• Clinical science

Knee ligament injuries

Abstract

Knee ligament injuries are often the result of rotational movement of the knee joint (e.g., cutting and pivoting movements in sports). Injuries to the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL) result in knee pain and instability. Various maneuvers aid in demonstrating this knee instability and are usually sufficient for the diagnosis of collateral ligament tears. An MRI is the best confirmatory test for cruciate ligament tears. Isolated ligament injuries are usually treated conservatively, but surgery is recommended for complex injuries, severe knee instability, or patients with physically demanding occupations.

Anatomical overview

  • ACL and PCL connect the femur to the tibia
  • The MCL merges with the joint capsule of the knee
  • The LCL connects the femur and the fibula; it does not merge with the joint capsule of the knee

Anterior cruciate ligament injury

The anterior cruciate ligament is injured more commonly than the posterior cruciate ligament!

References:[1][2]

Posterior cruciate ligament injury

  • Mechanism of injury
    • Noncontact injury involving hyperflexion of the knee with a plantarflexed foot (seen in athletes)
    • Direct posterior blow to a flexed knee, seen in motor vehicle accidents (dashboard injury) or athletic contact injury
  • Clinical features
  • Diagnosis
  • Treatment
    • Conservative therapy for isolated injuries
    • Surgery for multiligament injuries, chronic knee instability, and for highly competitive athletes

References:[1][3][4]

Collateral ligament injury

Medial collateral ligament injury

  • Most commonly injured knee ligament
  • Mechanism of injury: valgus stress with possible external rotation
  • Clinical features
    • Knee swelling with ecchymosis (e.g., hemarthrosis), pain, deformity, and instability
    • Medial joint line tenderness
    • Valgus stress test
      • Medial joint laxity
      • The degree of joint laxity is graded based on the size of medial joint space during the valgus stress test; grade I: < 5 mm (mild instability), grade II: 5–9 mm (moderate instability), grade III: >= 10 mm (severe instability → other knee ligaments may be injured)
    • Frequently associated with medial meniscal tear
  • Diagnosis: An isolated MCL tear is a clinical diagnosis but x-rays and MRI can be used to rule out associated injuries
  • Treatment
    • Conservative (functional brace and physical therapy) for isolated MCL tears (grades 1–3)
    • Surgery if multiligament injury is present

Lateral collateral ligament injury

  • Isolated LCL injury is very rare; it is usually associated with a tear of the anterior and/or posterior cruciate ligaments, as well as the posterolateral corner (PLC)
  • Mechanism of injury: varus stress with possible external rotation .
  • Clinical features
    • Knee swelling with ecchymosis, pain, deformity, and instability
    • Lateral joint line tenderness
    • Varus stress test
      • Lateral joint laxity
      • The degree of joint laxity is graded based on the size of lateral joint space during the varus stress test; grade I: < 5 mm (mild instability), grade II: 5–10 mm (moderate instability), grade III: > 10 mm (severe instability → other knee ligaments may be injured)
  • Diagnosis: An isolated LCL tear is a clinical diagnosis, but x-rays and MRI can be used to assess for associated injuries.
  • Treatment
    • Conservative treatment (including a functional brace) for isolated LCL tears (grades I and II)
    • Surgery for PLC disruption (grade III)

MCL injuries are more common than LCL injuries!References:[5][6][7][8]