What is the initial physical examination approach for a patient presenting with unilateral knee pain?

Physical Examination Template for Unilateral Knee Pain

The initial physical examination for unilateral knee pain should follow a systematic approach including inspection, palpation, range of motion assessment, and special tests to identify the specific pathology causing the pain. 1, 2

Initial Inspection

• Compare affected knee with unaffected side (always examine uninjured knee first for baseline) 3
• Observe for:
  • Swelling/effusion
  • Erythema
  • Deformity
  • Muscle atrophy (particularly quadriceps)
  • Gait pattern
  • Alignment (varus/valgus)

Palpation

• Joint line tenderness (83% sensitivity, 83% specificity for meniscal tears) 1
• Patellar borders and facets
• Tibial tubercle
• Femoral condyles
• Fibular head
• Popliteal fossa (for Baker's cyst)
• Pes anserine area
• Quadriceps and patellar tendons

Range of Motion Assessment

• Active and passive knee flexion and extension
• Compare with contralateral side
• Note any pain, crepitus, or mechanical symptoms during movement

Special Tests

Meniscal Tests

• McMurray Test:

  • Technique: With patient supine, flex knee fully, then externally rotate foot (for medial meniscus) or internally rotate foot (for lateral meniscus) while extending the knee
  • Positive: Pain or click along joint line
  • Indicates: Meniscal tear (61% sensitivity, 84% specificity) 1

• Apley Grind Test:

  • Technique: Patient prone, knee flexed 90°, apply axial compression while rotating the tibia
  • Positive: Pain with compression and rotation
  • Indicates: Meniscal tear

Ligament Tests

• Anterior Drawer Test:

  • Technique: Patient supine, knee flexed 90°, pull tibia forward
  • Positive: Excessive anterior tibial translation
  • Indicates: ACL injury

• Lachman Test:

  • Technique: Patient supine, knee flexed 20-30°, stabilize femur with one hand while pulling tibia forward with other
  • Positive: Excessive anterior tibial translation with soft endpoint
  • Indicates: ACL injury (more sensitive than anterior drawer)

• Posterior Drawer Test:

  • Technique: Patient supine, knee flexed 90°, push tibia posteriorly
  • Positive: Excessive posterior tibial translation
  • Indicates: PCL injury

• Valgus Stress Test (at 0° and 30° flexion):

  • Technique: Apply valgus force to knee while stabilizing thigh
  • Positive: Excessive medial opening
  • Indicates: MCL injury

• Varus Stress Test (at 0° and 30° flexion):

  • Technique: Apply varus force to knee while stabilizing thigh
  • Positive: Excessive lateral opening
  • Indicates: LCL injury

Patellofemoral Tests

• Patellar Apprehension Test:

  • Technique: Push patella laterally while extending knee
  • Positive: Patient shows apprehension or resists movement
  • Indicates: Patellar instability

• Patellar Grind Test (Clarke's Sign):

  • Technique: Press down on superior pole of patella while asking patient to contract quadriceps
  • Positive: Pain with quadriceps contraction
  • Indicates: Patellofemoral pain syndrome

• Single-Leg Squat:

  • Technique: Patient performs partial squat on affected leg
  • Positive: Pain, particularly anterior knee pain (91% sensitive, 50% specific for patellofemoral pain) 1
  • Indicates: Patellofemoral pain syndrome, dynamic knee valgus

Additional Assessments

• Bounce Test (for meniscal tears):

  • Technique: Fully flex knee then quickly extend
  • Positive: Pain or inability to fully extend
  • Indicates: Meniscal tear, particularly bucket-handle tear

• Thessaly Test:

  • Technique: Patient stands on affected leg with slight knee flexion, rotates body internally and externally
  • Positive: Pain or mechanical symptoms
  • Indicates: Meniscal tear

• Hip and Lumbar Spine Examination:

  • Always assess hip and lumbar spine as sources of referred knee pain, especially when knee exam is unremarkable 4

Red Flags Requiring Urgent Referral

• Severe pain, swelling, and instability after acute trauma
• Inability to bear weight
• Signs of joint infection (fever, erythema, warmth, severe pain with limited motion)
• Locked knee (true inability to fully extend) 5

Interpretation of Findings

• Joint line tenderness + positive McMurray test suggests meniscal tear
• Anterior knee pain during squat suggests patellofemoral pain syndrome (common in patients <40 years) 1
• Activity-related pain with minimal morning stiffness (<30 min) in patients >45 years suggests osteoarthritis (95% sensitivity, 69% specificity) 1
• Positive ligament tests indicate corresponding ligament injuries requiring further evaluation

Remember that physical examination findings should be correlated with history and, when indicated, appropriate imaging to establish a definitive diagnosis and guide management.