Meniscus tear

A meniscus tear can be caused by trauma or degenerative changes in the knee joint. Traumatic meniscus tears are usually associated with physical activity and typically result from rotation coupled with axial loading of the knee joint. Degenerative tears are typically caused by overuse or chronic stress-induced joint deterioration. The affected meniscus may be medial or lateral, with the medial frequently torn because of its relative immobility. Clinical features include pain and limited range of movement of the affected knee. Key features are slow onset joint effusion and a characteristic popping or clicking sensation during joint maneuvers. MRI is used to confirm the diagnosis. Arthroscopy enables simultaneous surgical intervention, especially in patients with persistent symptoms, inner zone tears, and functional limitations. Conservative management (including use of a knee brace, rest, leg elevation, and analgesia) is typically appropriate for simple tears and patients with preexisting degenerative changes.

• Traumatic meniscus tear
  • Caused by an acute injury, most often due to axial loading and rotation with a fixed foot
  • Typically affects young, active individuals
• Degenerative meniscus tear
  • Caused by overuse or chronic stress-induced joint deterioration, e.g., continuous work in a squatting position
  • Typically affects older individuals
  • Often associated with degenerative joint disorders (e.g., osteoarthritis) ^[1]

A meniscus tear may be medial or lateral. The medial meniscus is more commonly injured than the lateral meniscus.

• Location of the tear
  • White zone: inner third, avascular area
  • Red-white zone: middle third, poorly vascularized area
  • Red zone: outer/peripheral third, vascularized area
• Type of tear
  • Longitudinal tear (vertical tear): perpendicular to the tibial plateau
  • Radial tear: perpendicular to the tibial plateau and the longer axis of the meniscus
  • Horizontal tear: parallel to the tibial plateau
  • Displaced tears
    • Bucket handle tear: displaced and extensive longitudinal tear that splits the meniscus into two parts that remain connected at the anterior and posterior ends
    • Parrot beak tear: displaced radial tear
    • Flap/oblique tear: displaced longitudinal or horizontal tear
  • Simple or complex meniscus tear (a combination of horizontal, longitudinal, and radial meniscus tears)

• Knee pain: exacerbated by weight‑bearing or physical activity
• Joint line tenderness (medial or lateral)
• Restricted knee extension with possible knee instability
  • Locked knee: springy resistance to active and passive knee extension, typically caused by a torn meniscus obstructing knee movement
  • A clicking sound and/or a popping and locking sensation may be present on movement.
• Intermittent joint effusions
  • Tears in the medial, white zone → serous effusion
  • Tears in the red zone near the base of the meniscus → bloody effusion (hemarthrosis)
  • Patellar tap test: a maneuver used to assess knee joint effusion
    • Procedure
      • Patient lies in a supine position with the knee in full extension
      • The examiner applies pressure to the thigh toward the proximal part of the knee and to the lower leg, directly below the patella
      • While maintaining this position, the examiner gently presses down on the patella.
    • Findings
      • Positive test: A floating or swimming patella that can be pressed down toward the femur, resulting in a palpable tap, suggests a knee effusion.
      • Negative test: if no effusion is present, then the patella is located directly on the femur and cannot be displaced

Clinical evaluation ^[3]

• Patients with acute injury, pain, and/or swelling: Follow the approach to acute internal knee derangement.
• Patients without significant swelling or uncontrolled pain
  • Perform an orthopedic examination of the knee to identify clinical features of meniscus injury. ^[3]
  • Include provocative tests for meniscus injury, e.g., the McMurray test. ^[3]

A clinical diagnosis of meniscus tear can be made if multiple provocative tests are positive, knee joint effusion is present, and a full knee x-ray series is normal. ^[3]

Imaging ^[4]

• Full knee x-ray series: initial imaging to exclude fractures ^[4]
• MRI: imaging modality of choice to identify the location and extent of meniscus tears and any concomitant knee ligament injuries
  • Indications ^[5][6]
    • Athletic adults < 40 years of age with posttraumatic locked knee and suspected meniscus tear
    • Persistent symptoms after 4–6 weeks of conservative management
    • Planning for arthroscopic intervention
    • Consider for uncertain diagnosis after clinical evaluation. ^[6]
  • Findings ^[7][8]
    • Hyperintense line in meniscus with possible distorted meniscal morphology
    • Bucket handle tear: signs include the double posterior cruciate ligament sign
• Ultrasound
  • Formal musculoskeletal (MSK) ultrasound by an experienced practitioner has an accuracy similar to that of MRI. ^[9]
  • MSK point-of-care ultrasound can help identify joint effusion.

Arthroscopy

• A dual diagnostic and therapeutic procedure; diagnostic reference standard ^[7]
• Can be used as an alternative diagnostic test in patients with MRI contraindications
• Generally only performed in conjunction with arthroscopic treatment ^[10]

The differential diagnoses listed here are not exhaustive.

For initial management of acute traumatic knee swelling, see “Acute internal knee derangement.”

Conservative management ^[11]

• Indications
  • Initial management for all patients with suspected meniscus injury
  • Degenerative meniscus tears
  • Simple traumatic meniscus tears
• Components
  • Rest, ice, and elevation of the affected limb
  • Analgesia (NSAIDs)
  • Knee brace
  • Activity modification
  • Physical therapy (e.g., strengthening the quadriceps)

Manage simple traumatic meniscus tears and degenerative meniscus tears conservatively for at least 4–6 weeks before considering treatment escalation. ^[11]

Surgical treatment ^[1][11]

The decision to operate is made by an orthopedic surgeon and based on patient factors and available resources.

• Relative indications ^[1][11]
  • Traumatic meniscus tear (especially with injury onset < 6 weeks) ^[11][12]
  • Tear involving the vascular red zone
  • Complex meniscus tear > 1 cm
  • Patients < 40 years of age
  • Athletic adults
  • Concomitant ACL injury
  • Locked knee
  • Severe persistent functional impairment
• Contraindication: degenerative meniscus tear ^[1]
• Procedures: Arthroscopy is performed more commonly than open surgery.
  • Meniscus repair: usually preferred ^[11][13]
  • Partial meniscectomy: only in select cases ^[11]
  • Meniscus reconstruction with or without allograft: rare
• Postoperative care: physical therapy, rehabilitation, and gradual return to activity

• Osteoarthritis of the knee
• Baker cyst

We list the most important complications. The selection is not exhaustive.