly to assess the actual stability of the joint.
A complete ACL tear has a worse outlook. The instability of the knee is obvious and prevents the patient from taking part in sports that involve pivoting and loading the leg, while in some patients even walking is affected. On the other hand, there are reports of patients who continued to play sport without any symptoms of instability. This variability in symptoms is related to the severity of the original injury as well as to the patient’s physical demands.
About half of ACL injuries also involve damage to the meniscus, the articular cartilage or other ligaments. In addition, an ACL tear can cause secondary damage to the structures of the knee. Specifically, repeated episodes of instability cause some form of meniscal damage (90%) when patients are reassessed 10 years after the original injury. Similarly, damage to the articular cartilage of the knee occurs in 70% of patients after an ACL tear.
Non-surgical treatment
With conservative (non-surgical) treatment, progressive physiotherapy can help restore the knee to a large extent, up to its pre-injury condition. Through specific programmes, the patient can be trained to regain the stability of the joint. In addition, a functional brace or knee support can be used. However, many patients who choose conservative treatment go on to develop secondary knee injuries due to repeated episodes of instability.
In combined injuries (an ACL tear together with other knee injuries), surgical treatment is usually recommended, although this does not mean the patient cannot choose conservative treatment.
Non-surgical treatment of an isolated ACL tear is indicated for the following patients:
- Patients with a partial ACL tear and no symptoms of instability.
- Patients with a complete ACL tear and no symptoms of instability during low-demand sports activities
- Patients with light manual work and a sedentary lifestyle
- Children whose growth plates are still open.
Surgical treatment
After a tear, the ACL is not repaired by simply stitching it back together, as this has been shown to fail over time. Instead, the ligament is replaced with a tendon graft.
The grafts commonly used to replace the ACL include:
- Patellar tendon autograft (from the patient’s own body)
- Hamstring autograft
- Allograft (from a deceased donor) of the patellar, Achilles, semitendinosus, gracilis or tibialis posterior tendon.
Patients who underwent surgical ACL reconstruction showed long-term success rates of 82% to 95%. Recurrent instability and graft failure are seen in about 8% of cases.
The aim of surgery is to restore the ACL and the proper function of the ligaments, giving a stable knee that will allow the patient to return to sports activities. There are certain factors the patient should consider before deciding for or against surgery.
Considerations for the patient
Adult patients who take part in sports or jobs that require pivoting or sudden changes of direction, as well as those who do heavy manual work, should consider surgery. This group also includes older patients, because it is activity, not age, that determines the need for surgical treatment.
In adolescent patients, surgical ACL reconstruction may injure the growth plate, leading to problems with bone growth. For this reason, the orthopaedic surgeon may delay the operation until the child is closer to skeletal maturity, or modify the surgical technique to reduce the risk of injury to the growth plate.
A patient with an ACL tear and significant functional instability is at high risk of developing secondary knee damage and should therefore consider surgical ACL reconstruction.
In particular, ACL tears combined with injuries to the menisci (50%), the articular cartilage (30%) and the collateral ligaments are common. The so-called “unhappy triad” involves a tear of the ACL, the medial meniscus and the lateral collateral ligament. In all these cases of combined injuries, surgical reconstruction leads to better long-term results.
Surgical options
Patellar tendon autograft
During the procedure, the middle third of the patellar tendon is harvested together with the bone blocks at each end (tibia and kneecap). Some surgeons consider it the best graft for ACL reconstruction, mainly for high-demand athletes. In studies comparing the results of patellar tendon and hamstring grafts for ACL reconstruction, the graft failure rate was lower in the patellar tendon group (1.9% versus 4.9%). On the other hand, using the patellar tendon as a graft leads to a higher incidence of postoperative patellofemoral (front-of-knee) pain.
Possible problems after using the patellar tendon include:
- Postoperative patellofemoral pain
- Pain when kneeling
- A slightly increased risk of postoperative stiffness
- A slightly increased risk of kneecap fracture
Hamstring autograft
The semitendinosus tendon from the inner side of the knee is used to create the graft for ACL reconstruction. Sometimes the gracilis tendon, which lies next to the semitendinosus, is also used. In this way a “double- or quadruple-strand” graft is created. Surgeons who prefer hamstring grafts argue that there are fewer problems related to the donor site, including:
- Fewer problems with patellofemoral pain
- Less postoperative stiffness
- Smaller incisions
- Faster recovery
There is some evidence that patients with inherent ligamentous laxity and hyperextension of the knee may be at increased risk of postoperative graft laxity; for this reason, some colleagues recommend using the patellar tendon in these patients.
