Primary bacterial pyomyositis associated with septic arthritis caused by Streptococcus pyogenes: a case report.

Pyomyositis is relatively rare in temperate climates. This is the first report of a case of calf pyomyositis associated with septic arthritis of the knee. This case illustrates that pyomyositis should be included in the differential diagnosis of a swollen, tender calf in an emergency setting. The other notable feature of this case is that the infective organism was not the usual Staphylococcus aureus but rather the relatively rarely involved Streptococcus pyogenes.