Knee Ultrasound

Aka: Knee Ultrasound

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II. Images

  1. usKnee_AntLongInfrapatellar.png
  2. usKnee_AntLongSuprapatellar.png
  3. usKnee_AntTransFemCondyles.png
  4. usKnee_LatLongLCL.png
  5. usKnee_MedialLongMCL.png

III. Indications

  1. Dynamic tendon evaluation (e.g. Patellar tendon, quadriceps tendon)
  2. Collateral ligament evaluation
  3. Baker Cyst
  4. Neurovascular evaluation
  5. Knee Effusion evaluation (esp. to direct needle aspiration)

IV. Technique: Anterior Knee Ultrasound

  1. Positioning
    1. Patient lies supine with knee flexed 20 degrees over towel roll
  2. View 1: Long Axis (LAX) with indicator towards proximal leg (hip)
    1. Superior aspect (suprapatellar)
      1. usKnee_AntLongSuprapatellar.png
      2. Superficial structures
        1. Quadriceps tendon
          1. Hypoechoic at Patellar insertion (rotate or tilt probe to visualize)
        2. Patella
      3. Mid-structures
        1. Suprapetellar recess
        2. Suprapatellar fat pad (surrounded by small amount of fluid in suprapatellar bursa)
      4. Deep structures
        1. Prefemoral fat pad (overlies femur)
        2. Femur
    2. Inferior aspect (infrapatellar)
      1. usKnee_AntLongInfrapatellar.png
      2. Superficial structures
        1. Patella
        2. Superficial subcutaneous bursa (proximal, adjacent to Patella)
        3. Patellar tendon
      3. Mid-structures
        1. Infrapatellar bursa (distal, adjacent to tibia)
        2. Infrapatellar fat pad (Hoffa's fat pad)
      4. Deep structures
        1. Femoral condyle
        2. Tibia
  3. View 2: Short Axis (SAX)
    1. Start at distal thigh (where each of four quad Muscles are visible)
    2. Slide probe inferiorly down the anterior knee
      1. Quadriceps tendon
      2. Suprapatellar bursa (to either side of tendon)
      3. Patella
      4. Femoral trochlear cartilage (with hyaline cartilage)
        1. Appears as two parallel lines
        2. Best evaluated with knee in 90 degree flexion with suprapatellar approach directed under Patella
      5. Infrapatellar bursa (to either side of tendon)
      6. Patellar tendon
    3. Images
      1. usKnee_AntTransFemCondyles.png
    4. Clinical indications
      1. Directs Knee Aspiration by identifying largest fluid pocket and guiding needle entry

V. Technique: Medial Knee Ultrasound

  1. Positioning
    1. Patient lies supine with knee flexed 20 degrees over towel rolll (as with anterior Knee Exam)
    2. Leg external rotation improves access to medial compartment
  2. Images
    1. usKnee_MedialLongMCL.png
  3. Components
    1. Superficial structures
      1. Medial collateral ligament
      2. Medial patellofemoral ligament (MPFL)
        1. Tears with Patellar Dislocation
      3. Pes anserine bursa
        1. Difficult to visualize
        2. Lies immediately superficial to medial collateral ligament at distal aspect
    2. Mid-structures
      1. Medial meniscus
        1. Suboptimal evaluation (poor sensitivity for pathology compared with gold standard MRI)
        2. Peripheral meniscal tear may be visualized
    3. Deep structures
      1. Distal femur and medial femoral condyle
      2. Proximal tubia

VI. Technique: Lateral Knee Ultrasound

  1. Positioning
    1. Patient lies supine with knee flexed 20-30 degrees over towel roll (as with anterior Knee Exam)
    2. Start with probe in long axis (LAX) anteriorly over the Patellar tendon in the infrapatellar region (as above)
      1. Slide the probe laterally observing the femur margin as it elongates over the length of the screen
  2. Images
    1. Anatomy ("Z" of the ITB, LCL and Biceps Femoris)
      1. orthoLateralKneeZ.png
    2. Ultrasound
      1. usKnee_LatLongLCL.png
  3. Approach
    1. IT Band, lateral collateral ligament and Biceps Femoris form a "Z"
    2. Start in-line with the IT Band at the anterolateral knee
    3. Keep probe fixed at the proximal end and pivot the distal end to overly the lateral collateral ligament
    4. Keep probe fixed at the distal end and pivot the proximal end to overly the biceps femoris
  4. Components
    1. Iliotibial Band (IT Band)
      1. Anterior (inserts at tibia)
    2. Lateral collateral ligament
      1. Lies posterior to IT Band
        1. Slide probe posteriorly until femur develops popliteal notch (with popliteal tendon)
        2. Slide probe inferiorly down distal femur over the joint space to visualize the fibular head
      2. Lateral collateral ligament (LCL) will be immediately overlying the joint space (femur-fibula)
        1. LCL inserts at fibula (shares fibular insertion with biceps femoris)
    3. Biceps femoris
      1. Inserts at fibula (shares fibular insertion with IT Band)
    4. Lateral Meniscus
      1. Suboptimal evaluation (poor sensitivity for pathology compared with gold standard MRI)
      2. Peripheral meniscal tear may be visualized

VII. Technique: Posterior Knee Ultrasound

  1. Positioning
    1. Patient lies prone with foot propped on pillow
    2. Ultrasound probe in short axis (SAX) with indicator directed medially
  2. Components
    1. Baker's Cyst
      1. Between semitendinosis, semimembranosus (medial) and medial gastrocnemius
    2. Posterior Collateral Ligament
      1. Typically non-diagnostic views as does not visualize tibial insertion
    3. Peroneal nerve
    4. Nerurovascular bundle (popliteal vein, popliteal artery)

VIII. References

  1. Mazzola (2016) GCUS Musculoskeletal Ultrasound Course, St. Pete's Beach, FL
  2. Moore (2013) Lower Extremity Ultrasound Video, Gulf Coast Ultrasound

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