In addition, since the hamstrings provide dynamic support against valgus stress, some surgeons consider their use a contraindication in ACL reconstruction.
Allografts
Allografts are grafts taken from a deceased human donor, and they are becoming increasingly popular.
They are usually used in patients whose ACL reconstruction with autografts has failed, or in those who need more than one ligament reconstructed. The advantages of using an allograft include no pain from harvesting the graft, shorter operating time and smaller incisions.
However, allografts carry a risk of infection, including transmission of viruses (HIV and hepatitis C). Complications of this kind have led to improvements in the processing of allografts.
Surgery
Before surgery, the patient is referred for physiotherapy. Patients who have a stiff, swollen knee with limited range of motion may develop several postoperative problems. Usually, 3 to 4 weeks are needed between the time of injury and surgery.
Surgery usually begins with an examination of the patient’s knee while the patient is fully relaxed under anaesthesia. This final examination is used to confirm the ACL tear.
Depending on the case and the surgeon’s preference, the autograft is harvested (or thawed, if it is an allograft), and once it has been prepared, the surgeon inserts the arthroscope and instruments into the joint. After thorough cleaning, any meniscal damage is repaired.
With the most common ACL reconstruction techniques, bone tunnels are drilled in the tibia and the femur so that the graft can be placed in exactly the same position as the original ACL and, as far as possible, with the same direction and tension. Using sutures and a special needle, the graft is passed through the tunnels and fixed at the desired tension with an interference screw or staples. The materials used to secure the graft are not removed.
Variations in technique include different incisions and graft fixation materials, which vary according to the circumstances and the surgeon’s practice. Before the end of the operation, the surgeon checks the graft and makes sure its tension is correct. The wound is then closed in layers and bandaged. The patient is usually discharged the same day or the next day.
Surgical complications
- Infection. The incidence ranges from 0.2% to 0.48%. Bacterial infections have been reported after the use of allografts, mainly due to inadequate sterilisation technique.
- Transmission of viruses. Allografts are associated with an increased risk of transmitting viruses such as HIV and hepatitis C despite screening. Nevertheless, the estimated risk of HIV transmission from an allograft is less than 1 in 1,000,000.
- Bleeding, paraesthesia. Injury to the popliteal artery (0.01%) and paresis or paraesthesia of the limb have been reported very rarely.
- Thrombosis. As with any operation on the lower limbs, thrombosis is a real risk for the patient, estimated at 0.12%.
- Instability. Postoperative instability may occur due to a re-tear or reduced tension of the ACL graft, mainly due to poor or faulty technique (rates of 2.5% to 34% have been reported).
- Stiffness. Postoperative stiffness has been reported in 5% to 25% of cases.
Rehabilitation
Physiotherapy is an important part of recovery after ACL reconstruction, with exercises starting immediately after surgery. Much of the success of ACL reconstruction depends on the patient’s compliance with the intensive physiotherapy programme. With the newer surgical techniques mentioned above and stronger graft fixation, an accelerated rehabilitation programme is used.
Postoperative course: For the first 10-14 days after surgery, the wound is kept clean and dry, and the early emphasis is on regaining full extension and strengthening the quadriceps.
Ice therapy reduces swelling and pain, and a continuous passive motion machine (for bending and straightening the knee) may also be used. How much weight the patient can put on the leg is decided case by case.
Rehabilitation: The goals of rehabilitation include reducing swelling, maintaining mobility, restoring the full range of motion of the knee and strengthening the quadriceps muscle.
The patient can return to sport once the pain and swelling have completely subsided and full muscle recovery of the leg has been achieved. The sense of balance and proprioception of the joint return gradually, and using a functional brace or knee support can reassure the patient. The whole process takes 4 to 6 months, depending on the patient’s postoperative compliance and the surgical technique used.
Anterior cruciate ligament injuries of the knee
One of the most common knee injuries is a sprain or tear of the anterior cruciate ligament. Athletes who take part in high-demand sports, such as football and basketball, are at high risk of injuring their anterior cruciate ligament.
If the anterior cruciate ligament is injured, surgical treatment may be needed to restore the full range of motion of the patient’s knee. This will depend on factors such as the severity of the injury and the patient’s level of sports activity.
