The anterior cruciate ligament or ACL plays a crucial role in the knee’s stability. An injury to this ligament can lead to significant instability, affecting not only mobility but also quality of life. Knee specialist Professor Cavaignac provides information on the structure, function, and injuries of the ACL.
Definition and Anatomy of the ACL
The ACL is located in the centre of the knee joint. It connects the femur to the tibia and is critical for stabilising the joint by preventing anterior displacement of the tibia relative to the femur.
Structure and Function
Anatomically, the ACL crosses the knee diagonally and, together with the posterior cruciate ligament (PCL), forms a cross. It limits excessive movements by providing an anchoring point between the tibia and the femur. It plays an essential role in activities such as running, jumping, and pivoting movements. An anterior cruciate ligament tear can be painful and significantly disrupt daily life.
Symptoms of an ACL injury
Depending on the type of anterior cruciate ligament injury , symptoms and their intensity can vary. However, the most common symptom of any type of ACL injury is that patients feel severe pain when the injury occurs. This can cause them to stop the activity immediately. A “pop” or cracking sound may also occur, indicating a more severe injury to the ACL.
The inflammation caused by the injury can lead to swelling around the knee within hours.
Mobility is significantly reduced due to pain in the knee.
Patients often describe a sensation of the knee “giving way” when walking or changing directions. This sensation happens because the knee’s stabilisation mechanism is damaged. In some cases, it is difficult to put weight on the affected leg.
Depending on the severity of the ACL injury, the symptoms will be more or less pronounced.
Without treatment, an ACL injury can lead to chronic instability, increasing the risk of damage to other knee structures such as the meniscus and articular cartilage. This can lead to the onset of early osteoarthritis. Therefore, it is important to consult a specialist as soon as possible if you have symptoms of an ACL injury.
Meniscal injuries associated with ACL rupture
The menisci play a key role: they distribute loads and provide secondary stability (additional stabilisation to ligament function).
When the ACL is torn, the resulting anteroposterior instability (abnormal forward–backward movement of the tibia) and rotational instability expose the menisci to abnormal stresses, promoting secondary meniscal injuries.
This illustration shows that in more than 75% of ACL ruptures, other knee structures such as the anterolateral ligament or meniscal roots are also damaged, which justifies their systematic assessment and treatment during surgery.
How are they diagnosed?
During surgery, Professor Cavaignac always performs a complete diagnostic arthroscopy (a mini-camera exploration of the knee) to assess both menisci.
Depending on the type and location of the lesion, he favours repair by suturing in order to preserve the meniscal tissue as much as possible and reduce the risk of osteoarthritis. If repair is not possible, a partial meniscectomy (removing only the damaged portion) is performed to preserve the largest possible functional surface.
Frequency of associated lesions observed by Professor Cavaignac:
- Posterior horn tears of the medial meniscus: ~22% of ACL ruptures (often ramp lesions)
- Lateral meniscus root tears: ~15% of ACL ruptures
Ramp lesions
Ramp lesions are tears located at the back of the medial meniscus. They help control anterior translation of the tibia. If left unrepaired, they can lead to persistent instability.
Repair: posteromedial approach with hook suture. This method allows:
- Direct access to the injured area (posterior horn of the medial meniscus)
- A more precise anatomical repair
- A reduced risk of poor tension or incorrect orientation of sutures, which may occur with the all-inside horizontal technique (top diagram).
Lateral meniscus root
When this area is damaged, the meniscus loses its ability to cushion and stabilise the knee.
Repair: fixation through transosseous tunnels or “all-inside” sutures, depending on the lesion. Professor Cavaignac has published a specific study on this technique, Evaluation of the All-Inside Technique for the Repair of Lateral Meniscus Root Tears at 1 Year After ACL Reconstruction, which analyses one-year outcomes and confirms the reliability of this approach.
Meniscectomy: a solution to be considered with caution
When meniscal repair is not possible (tissue too damaged or poorly vascularised), a partial meniscectomy may be performed. This consists of removing only the injured portion of the meniscus, preserving as much healthy tissue as possible to reduce the risk of osteoarthritis.
However, scientific data show that meniscectomy can have long-term consequences:
- In professional athletes, it is associated with shorter careers and fewer games played.
- For muscle function, it does not significantly delay return to sport compared with repair, but it causes permanent loss of meniscal tissue, with an increased risk of early cartilage wear.
Professor Cavaignac always prioritises repair whenever possible and resorts to meniscectomy only as a last option, and then in the most limited form possible.
Causes and Mechanisms of ACL Injury
An anterior cruciate ligament (ACL) rupture usually occurs during activities that involve sudden stops, rapid changes of direction, or a direct impact to the knee, like in contact sports.
Mechanisms of Injury
- Hyperextension: Overextension of the knee beyond its normal capacity
- Excessive Rotation: Twisting of the knee while the foot is fixed on the ground
- Direct Impact: Direct blow to the knee, often seen in sports collisions
Predisposing Factors
Certain factors increase the risk of ACL injury, including anatomical and behavioural considerations.
Risk Factors
- Gender: Women are more likely than men to sustain ACL injuries due to anatomical and hormonal differences.
- Muscle Imbalances: Weakness in the muscles surrounding the knee can increase the risk.
- Sports Practices: Participating in sports that require movements that stress the ACL, such as football, skiing and basketball.
Preventing ACL Injuries
To prevent ACL injuries, strengthening exercises, proprioception training, and appropriate sports technique can help to reduce the stress placed on the ligament.
Prevention Strategies
- Muscle Strengthening: Focus on muscles that stabilise the leg
- Education and Training: Programmes aimed at improving technique and movements during sports activities
By strengthening the stabilising muscles and improving your technique, the risk of ACL injuries can be reduced.
Protecting the ACL is essential to maintaining knee function and to participating in many activities. A thorough understanding of the structure, functions, risks, and prevention strategies can help reduce the risk of ACL injuries.