Acute knee injury

Background

Knee ligaments

Knee anatomy

• Anterior Cruciate Ligament
  • Limits anterior translation of tibia
  • 75% of all hemarthroses are caused by disruption of ACL
• Posterior Cruciate Ligament
  • Limits posterior translation of tibia
  • Isolated injuries are rare
• Medial Collateral Ligament
  • Provide restraint against valgus (outward) stress
• Lateral Collateral Ligament
  • Provide restraint against varus (inward) stress

Clinical Features

• Acute trauma and pain to knee

Differential Diagnosis

Knee diagnoses

Acute knee injury

• Knee dislocation
• Knee fractures
  • Patella fracture
  • Segond fracture
  • Tibial plateau fracture
• Meniscus and ligament knee injuries
• Patella dislocation
• Patellar tendonitis
• Patellar tendon rupture
• Quadriceps tendon rupture

Nontraumatic/Subacute

• Arthritis
• Gout and Pseudogout
• Osgood-Schlatter disease
• Patellofemoral syndrome (Runner's Knee)
• Patellar tendonitis (Jumper's knee)
• Pes anserine bursitis
• Popliteal cyst (Bakers cyst)
• Prepatellar bursitis (nonseptic)
• Septic bursitis
• Septic joint
• DVT

Evaluation

Ottawa knee rules

Ottawa knee rules points of tenderness

X-ray is only required in patients who have an acute injury and one or more of the following:

• Age >55
• Isolated tenderness of the patella
• Tenderness at the fibular head
• Inability flex to 90 degrees
• Inability to walk 4 steps BOTH immediately after the injury and in the ED

Knee x-rays

• Anteroposterior and lateral views
  • Consider sunrise if pain over patella

Management

• If xrays are positive (when indicated)
  • Treat underlying condition
• If xrays are negative or not indicated Ottawa knee rules
  • Do full knee exam to check for ligamentous/meniscal instability:
    • Negative exam → RICE
    • Positive exam or unable to evaluate secondary to pain/swelling → knee brace + RICE

Disposition

• Depends on diagnosis; most often results in outpatient ortho referral

See Also

• Knee diagnoses