Medial thigh abscess mimicking septic arthritis of the knee: a report of two cases

Background

Septic arthritis of the knee joint requires prompt diagnosis and treatment for optimal outcomes. Pyomyositis with abscess formation is uncommon but may present with similar symptoms in the vicinity of a joint.

Objective

This report describes two cases of medial thigh abscess initially diagnosed and treated as septic arthritis, and highlights the need to make an accurate diagnosis.

Case Report

Two patients presenting with knee pain secondary to pyomyositis and abscess formation in the medial thigh were investigated with aspiration and treated subsequently with knee surgery, resulting in contamination of the knee joint in one case and delayed diagnosis with significant morbidity in both.

Conclusion

Failure to identify a soft tissue infection may lead to delayed diagnosis, misdirected treatment, and contamination of a normal joint. Diagnosis is best confirmed with thorough physical examination and specific imaging where available.