The Case: A 28-year-old female presented to the ED after falling down 2 stairs and landing on her left knee. She complained of severe pain to her left knee and inability to bear weight on her left leg. Examination revealed a moderate left knee effusion, diffuse tenderness, and an inability to bear weight
L Knee XR Was Performed:
IMPRESSION: No acute fracture. Moderate left knee joint effusion seen on the lateral view (not pictured).
On re-evaluation, the patient had persistent knee pain and demonstrated a continued inability to bear weight. A CT scan of her left knee without contrast was ordered.
IMPRESSION: Comminuted displaced fracture of the lateral tibial plateau.
The patient was placed in a knee immobilizer, given crutches, and told not to bear weight. She was subsequently evaluated by the orthopaedic service and scheduled for an outpatient surgical repair.
Why it matters:
Tibial plateau fractures are often difficult to appreciate on plain radiographs and when suspicion is high, a CT scan or MRI may be required to make the diagnosis. In one study, plain radiographs were 83% sensitive for the detection of knee fractures, compared to a 100% sensitivity for CT scan [1]. Emergency clinicians should consider obtaining a CT scan for the detection of an occult tibial plateau fracture should the patient have an inability to bear weight, significant effusion or an athrocentesis or plain radiogragh demonstrating lipohemarthrosis. Alternatively, keep the patient non weight bearing until follow up can be arranged and provide instructions to the patient explaining the potential limitations of plain radiographs.
Missing a tibial plateau fracture can lead to delay in treatment and abnormal loading of the joint. This can result in limitation of knee movements, early arthritis and deformity [2]. These patients typically require prompt orthopaedic assessment and the majority will undergo surgical repair.
Written by:
Dr. Kevin Boubouleix, MD
Emergency Medicine, PGY-3
Cook County Health
Reviewed by:
Dr. Scott Sherman, MD
Associate Program Director
Cook County Health
References:
Mustonen AO, Koskinen SK, Kiuru MJ. Acute knee trauma: analysis of multidetector computed tomography findings and comparison with conventional radiography. Acta Radiol 2005;46:866-74.
Anderson, A. N. (2020). A Retrospective Review of the Clinical Significance of Knee Effusions on X-ray Imaging and the Relation to Occult Tibial Plateau Fractures. Annals of Emergency Medicine, 76(4), 45–45.