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Meniscus Tear

  • A meniscus tear is an acute or degenerative injury to the meniscal fibrocartilage of the knee.
  • Classification:
    • Acute tear:
      • Longitudinal (50-90%)
      • Radial (6%)
      • Flap (4%)
    • Degenerative tear:
      • Mostly horizontal cleavage or complex tears
  • Acute tears occur mainly in adolescents and young adults, and degenerative tears predominate in the 40-60-year-old population.
  • Degenerative medial tears occur more frequently than do degenerative lateral meniscal tears.
  • Acute lateral meniscus tears occur more frequently than do acute medial tears.
  • In 1 study of asymptomatic individuals, MRI showed that 13% of those <45 years old and 36% of those >45 years old had a meniscus tear.
  • Another study showed that 60% of cadavers aged 65 years at time of death had degenerative tears.
  • Concomitant ACL tear occurs in ~30% of patients with acute meniscus tears.
Risk Factors
  • Twisting, hyperflexion injury
  • Age >40 years
  • Chronic ACL deficiency
  • Tibial plateau fracture
  • Arthritis affecting the knee
No Mendelian inheritance is known.
  • Acute:
    • Often occurs during athletic activities, most commonly football, basketball, and wrestling
    • A common mechanism is a severe twisting at the knee, often during change of direction.
    • Can be associated with ACL injury
  • Degenerative:
    • Age-related breakdown of collagen fibers
Associated Conditions
Ligamentous injury (ACL, collateral ligament) in acute tears
Signs and Symptoms
  • Acute pain and swelling
  • Tenderness localized to the joint line or popliteal region with the knee flexed
  • Popping, locking, catching, or buckling with large, unstable the tears
  • Inability of the patient to extend the knee fully in the presence of a displaced bucket-handle tear
  • May have chronic mild swelling and joint-line pain in the presence of a degenerative tear
  • Acute twisting of the knee while weightbearing
  • Chronic knee pain
Physical Exam
  • Assess knee stability.
  • Joint-line tenderness is the best clinical sign (74% sensitivity, 50% positive predictive value).
  • McMurray test:
    • Hyperflex the knee and gently rotate it internally and externally, applying valgus and varus stress while extending the knee.
    • May feel click, pop, or crepitance
    • Reproduces patient symptoms
  • Apley grind test:
    • Position the patient prone.
    • Internally and externally rotate the leg with traction and compression.
    • Pain or mechanical symptoms indicate likely meniscal pathology.
  • Plain radiographs: 30° flexed posteroanterior view is best for observing weightbearing surfaces.
  • MRI is 90-98% accurate, although it can give false-positive results.
Diagnostic Procedures/Surgery
Arthroscopy is the gold standard for diagnosis.
Pathological Findings
  • Collagen fibers:
    • Oriented circumferentially
    • Resistant to compressive forces
    • May tear under shear stress
  • Tears in inner 2/3 heal poorly because of the lack of blood supply.
  • Degeneration from repeated microtrauma occurs, with gradual loss of collagen and integrity that leads to tears.
Differential Diagnosis
  • Chondral lesion
  • ACL or collateral ligament tear
  • Fibrotic plica
  • Fat-pad impingement
  • Osteoarthritis
  • Patellofemoral chondrosis
  • Spontaneous osteonecrosis
General Measures
  • Begin with a trial of rest, protected weightbearing, and modified activity.
  • If the patient remains symptomatic, offer MRI or arthroscopic evaluation.
  • Weightbearing as tolerated
  • Often return to full activities 2-3 weeks after injury
Drugs of choice are analgesics or NSAIDs.
  • Indications for arthroscopy:
    • Symptoms that affect activities of daily living or work, mechanical symptoms
    • Positive physical findings (joint tenderness, effusion)
    • Failure of nonsurgical treatment
  • The following lesions should be repaired:
    • Complete vertical tear >10 mm long
    • Tear within the peripheral 10-30% of the meniscus or 3-4 mm of the meniscocapsular junction
  • Better healing of meniscal repairs with concurrent ACL reconstruction
  • Complex tears and those in the avascular inner 2/3 are resected.
  • Total meniscectomy is not recommended because of the increased risk of degenerative arthritis.
  • Initiate gradual strengthening and ROM program.
  • Return to full activities 6-8 weeks after partial meniscectomy
  • Complications are uncommon but include:
    • Injury to neurovascular structures (infrapatellar branch of saphenous nerve, causing pain, dysesthesias at the portal site)
    • Infection
    • DVT
    • Arthritis
836.2 Meniscus tear
Q: When can I walk after an arthroscopic meniscectomy?
A: For an isolated arthroscopic partial meniscectomy, weightbearing as tolerated can begin almost immediately.
Q: What decides if a meniscus tear is repaired?
A: The decision is based on the capacity to heal, i.e., the presence of a blood supply. Acute tears, near the periphery, usually are repaired. Less peripheral and degenerative tears are resected.

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