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Traumatic knee injury

BMJ 2013; 347 doi: https://doi.org/10.1136/bmj.f5303 (Published 23 September 2013) Cite this as: BMJ 2013;347:f5303
  1. G Stenhouse, specialist registrar, radiology,
  2. M Walker, consultant musculoskeletal radiologist,
  3. C Gupta, consultant orthopaedic surgeon,
  4. M Khanna, consultant musculoskeletal radiologist
  1. 1Department of Radiology, St Mary’s Hospital, Imperial NHS, London W21NY, UK
  1. Correspondence to: G Stenhouse gregors45{at}gmail.com

A 44 year old man injured his left knee while walking his dog in the park. He collided with two dogs who were chasing a ball; the main impact was on the anteromedial aspect of the left knee. Immediately after the injury he was in intense pain, the knee was swollen, and he was unable to bear weight. At presentation to the emergency department, examination showed a large effusion at the knee joint and tenderness over the anteromedial aspect of the joint. The range of movement at the knee was 30-60° and the knee was locked.

Findings on anterior and posterior draw testing were normal and valgus and varus stress testing did not identify ligamentous laxity. Lateral gliding of the patella caused considerable discomfort. Initially, he underwent radiography of the knee (figs 1 and 2). Subsequent magnetic resonance imaging (MRI) showed a classic pattern of bone marrow oedema along the medial patella facet and lateral femoral condyle, which is typical of a transient dislocation of the patella.

Fig 1 Lateral radiograph of left knee

Fig 2 Anterioposterior radiograph of left knee

Questions

  • 1 What abnormalities do the radiographs show?

  • 2 What are the indications for further imaging with MRI in acute knee injury?

  • 3 What predisposing risk factors for this condition should be considered?

  • 4 What are the management options?

Answers

1 What abnormalities do the radiographs show?

Short answer

A large knee joint effusion and a bone fragment in the anterior knee joint.

Long answer

When evaluating radiographs in patients who have experienced trauma, at least two views are needed (anterioposterior and lateral). The horizontal beam lateral view allows identification of …

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