Meniscus tear

A meniscal tear can be caused by trauma or degenerative changes in the knee joint. Traumatic meniscal tears are usually associated with physical activity and typically result from rotation coupled with axial loading of the knee joint. 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 treatment (i.e., rest, ice, leg elevation, and analgesia) may be considered in small meniscal tears of the outer vascular zone and patients with pre-existing degenerative changes.

• Young, active patients: traumatic (i.e., axial loading and rotation action with a fixed foot during physical activity)
• Older patients: degenerative (e.g., continuous work in a squatting position)

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 meniscal tear (a combination of horizontal, longitudinal, and radial meniscal 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 may occur if the torn meniscus obstructs knee movement.
  • May hear clicking sound or have a popping or locking sensation
• 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

• X-ray : to exclude degenerative joint changes
• MRI: imaging modality of choice
  • Identifies the location and extent of meniscal tears
    • Hyperintense line in meniscus with possible distorted meniscal morphology
    • Empty groove in the case of bucket handle tears and double PCL sign
• Arthroscopy
  • Both diagnostic and therapeutic with a sensitivity and specificity of ∼ 100%
  • Diagnostic step of choice if MRI is contraindicated (e.g., patient with metal prostheses)

The differential diagnoses listed here are not exhaustive.

• Conservative treatment
  • Indication: pre‑existing degenerative changes in the knee joint (especially among older patients)
  • Approach
    • Rest, ice, and elevation of affected limb
    • Analgesia (NSAIDs)
    • Physical therapy (e.g., strengthening the quadriceps)
• Surgical treatment
  • Indication
    • Persistent disabling symptoms/effusions, functional limitations
    • Complex tears
  • Procedure
    • Arthroscopy
      • Partial meniscectomy: tears that cannot be repaired
      • Meniscal repair: fresh tears in the peripheral, vascular red zone (e.g., bucket handle tear near the base of the meniscus) can be sutured.
    • Meniscus transplantation
  • Postoperative care: physical therapy followed by gradual return to active physical activity.

• Osteoarthritis of the knee
• Baker cyst

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