Knee ligament injuries

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.

• 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

• Higher incidence in females
• Mechanism of injury
  • Low-energy noncontact: sports injuries with a twisting mechanism, e.g., football, soccer, basketball, baseball, alpine skiing, and gymnastics
  • High-velocity contact injuries (less common): direct blows to the knee causing forced hyperextension or valgus deformity of the knee
• Clinical features
  • Audible pop followed by knee swelling (e.g., hemarthrosis), pain, and instability
    • Positive Lachman test (most sensitive test)
    • Positive anterior drawer test
    • Positive pivot shift test
  • Features of other ligamentous or meniscal injuries : The unhappy triad includes tears of the anterior cruciate ligament, medial collateral ligament, and the medial meniscus (i.e., tender joint line, poor knee extension)
• Diagnosis
  • Joint aspiration (in the case of severe joint effusion): hemarthrosis
  • MRI (confirmatory test)
• Treatment
  • Conservative treatment for mild knee instability, less physically demanding occupations, or premorbid inactivity
    • RICE protocol
    • Analgesia
    • Physical therapy
  • Arthroscopic surgery for multiligament injuries, chronic knee instability, and for highly competitive athletes
    • Allograft from achilles or patellar tendon
    • Postoperative care: knee brace, crutches, physical therapy
    • Double-bundle ACL graft using the semitendinosus and/or gracilis tendons (hamstring muscles)
    • ACL graft from the patellar tendon
• Complications
  • Meniscal degeneration
  • Osteoarthritis
  • Patella fracture
  • Patella tendon rupture
  • Reflex sympathetic dystrophy
  • Postoperatively: graft failure, graft impingement

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

References:^[1][2]

• 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
  • Initially vague symptoms: minimal (or absent) posterior knee pain, swelling, functional range of motion
  • Positive posterior drawer test
  • Positive posterior sag sign
  • Positive quadriceps active test
  • Positive posterolateral drawer test
• Diagnosis
  • X-rays initially; : bony avulsions and posterior sag of the tibia
  • MRI (confirmatory test)
• Treatment
  • Conservative therapy for isolated injuries
  • Surgery for multiligament injuries, chronic knee instability, and for highly competitive athletes

References:^[1][3][4]

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]