II. Indications

  1. Evaluate for Knee Collateral Ligament instability

III. Patient Position

  1. Patient lies supine on table
  2. Lower thigh rests on table edge, leg hangs off table

IV. Technique

  1. Perform each stress in two positions
    1. Knee in 0 degrees (full extension)
      1. Knee stabilized by PCL and bony articulation
    2. Knee in 30 degrees of flexion
      1. Isolates collateral ligament for evaluation
  2. Stabilize lower thigh with one hand
  3. Apply gentle stress at patient's ankle or foot
    1. Valgus stress tests medial collateral ligament
    2. Varus stress tests lateral collateral ligament
  4. Repeat test with gentle rocking motion
  5. Images
    1. orthoKneeValgusStress30.jpg
    2. orthoKneeVarusStress30.jpg

V. Precautions: Varus Stress Test

  1. Varus Stress Test may give False Positive result
    1. Femur rolls externally if not supported
    2. Slight knee flexion may allow for laxity
  2. Stabilize ipsilateral ankle to isolate knee
    1. Sit on edge of table
    2. Patient's ankle rests on examiner's upper knee

VI. Interpretation: Positive Test implies Instability

  1. See Ligamentous Sprain for laxity grading
  2. Laxity on Varus stress suggests Knee LCL Tear
  3. Laxity on valgus stress suggests Knee MCL Tear

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