What are the characteristics of a meniscus injury?

Characteristics of Meniscus Injury

Meniscus tears are common, usually incidental findings that may or may not be the cause of knee pain, and often present with mechanical symptoms including pain, swelling, and limited function. 1

Clinical Presentation

Symptoms

• Joint line pain (medial or lateral depending on which meniscus is injured)
• Mechanical symptoms:
  • Clicking
  • Locking
  • Catching
  • Giving way
• Swelling (effusion)
• Limited range of motion
• Inability to fully extend the knee in cases of displaced bucket-handle tears

Mechanism of Injury

• Traumatic tears:
  • Sudden knee flexion with internal or external rotation component 2
  • Acute twisting trauma to the knee 1
  • Fall with rotational force
  • Sports-related injuries, especially in younger patients
• Degenerative tears:
  • Older patients often present without specific mechanism of injury 2
  • Part of degenerative knee disease process
  • Associated with osteoarthritic changes

Anatomical Considerations

• Medial meniscus:

  • More vulnerable to injury due to intimate attachment to medial collateral ligament 2
  • Less mobile than lateral meniscus
  • More commonly torn than lateral meniscus

• Lateral meniscus:

  • More mobile and less prone to tears
  • Often injured in conjunction with ACL tears 2
  • Better healing potential due to greater vascularity

Types of Meniscal Tears

• Vertical/longitudinal tears (including bucket-handle)
• Horizontal/cleavage tears
• Radial tears
• Complex/degenerative tears
• Root tears (affect meniscal hoop function and accelerate cartilage degeneration) 3

Diagnostic Evaluation

Physical Examination

• Joint line tenderness (highly sensitive)
• Presence of knee effusion
• Special tests:
  • McMurray test
  • Apley test
  • "Bounce home" test 2
  • Thessaly test

Imaging

• MRI: Test of choice for confirming meniscal injury 2

  • Defines type, location, and severity of tear
  • Highly accurate for evaluating bone marrow contusions, occult fractures, and ligamentous injuries 1
  • Superior to CT for meniscal evaluation 1

• Radiographs:

  • Initial imaging for acute knee trauma
  • May not show meniscal tears directly
  • Rule out fractures and assess for osteoarthritis

• Ultrasound:

  • Limited role in meniscal tear diagnosis
  • Can detect joint effusion and some meniscal tears
  • Reported sensitivity of 85-88% and specificity of 86-90% for meniscal tears 1

Healing Potential Based on Location

• Red-Red Zone (outer third):

  • Well-vascularized
  • Good healing potential 2
  • May respond to conservative management

• Red-White Zone (middle third):

  • Limited vascularity
  • Variable healing potential

• White-White Zone (inner third):

  • Avascular
  • Poor healing potential 4
  • Often requires surgical intervention

Management Considerations

Conservative Management

• Appropriate for minor tears, especially in degenerative knees 5
• Initial focus on reducing swelling and pain
• Rehabilitation emphasizing tri-planar functional retraining 2
• Progressive return to sports or work-specific activities

Surgical Management

• Meniscal repair:

  • Preferred over meniscectomy to prevent premature osteoarthritis 2
  • Better long-term outcomes and less severe degenerative changes compared to partial meniscectomy 3
  • Higher reoperation rates compared to meniscectomy
  • Techniques include "inside-out," "outside-in," and "all-inside" approaches 3

• Partial meniscectomy:

  • For irreparable tears
  • Increased risk of subsequent development of degenerative changes 5
  • Most common arthroscopic knee procedure 6

Important Clinical Pitfalls

1. Incidental findings: Meniscus tears are common, often incidental findings that may not be the cause of knee pain, especially in older patients with degenerative changes 1

2. Recovery expectations: Recovery from arthroscopic surgery typically takes 2-6 weeks, with limitations on weight-bearing in the first week 1

3. Misdiagnosis: Not all knee pain is due to meniscal tears; other conditions like osteoarthritis may be the primary cause of symptoms

4. Overtreatment: Arthroscopic surgery for degenerative meniscal tears shows only modest probability (<15%) of small improvement in short-term pain and function that does not persist to one year 1

5. Locked knee: True locked knee (objectively unable to fully extend) may require prompt surgical intervention 1

Understanding these characteristics of meniscal injuries is crucial for appropriate diagnosis and management decisions that prioritize long-term knee health and function.