Updated: 11/30/2019

Meniscus Tear

Review Topic
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  • A 25-year-old woman twisted and injured her right knee during a soccer game 4 weeks ago. At that time, there was moderate knee swelling which has since resolved. She reports intermittent medial right knee pain and a sensation of the joint giving way since then. Her symptoms are aggravated by twisting or squatting. On physical exam, there is a mild effusion, medial joint line tenderness, and a positive medial McMurray test. Valgus stress reveals no pain or joint opening. Anterior and posterior drawer test is negative.  
  • Clinical definition
    • a knee injury caused by meniscal tears, categorized into two types
      • acute meniscus tear
      • age-related degeneration of meniscus
    •  part of the "terrible triad"
      • anterior cruciate ligament tear
      • medial collateral ligament tear
      • meniscus tear
  • Epidemiology
    • demographics
      • male > female
      • < 40 years of age are more likely to have acute tears
      • > 40 years of age are more likely to have degenerative tears
      • medial meniscus tears are more common than lateral meniscus tears
        • due to decreased mobility of the medial meniscus as it attaches to the MCL
    • location
      • menisci are located between the femoral condyles and tibial plateau
    • risk factors
      • acute tears
        • sports
      • degenerative tears
        • older age
        • male gender
        • work-related use of knee (kneeling, squatting, and stair climbing)
      • obesity
  • Pathogenesis
    • two most common mechanisms
      • non-contact trauma from twisting of the knee or sudden acceleration and directional change, often in the context of sports
      • contact injury with varus or valgus forces on the knee
      • repetitive normal forces from age-related degeneration
        • menisci are less compliant with increasing age
  • Associated conditions
    • > 30% associated with anterior cruciate ligament injury
  • Symptoms
    • persistent joint pain after inciting event (acute tears)
    • insidious onset of knee pain (degenerative tears)
    • locking, popping, or catching of the knee during ambulation
      • pain during ambulation, especially with climbing stairs
    • sensation of joint giving way
  • Physical exam
    • knee effusion and swelling that worsens with activity
      • more common with acute injuries
    • knee pain that worsens with motion, especially with deep knee flexion
    • impaired range of motion
    • focal joint tenderness
    • normal patellar tracking
    • positive McMurray test 
      • for medial meniscus tear
        • flex the knee and palpate medial side of the knee
        • externally rotate the leg and bring the knee into extension
        • palpable pop or click is a positive test 
      • for lateral meniscus tear
        • flex the knee and palpate lateral side of the knee
        • internally rotate the leg and bring the knee into extension
        • palpable pop or click is a positive test
  • Radiograph
    • indications
      • to rule out other bony pathologies
    • findings
      • typically normal
      • may show secondary findings such as joint effusion
  • Magnetic resonance imaging
    • indications
      • to confirm a meniscus tear when the diagnosis is unclear
    • findings
      • hyperintense signal inside the meniscus
  • Making the diagnosis
    • most cases are clinically diagnosed
  • Anterior or posterior cruciate ligament injury
    • distinguishing factor
      • positive drawer sign
  • Osteoarthritis of the knee
    • distinguishing factor
      • no diffusion present
      • joint stiffness is typically present
  • Management approach
    • meniscal tears can be managed conservatively or with surgery and depends on various patient factors, including the patient’s age, the presence of comorbidities, and extent of the tear
  • Conservative
    • conservative treatment
      • indications
        • degenerative tears
        • asymptomatic tears
        • patients with multiple comorbidities and poor surgical candidates
      • modalities
        • rest and ice
        • use of crutches
        • knee sleeves
        • physical therapy
  • Medical
    • nonsteroidal anti-inflammatory drugs
      • indications
        • pain management
  • Operative
    • arthroscopic repair
      • indications
        • symptomatic tears
        • failure of conservative management
      • surgeries
        • partial meniscectomy
        • meniscal repair
  • Fibrosis
  • Septic arthritis

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Questions (3)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2

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(M2.OR.4759) A 25-year-old male wrestler presents to his primary care physician for knee pain. He was in a wrestling match yesterday when he was abruptly taken down. Since then, he has had pain in his left knee. The patient states that at times it feels as if his knee locks as he moves it. The patient has a past medical history of anabolic steroid abuse; however, he claims to no longer be using them. His current medications include NSAIDs as needed for minor injuries from participating in sports. On physical exam, you note medial joint tenderness of the patient’s left knee, as well as some erythema and bruising. The patient has an antalgic gait as you observe him walking. Passive range of motion reveals a subtle clicking of the joint. There is absent anterior displacement of the tibia relative to the femur on an anterior drawer test. The rest of the physical exam, including examination of the contralateral knee is within normal limits. Which of the following structures is most likely damaged in this patient? Review Topic | Tested Concept

QID: 109014

Medial meniscus




Lateral meniscus




Medial collateral ligament




Lateral collateral ligament




Anterior cruciate ligament



M2 D

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