The knee ligaments (cruciate and collateral)

The knee joint is primarily stabilized by four ligaments :

• The anterior cruciate ligament (ACL)
• The posterior cruciate ligament (PCL)
• The medial collateral ligament (MCL)
• The lateral collateral ligament (LCL)

During knee trauma, these ligaments can be stretched, partially, or completely torn (severe sprain). Management will depend on the severity of the ligament injury and the presence or absence of associated lesions (meniscus and cartilage). Treatment can be conservative, with or without immobilization in a brace for several weeks, or surgical, involving repair or reconstruction of the affected ligament(s).

a. Anterior Cruciate Ligament (ACL)
The ACL is crucial for knee stability, preventing the tibia from moving forward and rotating inward relative to the femur. Most ACL tears occur in individuals participating in sports involving sudden stops and changes in direction: football, basketball, skiing, etc.
Rupture is rarely partial and is most often complete or nearly complete. It is frequently accompanied by meniscal lesions (~30%), rupture of the anterolateral ligament (~90%), or medial collateral ligament rupture (~30%).
Depending on the type of rupture and associated lesions, the ACL may not heal properly. The patient may then feel varying degrees of knee instability, ranging from difficulty in resuming sports activities to discomfort in daily life with episodes of knee giving way. In the short and medium term, this laxity leads to new meniscal lesions or worsens existing ones. In the long term, it can result in early osteoarthritis.
Functional treatment with physiotherapy and sports medicine follow-up is proposed in cases of mild laxity, without significant meniscal lesions and/or in the absence of high-risk activities.
Surgery is proposed based on the following factors: age, feeling of instability, the degree of laxity on clinical examination, associated lesions (menisci, cartilage, and other ligaments), and the desire to participate in pivot sports (sports involving direction changes).
For more details on the anterior cruciate ligament:
Public conference on December 3, 2020: Link
Link to the patient information brochure: ACL Reconstruction

b. Posterior Cruciate Ligament (PCL)
The PCL prevents the tibia from sliding backward relative to the femur. It is the strongest ligament in the knee, which is why its rupture is less common. The lesion can be partial, complete, or associated with tears of other ligaments. Isolated lesions can be treated conservatively with a brace. Surgery is indicated later if instability persists. Surgery may be immediately proposed depending on activity level, age, type of lesion (bony avulsion), and in the presence of associated injuries.

c. Medial Collateral Ligament (MCL)
MCL injury is generally treated without surgical intervention unless there is a bony avulsion or it is associated with other ligament injuries.

d. Lateral Collateral Ligament (LCL)
Complete and isolated LCL tears are rare. These are most often complex injuries involving other structures (posterolateral corner, popliteal tendon, cruciate ligaments) and are generally treated surgically.

e. Multiligamentous Injuries or Knee Dislocation
These are rare but very serious injuries. Up to 30% of cases involve injury to the fibular nerve and/or the popliteal artery. Treatment is most often surgical, with repair and/or reconstruction of all affected ligaments, if possible, within 10-21 days after the accident.