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X-ray to Physical Exam: Knee

Matthew DeLaney, MD, FACEP, FAAEM, Mike Weinstock, MD, and Arun Sayal, MD
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18:21

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Matt and Mike sit down with Dr. Arun Sayal to discuss the evaluation of acute knee injuries in the urgent care. All knee injuries should be evaluated for knee stability and fractures to determine the need for prompt orthopedic consultation. Although commonly applied, knee immobilizers are not needed for most soft tissue injuries of the knee.

Pearls:

  • When getting a history on a patient with knee pain, consider:  patient age, mechanism/forces applied, and prior injuries.

  • The straight leg raise test is critical for ruling out a quadriceps or patellar tendon rupture.

  • Ligament assessment of the knee should answer 1 question:  is the knee stable or unstable?

  • Knee immobilizers can cause more harm than good in patients with stable knee injuries.

 

  • The acute knee exam is one of the more dissatisfying musculoskeletal exams we do in urgent care.

    • Patients are in pain, x-rays are negative, and we often diagnose a soft tissue injury without much clarity as to what is really going on.

    • We can serve patients better if we are a little more thoughtful of what the differential might be and how we get to those points. 

  • History

    • Age  

      • Younger people tend to have overuse injuries. Older ones have issues related to osteoarthritis.

    • Mechanism  

      • Valgus stress → MCL injury (if younger), lateral tibial plateau fracture (if elderly)

      • Twist and pop → ACL tear

      • Sudden contraction → patellar tendon or quadriceps rupture

    • Events after

      • Timing of swelling can help narrow the differential.

    • Prior injuries

  • Exam

    • Straight leg raise

      • Can the patient elevate their heel off the bed when supine or straighten their knee if legs are hanging over the bed?

      • Assesses patellar and quadriceps tendons.

      • May be equivocal if the patient has severe pain.

    • Feel for tenderness

      • If you can’t reproduce the pain with touching the knee, consider referred pain due to hip fracture, osteoarthritis, or slipped capital femoral epiphysis.

    • Ligament assessment

      • Should be done in the bed with a roll under the distal femur. This helps you manipulate the tibia to assess stability.

      • Focus on identifying unstable injuries, most significantly a knee dislocation (which tears multiple ligaments)

        • Knee dislocation spontaneously reduces 50% of the time and carries significant risk of vascular injury.

  • Knee x-rays

    • Standard views are AP and lateral +/- patellar view +/- obliques (to assess tibial plateau)

    • Consider standing films in older patients if worried about degenerative processes.

    • Fractures:

      • Patella

      • Tibial plateau (lateral more common)

      • Segond (avulsion off the lateral aspect of the proximal tibia, high specificity for ACL tear)

      • Tibial spine fracture (due to ACL tear)

      • Femoral condyles

    • High or low riding patella may indicate a quadriceps or patellar tendon tear

  • Management

    • Knee immobilizer only for:

      • Patellar fracture

      • Quadriceps or patellar tendon rupture

      • Patellar dislocation

    • If a stable soft tissue injury (ie. ACL, MCL. meniscus):

      • Can weight bear

      • Compression bandage and crutches as needed

      • Avoid knee immobilizers 

        • If you do dispense one, advise that they use it only when weight-bearing

        • Use may lead to joint stiffness and muscle atrophy

      • Encourage ROM exercises

 

References:


*Knee Immobilizer Video*


  1. Bunt C, et al. Knee Pain in Adults and Adolescents: The Initial Evaluation. Am Fam Physician. 2018;98(9):576-585. PMID: 30325638

Dana L. -

Great discussion. Are there times where you wouldn't feel the need to perform an xray? For example, I recently seen a patient who injured his knee a year ago playing football when he landed "wrong." He's been walking fine and was never evaluated after his injury. He came to the clinic after jumping off the last step of a truck and now has very mild knee pain with certain activities. Assessment was not impressive w/no pain with ROM, no swelling etc. What would be the appropriate treatment for this patient?

Mike W., MD -

Certainly needs to be individulaized and with nontraumatic pain the yield will be SUPER low! With trauma a year ago I do wonder about a loose body, non healed fx, avulsion fx, etc but of course will depend on your exam and index of suspicion.
M

Dana L. -

I had very low suspicion , based off of my assessment, of any serious injury. We opted to ACE wrap, RICE and Ortho referral. I'll keep your pointers in mind for further knee injuries. Thank you.

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Hippo Urgent Care Written Summary April 2021 306 KB - PDF

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