Intra-articular gas

Intra-articular gas or air (pneumarthrosis) can occur from a number of varied pathologies and should be interpreted according to the clinical context.

Causes include

• trauma 
  • compound injury with gas entering from the outer surface
    • can occur in with a pneumolipohaemarthrosis
• surgical intra-articular intervention
  • introduction of gas through a needle
• infection
  • septic arthritis with gas forming organism
• normal variation in some situations
  • intra-articular vacuum phenomena 
    • e.g. vacuum phenomenon in shoulder