Anatomy
Three bones form the knee joint: the femur, the tibia and the kneecap (patella). The kneecap sits at the front of the joint and, together with the patellar tendon, forms part of the knee’s extensor mechanism. These bones are connected to each other by ligaments. There are 4 main ligaments in the human knee. They act like strong straps (ropes) that keep the bones in contact with each other and the knee stable.
Collateral ligaments
These are located on the sides of the knee. The medial collateral ligament is on the inner side of the knee and the lateral collateral ligament on the outer side. They control the sideways movements of the joint and protect it against extreme, abnormal movements.
Cruciate ligaments
These are located inside the knee joint. They cross each other in the shape of an X, with the anterior cruciate ligament at the front and the posterior at the back. The cruciate ligaments control the forward-backward movement of the knee. The anterior cruciate ligament runs diagonally inside the knee joint and prevents the tibia from sliding forwards in front of the femur. It also gives the knee rotational stability.
Description
In about half of cases, an anterior cruciate ligament injury is accompanied by injuries to other structures of the knee joint, such as the articular cartilage, the menisci and other ligaments.
Ligament injuries are considered “sprains” and are graded according to their severity.
Grade 1: The ligament is mildly injured. It may have been partly stretched, but it is still able to keep the knee joint stable.
Grade 2: In this type of sprain, the ligament is stretched to the point where it becomes looser. This is often referred to as a partial tear of the ligament.
Grade 3: This type of sprain is referred to as a complete tear of the ligament. The ligament is completely torn through and the knee joint becomes unstable. Partial tears of the anterior cruciate ligament are rare. Most tears are complete.
Causes
The anterior cruciate ligament can be injured in several ways:
- A sudden change of direction
- Stopping suddenly
- Slowing down abruptly while running
- Landing awkwardly from a jump
- A direct blow or collision, for example a tackle in football.
Several studies have shown that female athletes are more likely than male athletes in certain sports to injure the anterior cruciate ligament.
This is mainly due to differences in muscle strength, conditioning and neuromuscular control. Other factors include differences in the pelvis and in the alignment of the lower limbs, greater ligament laxity and the effect of oestrogens on the mechanical properties of ligaments.
Symptoms
When the anterior cruciate ligament is injured, a characteristic popping sound may be heard and the patient may feel that the knee has given way. Other typical symptoms include:
- Pain with swelling. The knee swells within 24 hours. If ignored, the swelling may go down on its own over a few days. However, returning to sport will reveal obvious instability of the knee, with a risk of injuring other structures of the joint (e.g. the menisci)
- Loss of full range of motion
- Pain and tenderness along the knee joint
- Pain when walking
Physical examination and medical history
At the first visit, the orthopaedic surgeon focuses on the patient's symptoms and medical history. During the clinical examination, the orthopaedic surgeon examines all the structures of the injured knee and compares them with those of the healthy leg. Most injuries can be diagnosed with a careful clinical examination.
Diagnostic tests
Other tests that help confirm the diagnosis are:
X-rays: Although they do not show the anterior cruciate ligament tear itself, X-rays can show whether the tear is associated with a bone injury.
MRI scan: Provides an accurate image of soft tissues such as the anterior cruciate ligament. However, an MRI is not always needed to diagnose an anterior cruciate ligament tear.
Treatment
Treatment of an anterior cruciate ligament tear depends on each patient's individual needs. For example, a young athlete involved in demanding sports will more often need surgery to return safely to sport. Less active, older patients can return to a less demanding everyday lifestyle without surgery.
Non-surgical treatment
A torn anterior cruciate ligament will not heal without surgery. However, non-surgical treatment may be the best option for older patients or patients with a low level of activity. If the overall stability of the knee has not been compromised, the orthopaedic surgeon may recommend simple, non-surgical options.
Brace: The orthopaedic surgeon may recommend a brace to protect the patient's knee from instability. For further protection, walking with crutches may be needed so that the injured leg does not bear weight.
Physiotherapy: As the swelling goes down, a carefully designed rehabilitation programme can begin. Specific exercises will restore function to the patient's knee and strengthen the muscles that support it.
Surgical treatment
In the vast majority of cases, the anterior cruciate ligament cannot be repaired simply with stitches. To reconstruct the ligament surgically and restore the stability of the knee, the surgeon uses tissue grafts from the patient's own body (autografts). These grafts act as a scaffold on which the new anterior cruciate ligament is rebuilt.
