Endgames Case Review

Knee pain in a 15 year old boy

BMJ 2017; 357 doi: https://doi.org/10.1136/bmj.j2749 (Published 22 June 2017) Cite this as: BMJ 2017;357:j2749
  1. Robert Miller, foundation doctor1,
  2. Oliver Beaumont, foundation doctor1,
  3. Jakob van Oldenrijk, consultant orthopaedic surgeon2
  1. 1Oxford University Hospitals, NHS Foundation Trust, Oxford, UK
  2. 2Erasmus University Medical Centre, Rotterdam, Netherlands
  1. Correspondence to R Miller robmiller90{at}gmail.com

A 15 year old boy presented after injuring his left knee while carrying a tray of food at a fast food restaurant. He felt his left knee “wobble” and immediately fell to the floor, unable to bear weight due to pain. On presentation to the emergency department, examination showed a laterally dislocated patella, which was reduced.

After reduction, examination showed a moderate effusion with some pain on palpation focused around the medial patellofemoral ligament. Range of movement was reduced to an extension-flexion of 0/10/60 degrees. Tests for ligamentous injury were unremarkable and the patient was able to resume weight bearing with the aid of crutches.

He had a Beighton score of 6, where 9 is a maximum score indicating joint laxity, despite having no history of joint dislocations. His medical history included chronic fatigue syndrome.

On follow-up two weeks later, the patient complained of intermittent locking in the left knee since the injury. On examination there was a joint effusion and a palpable loose body under the patella.

Questions

  • 1. Do the original radiographs (fig 1) show any abnormalities, and what further imaging should be considered for this patient?

  • 2. What are the risk factors for this injury?

  • 3. What are the management options for this patient?

Fig 1 Anteroposterior (1) and lateral (2) radiographs after patella reduction at initial presentation

Answers

1. Do the original radiographs (fig 1⇑) show any abnormalities, and what further imaging should be considered for this patient?

Short answer

The original radiographs show a lipohaemarthrosis and an osteochondral fragment (fig 2). Further imaging could include additional plain radiographs, a computed tomography (CT) scan to delineate bony injuries, and a magnetic resonance imaging (MRI) scan for soft tissue injuries.

Fig 2 Annotated anteroposterior (1) and lateral …

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