Grafts can be taken from several sources. Often part of the patellar tendon, which runs between the femur and the kneecap, is used. Sometimes grafts are taken from the hamstrings (“hamstrings”). The quadriceps tendon is used less often. Finally, allografts from deceased donors may also be used.
Each type of graft has advantages and disadvantages. This should be discussed with the orthopaedic surgeon so that the most suitable solution is found for each patient. Full recovery of the ligament takes time, and an athlete may need up to 6 months to return to sport.
The operation
Anterior cruciate ligament reconstruction is performed arthroscopically through very small incisions, which is why it is considered a minimally invasive method. The advantages of this method are a shorter hospital stay, less pain and faster recovery.
Anterior cruciate ligament reconstruction is not performed in the acute phase (immediately after the injury), unless the tear is part of a more complex injury. This delay allows the swelling to go down and the range of motion to return before surgery. In addition, immediate reconstruction of the anterior cruciate ligament increases the risk of arthrofibrosis, i.e. scar tissue forming in the joint, which leads to loss of knee range of motion.
Rehabilitation
Rehabilitation plays an important role in returning to everyday activities, whether treatment is surgical or non-surgical. A physiotherapy programme will help regain strength and range of motion.
In patients who have surgery, physiotherapy initially aims to restore the range of motion of the joint and of the surrounding muscles. This is followed by a stretching programme specially designed to protect the new ligament. The stretching programme gradually increases the load on the ligament. The final stage of rehabilitation aims at the athlete's functional return and is tailored to their needs.
Arthroscopic reconstruction for anterior cruciate ligament tear
As sports physician to major sports teams (Greek National Weightlifting Team, Esperos A1 Basketball, Ethnikos Asteras football in the A National Division, AGS Peristeri water polo in the A National Division, Greek National Karate Team, etc.) and doctor to top athletes, Professor Salmas has performed many anterior cruciate ligament reconstructions over the last 24 years, arthroscopically and with the modern endo button all-inside technique, which keeps incisions to a minimum as it is minimally invasive, using an autograft from either the patellar tendon or the hamstrings.
Description
Anterior cruciate ligament (ACL) tear is one of the most common ligament injuries of the knee. The incidence of ACL injuries in Greece is currently estimated at 5,000 a year, with 2,500 reconstruction operations. In general, ACL tears are more common in people who take part in “contact” or high-risk sports such as basketball, football, skiing, etc. About 50% of ACL injuries occur together with damage to the meniscus (meniscus tear), the articular cartilage (cartilage injury) or other structures of the knee. In addition, patients often have bone oedema (bone bruising) beneath the cartilage surface, which is best seen on an MRI scan and may also indicate injury to the overlying articular cartilage.
The doctor will examine your case and recommend the right treatment.
Request an appointment210 7793103Frequently asked questions
Anterior cruciate ligament tear: frequently asked questions
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Can I live without an anterior cruciate ligament?
Some less active patients manage well with physiotherapy. People who play sports involving changes of direction, or who feel their knee is unstable, usually need surgical reconstruction to protect the menisci and cartilage.
What graft is used?
Usually an autograft from the hamstring tendons or from the patellar tendon. The choice depends on the patient's age, sport and needs.
When can I return to sport?
Return to contact sports is usually possible 6–9 months after surgery, once the rehabilitation programme has been completed and the athlete has passed the appropriate functional tests.
Patient cases
Patients with an anterior cruciate ligament tear
ACL tear and medial meniscus tear – 12 years after ACL reconstruction
ACL tear with lateral and medial meniscus tears – knee arthroscopy – ACL reconstruction
ACL tear and medial meniscus tear – knee arthroscopy – ACL reconstruction and partial meniscectomy, 10 years after surgery
Meniscus tear – ACL tear – ACL reconstruction – arthroscopic meniscal repair
ACL and PCL tears with a meniscus tear – ACL and PCL reconstruction
Knee ACL tear with associated medial meniscus tear – 3 months after surgery
ACL tear – knee arthroscopy – ACL reconstruction – 12 years after surgery
ACL tear – knee arthroscopy – ACL reconstruction – 12 years after surgery
ACL tear – ACL reconstruction – 20 days after surgery
ACL tear – ACL reconstruction
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